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ResourceBundle 类介绍（二）源码分析

ResourceBundle 用到了很多java设计模式，其中模板方法用的比较多，很多设计技巧值得研究学习，该类为抽象类，如下方法

ResourceBundle resource = ResourceBundle.getBundle(BASENAME, locale); 该方法返回一个实例，具体实例化延迟到

子类实现，是模板方法模式使用，当然还有很多值得学习，贴出源码:

/* * @(#)ResourceBundle.java 1.88 07/06/24 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ /* * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved * (C) Copyright IBM Corp. 1996 - 1999 - All Rights Reserved * * The original version of this source code and documentation * is copyrighted and owned by Taligent, Inc., a wholly-owned * subsidiary of IBM. These materials are provided under terms * of a License Agreement between Taligent and Sun. This technology * is protected by multiple US and International patents. * * This notice and attribution to Taligent may not be removed. * Taligent is a registered trademark of Taligent, Inc. * */ package java.util; import java.io.IOException; import java.io.InputStream; import java.lang.ref.ReferenceQueue; import java.lang.ref.SoftReference; import java.lang.ref.WeakReference; import java.net.JarURLConnection; import java.net.URL; import java.net.URLConnection; import java.security.AccessController; import java.security.PrivilegedAction; import java.security.PrivilegedActionException; import java.security.PrivilegedExceptionAction; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import java.util.jar.JarEntry; /** * * Resource bundles contain locale-specific objects. * When your program needs a locale-specific resource, * a String for example, your program can load it * from the resource bundle that is appropriate for the * current user's locale. In this way, you can write * program code that is largely independent of the user's * locale isolating most, if not all, of the locale-specific * information in resource bundles. * *

* This allows you to write programs that can: *

be easily localized, or translated, into different languages *
handle multiple locales at once *
be easily modified later to support even more locales *

* *

* Resource bundles belong to families whose members share a common base * name, but whose names also have additional components that identify * their locales. For example, the base name of a family of resource * bundles might be "MyResources". The family should have a default * resource bundle which simply has the same name as its family - * "MyResources" - and will be used as the bundle of last resort if a * specific locale is not supported. The family can then provide as * many locale-specific members as needed, for example a German one * named "MyResources_de". * *

* Each resource bundle in a family contains the same items, but the items have * been translated for the locale represented by that resource bundle. * For example, both "MyResources" and "MyResources_de" may have a * String that's used on a button for canceling operations. * In "MyResources" the String may contain "Cancel" and in * "MyResources_de" it may contain "Abbrechen". * *

* If there are different resources for different countries, you * can make specializations: for example, "MyResources_de_CH" contains objects for * the German language (de) in Switzerland (CH). If you want to only * modify some of the resources * in the specialization, you can do so. * *

* When your program needs a locale-specific object, it loads * the ResourceBundle class using the * {@link #getBundle(java.lang.String, java.util.Locale) getBundle} * method: *

 * ResourceBundle myResources = * ResourceBundle.getBundle("MyResources", currentLocale); *

* *

* Resource bundles contain key/value pairs. The keys uniquely * identify a locale-specific object in the bundle. Here's an * example of a ListResourceBundle that contains * two key/value pairs: *

 * public class MyResources extends ListResourceBundle { * protected Object[][] getContents() { * return new Object[][] { * // LOCALIZE THE SECOND STRING OF EACH ARRAY (e.g., "OK") * {"OkKey", "OK"}, * {"CancelKey", "Cancel"}, * // END OF MATERIAL TO LOCALIZE * }; * } * } *

* Keys are always Strings. * In this example, the keys are "OkKey" and "CancelKey". * In the above example, the values * are also Strings--"OK" and "Cancel"--but * they don't have to be. The values can be any type of object. * *

* You retrieve an object from resource bundle using the appropriate * getter method. Because "OkKey" and "CancelKey" * are both strings, you would use getString to retrieve them: *

 * button1 = new Button(myResources.getString("OkKey")); * button2 = new Button(myResources.getString("CancelKey")); *

* The getter methods all require the key as an argument and return * the object if found. If the object is not found, the getter method * throws a MissingResourceException. * *

* Besides getString, ResourceBundle also provides * a method for getting string arrays, getStringArray, * as well as a generic getObject method for any other * type of object. When using getObject, you'll * have to cast the result to the appropriate type. For example: *

 * int[] myIntegers = (int[]) myResources.getObject("intList"); *

* *

* The Java Platform provides two subclasses of ResourceBundle, * ListResourceBundle and PropertyResourceBundle, * that provide a fairly simple way to create resources. * As you saw briefly in a previous example, ListResourceBundle * manages its resource as a list of key/value pairs. * PropertyResourceBundle uses a properties file to manage * its resources. * *

* If ListResourceBundle or PropertyResourceBundle * do not suit your needs, you can write your own ResourceBundle * subclass. Your subclasses must override two methods: handleGetObject * and getKeys(). * *

ResourceBundle.Control

* * The {@link ResourceBundle.Control} class provides information necessary * to perform the bundle loading process by the getBundle * factory methods that take a ResourceBundle.Control * instance. You can implement your own subclass in order to enable * non-standard resource bundle formats, change the search strategy, or * define caching parameters. Refer to the descriptions of the class and the * {@link #getBundle(String, Locale, ClassLoader, Control) getBundle} * factory method for details. * *

Cache Management

* * Resource bundle instances created by the getBundle factory * methods are cached by default, and the factory methods return the same * resource bundle instance multiple times if it has been * cached. getBundle clients may clear the cache, manage the * lifetime of cached resource bundle instances using time-to-live values, * or specify not to cache resource bundle instances. Refer to the * descriptions of the {@linkplain #getBundle(String, Locale, ClassLoader, * Control) getBundle factory method}, {@link * #clearCache(ClassLoader) clearCache}, {@link * Control#getTimeToLive(String, Locale) * ResourceBundle.Control.getTimeToLive}, and {@link * Control#needsReload(String, Locale, String, ClassLoader, ResourceBundle, * long) ResourceBundle.Control.needsReload} for details. * *

Example

* * The following is a very simple example of a ResourceBundle * subclass, MyResources, that manages two resources (for a larger number of * resources you would probably use a Map). * Notice that you don't need to supply a value if * a "parent-level" ResourceBundle handles the same * key with the same value (as for the okKey below). *

 * // default (English language, United States) * public class MyResources extends ResourceBundle { * public Object handleGetObject(String key) { * if (key.equals("okKey")) return "Ok"; * if (key.equals("cancelKey")) return "Cancel"; * return null; * } * * public Enumeration getKeys() { * return Collections.enumeration(keySet()); * } * * // Overrides handleKeySet() so that the getKeys() implementation * // can rely on the keySet() value. * protected Set handleKeySet() { * return new HashSet(Arrays.asList("okKey", "cancelKey")); * } * } * * // German language * public class MyResources_de extends MyResources { * public Object handleGetObject(String key) { * // don't need okKey, since parent level handles it. * if (key.equals("cancelKey")) return "Abbrechen"; * return null; * } * * protected Set handleKeySet() { * return new HashSet(Arrays.asList("cancelKey")); * } * } *

* You do not have to restrict yourself to using a single family of * ResourceBundles. For example, you could have a set of bundles for * exception messages, ExceptionResources * (ExceptionResources_fr, ExceptionResources_de, ...), * and one for widgets, WidgetResource (WidgetResources_fr, * WidgetResources_de, ...); breaking up the resources however you like. * * @see ListResourceBundle * @see PropertyResourceBundle * @see MissingResourceException * @since JDK1.1 */ public abstract class ResourceBundle { /** initial size of the bundle cache */ private static final int INITIAL_CACHE_SIZE = 32; /** constant indicating that no resource bundle exists */ private static final ResourceBundle NONEXISTENT_BUNDLE = new ResourceBundle() { public Enumeration getKeys() { return null; } protected Object handleGetObject(String key) { return null; } public String toString() { return "NONEXISTENT_BUNDLE"; } }; /** * The cache is a map from cache keys (with bundle base name, locale, and * class loader) to either a resource bundle or NONEXISTENT_BUNDLE wrapped by a * BundleReference. * * The cache is a ConcurrentMap, allowing the cache to be searched * concurrently by multiple threads. This will also allow the cache keys * to be reclaimed along with the ClassLoaders they reference. * * This variable would be better named "cache", but we keep the old * name for compatibility with some workarounds for bug 4212439. */ private static final ConcurrentMap cacheList = new ConcurrentHashMap(INITIAL_CACHE_SIZE); /** * This ConcurrentMap is used to keep multiple threads from loading the * same bundle concurrently. The table entries are * where CacheKey is the key for the bundle that is under construction * and Thread is the thread that is constructing the bundle. * This list is manipulated in findBundleInCache and putBundleInCache. */ private static final ConcurrentMap underConstruction = new ConcurrentHashMap(); /** * Queue for reference objects referring to class loaders or bundles. */ private static final ReferenceQueue referenceQueue = new ReferenceQueue(); /** * The parent bundle of this bundle. * The parent bundle is searched by {@link #getObject getObject} * when this bundle does not contain a particular resource. */ protected ResourceBundle parent = null; /** * The locale for this bundle. */ private Locale locale = null; /** * The base bundle name for this bundle. */ private String name; /** * The flag indicating this bundle has expired in the cache. */ private volatile boolean expired; /** * The back link to the cache key. null if this bundle isn't in * the cache (yet) or has expired. */ private volatile CacheKey cacheKey; /** * A Set of the keys contained only in this ResourceBundle. */ private volatile Set keySet; /** * Sole constructor. (For invocation by subclass constructors, typically * implicit.) */ public ResourceBundle() { } /** * Gets a string for the given key from this resource bundle or one of its parents. * Calling this method is equivalent to calling *

* (String) {@link #getObject(java.lang.String) getObject}(key). *

* * @param key the key for the desired string * @exception NullPointerException if key is null * @exception MissingResourceException if no object for the given key can be found * @exception ClassCastException if the object found for the given key is not a string * @return the string for the given key */ public final String getString(String key) { return (String) getObject(key); } /** * Gets a string array for the given key from this resource bundle or one of its parents. * Calling this method is equivalent to calling *

* (String[]) {@link #getObject(java.lang.String) getObject}(key). *

* * @param key the key for the desired string array * @exception NullPointerException if key is null * @exception MissingResourceException if no object for the given key can be found * @exception ClassCastException if the object found for the given key is not a string array * @return the string array for the given key */ public final String[] getStringArray(String key) { return (String[]) getObject(key); } /** * Gets an object for the given key from this resource bundle or one of its parents. * This method first tries to obtain the object from this resource bundle using * {@link #handleGetObject(java.lang.String) handleGetObject}. * If not successful, and the parent resource bundle is not null, * it calls the parent's getObject method. * If still not successful, it throws a MissingResourceException. * * @param key the key for the desired object * @exception NullPointerException if key is null * @exception MissingResourceException if no object for the given key can be found * @return the object for the given key */ public final Object getObject(String key) { Object obj = handleGetObject(key); if (obj == null) { if (parent != null) { obj = parent.getObject(key); } if (obj == null) throw new MissingResourceException("Can't find resource for bundle " +this.getClass().getName() +", key "+key, this.getClass().getName(), key); } return obj; } /** * Returns the locale of this resource bundle. This method can be used after a * call to getBundle() to determine whether the resource bundle returned really * corresponds to the requested locale or is a fallback. * * @return the locale of this resource bundle */ public Locale getLocale() { return locale; } /* * Automatic determination of the ClassLoader to be used to load * resources on behalf of the client. N.B. The client is getLoader's * caller's caller. */ private static ClassLoader getLoader() { Class[] stack = getClassContext(); /* Magic number 2 identifies our caller's caller */ Class c = stack[2]; ClassLoader cl = (c == null) ? null : c.getClassLoader(); if (cl == null) { // When the caller's loader is the boot class loader, cl is null // here. In that case, ClassLoader.getSystemClassLoader() may // return the same class loader that the application is // using. We therefore use a wrapper ClassLoader to create a // separate scope for bundles loaded on behalf of the Java // runtime so that these bundles cannot be returned from the // cache to the application (5048280). cl = RBClassLoader.INSTANCE; } return cl; } private static native Class[] getClassContext(); /** * A wrapper of ClassLoader.getSystemClassLoader(). */ private static class RBClassLoader extends ClassLoader { private static final RBClassLoader INSTANCE = AccessController.doPrivileged( new PrivilegedAction() { public RBClassLoader run() { return new RBClassLoader(); } }); private static final ClassLoader loader = ClassLoader.getSystemClassLoader(); private RBClassLoader() { } public Class loadClass(String name) throws ClassNotFoundException { if (loader != null) { return loader.loadClass(name); } return Class.forName(name); } public URL getResource(String name) { if (loader != null) { return loader.getResource(name); } return ClassLoader.getSystemResource(name); } public InputStream getResourceAsStream(String name) { if (loader != null) { return loader.getResourceAsStream(name); } return ClassLoader.getSystemResourceAsStream(name); } } /** * Sets the parent bundle of this bundle. * The parent bundle is searched by {@link #getObject getObject} * when this bundle does not contain a particular resource. * * @param parent this bundle's parent bundle. */ protected void setParent(ResourceBundle parent) { assert parent != NONEXISTENT_BUNDLE; this.parent = parent; } /** * Key used for cached resource bundles. The key checks the base * name, the locale, and the class loader to determine if the * resource is a match to the requested one. The loader may be * null, but the base name and the locale must have a non-null * value. */ private static final class CacheKey implements Cloneable { // These three are the actual keys for lookup in Map. private String name; private Locale locale; private LoaderReference loaderRef; // bundle format which is necessary for calling // Control.needsReload(). private String format; // These time values are in CacheKey so that NONEXISTENT_BUNDLE // doesn't need to be cloned for caching. // The time when the bundle has been loaded private volatile long loadTime; // The time when the bundle expires in the cache, or either // Control.TTL_DONT_CACHE or Control.TTL_NO_EXPIRATION_CONTROL. private volatile long expirationTime; // Placeholder for an error report by a Throwable private Throwable cause; // Hash code value cache to avoid recalculating the hash code // of this instance. private int hashCodeCache; CacheKey(String baseName, Locale locale, ClassLoader loader) { this.name = baseName; this.locale = locale; if (loader == null) { this.loaderRef = null; } else { loaderRef = new LoaderReference(loader, referenceQueue, this); } calculateHashCode(); } String getName() { return name; } CacheKey setName(String baseName) { if (!this.name.equals(baseName)) { this.name = baseName; calculateHashCode(); } return this; } Locale getLocale() { return locale; } CacheKey setLocale(Locale locale) { if (!this.locale.equals(locale)) { this.locale = locale; calculateHashCode(); } return this; } ClassLoader getLoader() { return (loaderRef != null) ? loaderRef.get() : null; } public boolean equals(Object other) { if (this == other) { return true; } try { final CacheKey otherEntry = (CacheKey)other; //quick check to see if they are not equal if (hashCodeCache != otherEntry.hashCodeCache) { return false; } //are the names the same? if (!name.equals(otherEntry.name)) { return false; } // are the locales the same? if (!locale.equals(otherEntry.locale)) { return false; } //are refs (both non-null) or (both null)? if (loaderRef == null) { return otherEntry.loaderRef == null; } ClassLoader loader = loaderRef.get(); return (otherEntry.loaderRef != null) // with a null reference we can no longer find // out which class loader was referenced; so // treat it as unequal && (loader != null) && (loader == otherEntry.loaderRef.get()); } catch (NullPointerException e) { } catch (ClassCastException e) { } return false; } public int hashCode() { return hashCodeCache; } private void calculateHashCode() { hashCodeCache = name.hashCode() << 3; hashCodeCache ^= locale.hashCode(); ClassLoader loader = getLoader(); if (loader != null) { hashCodeCache ^= loader.hashCode(); } } public Object clone() { try { CacheKey clone = (CacheKey) super.clone(); if (loaderRef != null) { clone.loaderRef = new LoaderReference(loaderRef.get(), referenceQueue, clone); } // Clear the reference to a Throwable clone.cause = null; return clone; } catch (CloneNotSupportedException e) { //this should never happen throw new InternalError(); } } String getFormat() { return format; } void setFormat(String format) { this.format = format; } private void setCause(Throwable cause) { if (this.cause == null) { this.cause = cause; } else { // Override the cause if the previous one is // ClassNotFoundException. if (this.cause instanceof ClassNotFoundException) { this.cause = cause; } } } private Throwable getCause() { return cause; } public String toString() { String l = locale.toString(); if (l.length() == 0) { if (locale.getVariant().length() != 0) { l = "__" + locale.getVariant(); } else { l = "/"/""; } } return "CacheKey[" + name + ", lc=" + l + ", ldr=" + getLoader() + "(format=" + format + ")]"; } } /** * The common interface to get a CacheKey in LoaderReference and * BundleReference. */ private static interface CacheKeyReference { public CacheKey getCacheKey(); } /** * References to class loaders are weak references, so that they can be * garbage collected when nobody else is using them. The ResourceBundle * class has no reason to keep class loaders alive. */ private static final class LoaderReference extends WeakReference implements CacheKeyReference { private CacheKey cacheKey; LoaderReference(ClassLoader referent, ReferenceQueue q, CacheKey key) { super(referent, q); cacheKey = key; } public CacheKey getCacheKey() { return cacheKey; } } /** * References to bundles are soft references so that they can be garbage * collected when they have no hard references. */ private static final class BundleReference extends SoftReference implements CacheKeyReference { private CacheKey cacheKey; BundleReference(ResourceBundle referent, ReferenceQueue q, CacheKey key) { super(referent, q); cacheKey = key; } public CacheKey getCacheKey() { return cacheKey; } } /** * Gets a resource bundle using the specified base name, the default locale, * and the caller's class loader. Calling this method is equivalent to calling *

* getBundle(baseName, Locale.getDefault(), this.getClass().getClassLoader()), *

* except that getClassLoader() is run with the security * privileges of ResourceBundle. * See {@link #getBundle(String, Locale, ClassLoader) getBundle} * for a complete description of the search and instantiation strategy. * * @param baseName the base name of the resource bundle, a fully qualified class name * @exception java.lang.NullPointerException * if baseName is null * @exception MissingResourceException * if no resource bundle for the specified base name can be found * @return a resource bundle for the given base name and the default locale */ public static final ResourceBundle getBundle(String baseName) { return getBundleImpl(baseName, Locale.getDefault(), /* must determine loader here, else we break stack invariant */ getLoader(), Control.INSTANCE); } /** * Returns a resource bundle using the specified base name, the * default locale and the specified control. Calling this method * is equivalent to calling *

 * getBundle(baseName, Locale.getDefault(), * this.getClass().getClassLoader(), control), *

* except that getClassLoader() is run with the security * privileges of ResourceBundle. See {@link * #getBundle(String, Locale, ClassLoader, Control) getBundle} for the * complete description of the resource bundle loading process with a * ResourceBundle.Control. * * @param baseName * the base name of the resource bundle, a fully qualified class * name * @param control * the control which gives information for the resource bundle * loading process * @return a resource bundle for the given base name and the default * locale * @exception NullPointerException * if baseName or control is * null * @exception MissingResourceException * if no resource bundle for the specified base name can be found * @exception IllegalArgumentException * if the given control doesn't perform properly * (e.g., control.getCandidateLocales returns null.) * Note that validation of control is performed as * needed. * @since 1.6 */ public static final ResourceBundle getBundle(String baseName, Control control) { return getBundleImpl(baseName, Locale.getDefault(), /* must determine loader here, else we break stack invariant */ getLoader(), control); } /** * Gets a resource bundle using the specified base name and locale, * and the caller's class loader. Calling this method is equivalent to calling *

* getBundle(baseName, locale, this.getClass().getClassLoader()), *

* except that getClassLoader() is run with the security * privileges of ResourceBundle. * See {@link #getBundle(String, Locale, ClassLoader) getBundle} * for a complete description of the search and instantiation strategy. * * @param baseName * the base name of the resource bundle, a fully qualified class name * @param locale * the locale for which a resource bundle is desired * @exception NullPointerException * if baseName or locale is null * @exception MissingResourceException * if no resource bundle for the specified base name can be found * @return a resource bundle for the given base name and locale */ public static final ResourceBundle getBundle(String baseName, Locale locale) { return getBundleImpl(baseName, locale, /* must determine loader here, else we break stack invariant */ getLoader(), Control.INSTANCE); } /** * Returns a resource bundle using the specified base name, target * locale and control, and the caller's class loader. Calling this * method is equivalent to calling *

 * getBundle(baseName, targetLocale, this.getClass().getClassLoader(), * control), *

* except that getClassLoader() is run with the security * privileges of ResourceBundle. See {@link * #getBundle(String, Locale, ClassLoader, Control) getBundle} for the * complete description of the resource bundle loading process with a * ResourceBundle.Control. * * @param baseName * the base name of the resource bundle, a fully qualified * class name * @param targetLocale * the locale for which a resource bundle is desired * @param control * the control which gives information for the resource * bundle loading process * @return a resource bundle for the given base name and a * Locale in locales * @exception NullPointerException * if baseName, locales or * control is null * @exception MissingResourceException * if no resource bundle for the specified base name in any * of the locales can be found. * @exception IllegalArgumentException * if the given control doesn't perform properly * (e.g., control.getCandidateLocales returns null.) * Note that validation of control is performed as * needed. * @since 1.6 */ public static final ResourceBundle getBundle(String baseName, Locale targetLocale, Control control) { return getBundleImpl(baseName, targetLocale, /* must determine loader here, else we break stack invariant */ getLoader(), control); } /** * Gets a resource bundle using the specified base name, locale, and class loader. * *

* Conceptually, getBundle uses the following strategy for locating and instantiating * resource bundles: *

* getBundle uses the base name, the specified locale, and the default * locale (obtained from {@link java.util.Locale#getDefault() Locale.getDefault}) * to generate a sequence of candidate bundle names. * If the specified locale's language, country, and variant are all empty * strings, then the base name is the only candidate bundle name. * Otherwise, the following sequence is generated from the attribute * values of the specified locale (language1, country1, and variant1) * and of the default locale (language2, country2, and variant2): *

baseName + "_" + language1 + "_" + country1 + "_" + variant1 *
baseName + "_" + language1 + "_" + country1 *
baseName + "_" + language1 *
baseName + "_" + language2 + "_" + country2 + "_" + variant2 *
baseName + "_" + language2 + "_" + country2 *
baseName + "_" + language2 *
baseName *

* Candidate bundle names where the final component is an empty string are omitted. * For example, if country1 is an empty string, the second candidate bundle name is omitted. * *

* getBundle then iterates over the candidate bundle names to find the first * one for which it can instantiate an actual resource bundle. For each candidate * bundle name, it attempts to create a resource bundle: *

* First, it attempts to load a class using the candidate bundle name. * If such a class can be found and loaded using the specified class loader, is assignment * compatible with ResourceBundle, is accessible from ResourceBundle, and can be instantiated, * getBundle creates a new instance of this class and uses it as the result * resource bundle. *
* Otherwise, getBundle attempts to locate a property resource file. * It generates a path name from the candidate bundle name by replacing all "." characters * with "/" and appending the string ".properties". * It attempts to find a "resource" with this name using * {@link java.lang.ClassLoader#getResource(java.lang.String) ClassLoader.getResource}. * (Note that a "resource" in the sense of getResource has nothing to do with * the contents of a resource bundle, it is just a container of data, such as a file.) * If it finds a "resource", it attempts to create a new * {@link PropertyResourceBundle} instance from its contents. * If successful, this instance becomes the result resource bundle. *

* *

* If no result resource bundle has been found, a MissingResourceException * is thrown. * *

* Once a result resource bundle has been found, its parent chain is instantiated. * getBundle iterates over the candidate bundle names that can be * obtained by successively removing variant, country, and language * (each time with the preceding "_") from the bundle name of the result resource bundle. * As above, candidate bundle names where the final component is an empty string are omitted. * With each of the candidate bundle names it attempts to instantiate a resource bundle, as * described above. * Whenever it succeeds, it calls the previously instantiated resource * bundle's {@link #setParent(java.util.ResourceBundle) setParent} method * with the new resource bundle, unless the previously instantiated resource * bundle already has a non-null parent. * *

* getBundle caches instantiated resource bundles and * may return the same resource bundle instance multiple * times. * *

* The baseName argument should be a fully qualified class name. However, for * compatibility with earlier versions, Sun's Java SE Runtime Environments do not verify this, * and so it is possible to access PropertyResourceBundles by specifying a * path name (using "/") instead of a fully qualified class name (using "."). * *

* Example:
The following class and property files are provided: *

 * MyResources.class * MyResources.properties * MyResources_fr.properties * MyResources_fr_CH.class * MyResources_fr_CH.properties * MyResources_en.properties * MyResources_es_ES.class *

* The contents of all files are valid (that is, public non-abstract subclasses of ResourceBundle for * the ".class" files, syntactically correct ".properties" files). * The default locale is Locale("en", "GB"). *

* Calling getBundle with the shown locale argument values instantiates * resource bundles from the following sources: *

Locale("fr", "CH"): result MyResources_fr_CH.class, parent MyResources_fr.properties, parent MyResources.class *
Locale("fr", "FR"): result MyResources_fr.properties, parent MyResources.class *
Locale("de", "DE"): result MyResources_en.properties, parent MyResources.class *
Locale("en", "US"): result MyResources_en.properties, parent MyResources.class *
Locale("es", "ES"): result MyResources_es_ES.class, parent MyResources.class *

The file MyResources_fr_CH.properties is never used because it is hidden by * MyResources_fr_CH.class. Likewise, MyResources.properties is also hidden by * MyResources.class. * * @param baseName the base name of the resource bundle, a fully qualified class name * @param locale the locale for which a resource bundle is desired * @param loader the class loader from which to load the resource bundle * @return a resource bundle for the given base name and locale * @exception java.lang.NullPointerException * if baseName, locale, or loader is null * @exception MissingResourceException * if no resource bundle for the specified base name can be found * @since 1.2 */ public static ResourceBundle getBundle(String baseName, Locale locale, ClassLoader loader) { if (loader == null) { throw new NullPointerException(); } return getBundleImpl(baseName, locale, loader, Control.INSTANCE); } /** * Returns a resource bundle using the specified base name, target * locale, class loader and control. Unlike the {@linkplain * #getBundle(String, Locale, ClassLoader) getBundle * factory methods with no control argument}, the given * control specifies how to locate and instantiate resource * bundles. Conceptually, the bundle loading process with the given * control is performed in the following steps. * *

This factory method looks up the resource bundle in the cache for * the specified baseName, targetLocale and * loader. If the requested resource bundle instance is * found in the cache and the time-to-live periods of the instance and * all of its parent instances have not expired, the instance is returned * to the caller. Otherwise, this factory method proceeds with the * loading process below.
The {@link ResourceBundle.Control#getFormats(String) * control.getFormats} method is called to get resource bundle formats * to produce bundle or resource names. The strings * "java.class" and "java.properties" * designate class-based and {@linkplain PropertyResourceBundle * property}-based resource bundles, respectively. Other strings * starting with "java." are reserved for future extensions * and must not be used for application-defined formats. Other strings * designate application-defined formats.
The {@link ResourceBundle.Control#getCandidateLocales(String, * Locale) control.getCandidateLocales} method is called with the target * locale to get a list of candidate Locales for * which resource bundles are searched.
The {@link ResourceBundle.Control#newBundle(String, Locale, * String, ClassLoader, boolean) control.newBundle} method is called to * instantiate a ResourceBundle for the base bundle name, a * candidate locale, and a format. (Refer to the note on the cache * lookup below.) This step is iterated over all combinations of the * candidate locales and formats until the newBundle method * returns a ResourceBundle instance or the iteration has * used up all the combinations. For example, if the candidate locales * are Locale("de", "DE"), Locale("de") and * Locale("") and the formats are "java.class" * and "java.properties", then the following is the * sequence of locale-format combinations to be used to call * control.newBundle. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Locale
* format
*
Locale("de", "DE")
* java.class
*
Locale("de", "DE") java.properties
*
Locale("de") java.class
Locale("de") java.properties
Locale("")
* java.class
Locale("") java.properties
*
If the previous step has found no resource bundle, proceed to * Step 6. If a bundle has been found that is a base bundle (a bundle * for Locale("")), and the candidate locale list only contained * Locale(""), return the bundle to the caller. If a bundle * has been found that is a base bundle, but the candidate locale list * contained locales other than Locale(""), put the bundle on hold and * proceed to Step 6. If a bundle has been found that is not a base * bundle, proceed to Step 7.
The {@link ResourceBundle.Control#getFallbackLocale(String, * Locale) control.getFallbackLocale} method is called to get a fallback * locale (alternative to the current target locale) to try further * finding a resource bundle. If the method returns a non-null locale, * it becomes the next target locale and the loading process starts over * from Step 3. Otherwise, if a base bundle was found and put on hold in * a previous Step 5, it is returned to the caller now. Otherwise, a * MissingResourceException is thrown.
At this point, we have found a resource bundle that's not the * base bundle. If this bundle set its parent during its instantiation, * it is returned to the caller. Otherwise, its parent chain is * instantiated based on the list of candidate locales from which it was * found. Finally, the bundle is returned to the caller.

* *

During the resource bundle loading process above, this factory * method looks up the cache before calling the {@link * Control#newBundle(String, Locale, String, ClassLoader, boolean) * control.newBundle} method. If the time-to-live period of the * resource bundle found in the cache has expired, the factory method * calls the {@link ResourceBundle.Control#needsReload(String, Locale, * String, ClassLoader, ResourceBundle, long) control.needsReload} * method to determine whether the resource bundle needs to be reloaded. * If reloading is required, the factory method calls * control.newBundle to reload the resource bundle. If * control.newBundle returns null, the factory * method puts a dummy resource bundle in the cache as a mark of * nonexistent resource bundles in order to avoid lookup overhead for * subsequent requests. Such dummy resource bundles are under the same * expiration control as specified by control. * *

All resource bundles loaded are cached by default. Refer to * {@link Control#getTimeToLive(String,Locale) * control.getTimeToLive} for details. * * *

The following is an example of the bundle loading process with the * default ResourceBundle.Control implementation. * *

Conditions: *

Base bundle name: foo.bar.Messages *
Requested Locale: {@link Locale#ITALY}
Default Locale: {@link Locale#FRENCH}
Available resource bundles: * foo/bar/Messages_fr.properties and * foo/bar/Messages.properties

* *

First, getBundle tries loading a resource bundle in * the following sequence. * *

class foo.bar.Messages_it_IT *
file foo/bar/Messages_it_IT.properties *
class foo.bar.Messages_it
file foo/bar/Messages_it.properties
class foo.bar.Messages
file foo/bar/Messages.properties

* *

At this point, getBundle finds * foo/bar/Messages.properties, which is put on hold * because it's the base bundle. getBundle calls {@link * Control#getFallbackLocale(String, Locale) * control.getFallbackLocale("foo.bar.Messages", Locale.ITALY)} which * returns Locale.FRENCH. Next, getBundle * tries loading a bundle in the following sequence. * *

class foo.bar.Messages_fr
file foo/bar/Messages_fr.properties
class foo.bar.Messages
file foo/bar/Messages.properties

* *

getBundle finds * foo/bar/Messages_fr.properties and creates a * ResourceBundle instance. Then, getBundle * sets up its parent chain from the list of the candiate locales. Only * foo/bar/Messages.properties is found in the list and * getBundle creates a ResourceBundle instance * that becomes the parent of the instance for * foo/bar/Messages_fr.properties. * * @param baseName * the base name of the resource bundle, a fully qualified * class name * @param targetLocale * the locale for which a resource bundle is desired * @param loader * the class loader from which to load the resource bundle * @param control * the control which gives information for the resource * bundle loading process * @return a resource bundle for the given base name and locale * @exception NullPointerException * if baseName, targetLocale, * loader, or control is * null * @exception MissingResourceException * if no resource bundle for the specified base name can be found * @exception IllegalArgumentException * if the given control doesn't perform properly * (e.g., control.getCandidateLocales returns null.) * Note that validation of control is performed as * needed. * @since 1.6 */ public static ResourceBundle getBundle(String baseName, Locale targetLocale, ClassLoader loader, Control control) { if (loader == null || control == null) { throw new NullPointerException(); } return getBundleImpl(baseName, targetLocale, loader, control); } private static ResourceBundle getBundleImpl(String baseName, Locale locale, ClassLoader loader, Control control) { if (locale == null || control == null) { throw new NullPointerException(); } // We create a CacheKey here for use by this call. The base // name and loader will never change during the bundle loading // process. We have to make sure that the locale is set before // using it as a cache key. CacheKey cacheKey = new CacheKey(baseName, locale, loader); ResourceBundle bundle = null; // Quick lookup of the cache. BundleReference bundleRef = cacheList.get(cacheKey); if (bundleRef != null) { bundle = bundleRef.get(); bundleRef = null; } // If this bundle and all of its parents are valid (not expired), // then return this bundle. If any of the bundles is expired, we // don't call control.needsReload here but instead drop into the // complete loading process below. if (isValidBundle(bundle) && hasValidParentChain(bundle)) { return bundle; } // No valid bundle was found in the cache, so we need to load the // resource bundle and its parents. boolean isKnownControl = (control == Control.INSTANCE) || (control instanceof SingleFormatControl); List formats = control.getFormats(baseName); if (!isKnownControl && !checkList(formats)) { throw new IllegalArgumentException("Invalid Control: getFormats"); } ResourceBundle baseBundle = null; for (Locale targetLocale = locale; targetLocale != null; targetLocale = control.getFallbackLocale(baseName, targetLocale)) { List candidateLocales = control.getCandidateLocales(baseName, targetLocale); if (!isKnownControl && !checkList(candidateLocales)) { throw new IllegalArgumentException("Invalid Control: getCandidateLocales"); } bundle = findBundle(cacheKey, candidateLocales, formats, 0, control, baseBundle); // If the loaded bundle is the base bundle and exactly for the // requested locale or the only candidate locale, then take the // bundle as the resulting one. If the loaded bundle is the base // bundle, it's put on hold until we finish processing all // fallback locales. if (isValidBundle(bundle)) { boolean isBaseBundle = Locale.ROOT.equals(bundle.locale); if (!isBaseBundle || bundle.locale.equals(locale) || (candidateLocales.size() == 1 && bundle.locale.equals(candidateLocales.get(0)))) { break; } // If the base bundle has been loaded, keep the reference in // baseBundle so that we can avoid any redundant loading in case // the control specify not to cache bundles. if (isBaseBundle && baseBundle == null) { baseBundle = bundle; } } } if (bundle == null) { if (baseBundle == null) { throwMissingResourceException(baseName, locale, cacheKey.getCause()); } bundle = baseBundle; } return bundle; } /** * Checks if the given List is not null, not empty, * not having null in its elements. */ private static final boolean checkList(List a) { boolean valid = (a != null && a.size() != 0); if (valid) { int size = a.size(); for (int i = 0; valid && i < size; i++) { valid = (a.get(i) != null); } } return valid; } private static final ResourceBundle findBundle(CacheKey cacheKey, List candidateLocales, List formats, int index, Control control, ResourceBundle baseBundle) { Locale targetLocale = candidateLocales.get(index); ResourceBundle parent = null; if (index != candidateLocales.size() - 1) { parent = findBundle(cacheKey, candidateLocales, formats, index + 1, control, baseBundle); } else if (baseBundle != null && Locale.ROOT.equals(targetLocale)) { return baseBundle; } // Before we do the real loading work, see whether we need to // do some housekeeping: If references to class loaders or // resource bundles have been nulled out, remove all related // information from the cache. Object ref; while ((ref = referenceQueue.poll()) != null) { cacheList.remove(((CacheKeyReference)ref).getCacheKey()); } // flag indicating the resource bundle has expired in the cache boolean expiredBundle = false; // First, look up the cache to see if it's in the cache, without // declaring beginLoading. cacheKey.setLocale(targetLocale); ResourceBundle bundle = findBundleInCache(cacheKey, control); if (isValidBundle(bundle)) { expiredBundle = bundle.expired; if (!expiredBundle) { // If its parent is the one asked for by the candidate // locales (the runtime lookup path), we can take the cached // one. (If it's not identical, then we'd have to check the // parent's parents to be consistent with what's been // requested.) if (bundle.parent == parent) { return bundle; } // Otherwise, remove the cached one since we can't keep // the same bundles having different parents. BundleReference bundleRef = cacheList.get(cacheKey); if (bundleRef != null && bundleRef.get() == bundle) { cacheList.remove(cacheKey, bundleRef); } } } if (bundle != NONEXISTENT_BUNDLE) { CacheKey constKey = (CacheKey) cacheKey.clone(); try { // Try declaring loading. If beginLoading() returns true, // then we can proceed. Otherwise, we need to take a look // at the cache again to see if someone else has loaded // the bundle and put it in the cache while we've been // waiting for other loading work to complete. while (!beginLoading(constKey)) { bundle = findBundleInCache(cacheKey, control); if (bundle == null) { continue; } if (bundle == NONEXISTENT_BUNDLE) { // If the bundle is NONEXISTENT_BUNDLE, the bundle doesn't exist. return parent; } expiredBundle = bundle.expired; if (!expiredBundle) { if (bundle.parent == parent) { return bundle; } BundleReference bundleRef = cacheList.get(cacheKey); if (bundleRef != null && bundleRef.get() == bundle) { cacheList.remove(cacheKey, bundleRef); } } } try { bundle = loadBundle(cacheKey, formats, control, expiredBundle); if (bundle != null) { if (bundle.parent == null) { bundle.setParent(parent); } bundle.locale = targetLocale; bundle = putBundleInCache(cacheKey, bundle, control); return bundle; } // Put NONEXISTENT_BUNDLE in the cache as a mark that there's no bundle // instance for the locale. putBundleInCache(cacheKey, NONEXISTENT_BUNDLE, control); } finally { endLoading(constKey); } } finally { if (constKey.getCause() instanceof InterruptedException) { Thread.currentThread().interrupt(); } } } assert underConstruction.get(cacheKey) != Thread.currentThread(); return parent; } private static final ResourceBundle loadBundle(CacheKey cacheKey, List formats, Control control, boolean reload) { assert underConstruction.get(cacheKey) == Thread.currentThread(); // Here we actually load the bundle in the order of formats // specified by the getFormats() value. Locale targetLocale = cacheKey.getLocale(); ResourceBundle bundle = null; int size = formats.size(); for (int i = 0; i < size; i++) { String format = formats.get(i); try { bundle = control.newBundle(cacheKey.getName(), targetLocale, format, cacheKey.getLoader(), reload); } catch (LinkageError error) { // We need to handle the LinkageError case due to // inconsistent case-sensitivity in ClassLoader. // See 6572242 for details. cacheKey.setCause(error); } catch (Exception cause) { cacheKey.setCause(cause); } if (bundle != null) { // Set the format in the cache key so that it can be // used when calling needsReload later. cacheKey.setFormat(format); bundle.name = cacheKey.getName(); bundle.locale = targetLocale; // Bundle provider might reuse instances. So we should make // sure to clear the expired flag here. bundle.expired = false; break; } } assert underConstruction.get(cacheKey) == Thread.currentThread(); return bundle; } private static final boolean isValidBundle(ResourceBundle bundle) { return bundle != null && bundle != NONEXISTENT_BUNDLE; } /** * Determines whether any of resource bundles in the parent chain, * including the leaf, have expired. */ private static final boolean hasValidParentChain(ResourceBundle bundle) { long now = System.currentTimeMillis(); while (bundle != null) { if (bundle.expired) { return false; } CacheKey key = bundle.cacheKey; if (key != null) { long expirationTime = key.expirationTime; if (expirationTime >= 0 && expirationTime <= now) { return false; } } bundle = bundle.parent; } return true; } /** * Declares the beginning of actual resource bundle loading. This method * returns true if the declaration is successful and the current thread has * been put in underConstruction. If someone else has already begun * loading, this method waits until that loading work is complete and * returns false. */ private static final boolean beginLoading(CacheKey constKey) { Thread me = Thread.currentThread(); Thread worker; // We need to declare by putting the current Thread (me) to // underConstruction that we are working on loading the specified // resource bundle. If we are already working the loading, it means // that the resource loading requires a recursive call. In that case, // we have to proceed. (4300693) if (((worker = underConstruction.putIfAbsent(constKey, me)) == null) || worker == me) { return true; } // If someone else is working on the loading, wait until // the Thread finishes the bundle loading. synchronized (worker) { while (underConstruction.get(constKey) == worker) { try { worker.wait(); } catch (InterruptedException e) { // record the interruption constKey.setCause(e); } } } return false; } /** * Declares the end of the bundle loading. This method calls notifyAll * for those who are waiting for this completion. */ private static final void endLoading(CacheKey constKey) { // Remove this Thread from the underConstruction map and wake up // those who have been waiting for me to complete this bundle // loading. Thread me = Thread.currentThread(); assert (underConstruction.get(constKey) == me); underConstruction.remove(constKey); synchronized (me) { me.notifyAll(); } } /** * Throw a MissingResourceException with proper message */ private static final void throwMissingResourceException(String baseName, Locale locale, Throwable cause) { // If the cause is a MissingResourceException, avoid creating // a long chain. (6355009) if (cause instanceof MissingResourceException) { cause = null; } throw new MissingResourceException("Can't find bundle for base name " + baseName + ", locale " + locale, baseName + "_" + locale, // className "", // key cause); } /** * Finds a bundle in the cache. Any expired bundles are marked as * `expired' and removed from the cache upon return. * * @param cacheKey the key to look up the cache * @param control the Control to be used for the expiration control * @return the cached bundle, or null if the bundle is not found in the * cache or its parent has expired. bundle.expire is true * upon return if the bundle in the cache has expired. */ private static final ResourceBundle findBundleInCache(CacheKey cacheKey, Control control) { BundleReference bundleRef = cacheList.get(cacheKey); if (bundleRef == null) { return null; } ResourceBundle bundle = bundleRef.get(); if (bundle == null) { return null; } ResourceBundle p = bundle.parent; assert p != NONEXISTENT_BUNDLE; // If the parent has expired, then this one must also expire. We // check only the immediate parent because the actual loading is // done from the root (base) to leaf (child) and the purpose of // checking is to propagate expiration towards the leaf. For // example, if the requested locale is ja_JP_JP and there are // bundles for all of the candidates in the cache, we have a list, // // base <- ja <- ja_JP <- ja_JP_JP // // If ja has expired, then it will reload ja and the list becomes a // tree. // // base <- ja (new) // " <- ja (expired) <- ja_JP <- ja_JP_JP // // When looking up ja_JP in the cache, it finds ja_JP in the cache // which references to the expired ja. Then, ja_JP is marked as // expired and removed from the cache. This will be propagated to // ja_JP_JP. // // Now, it's possible, for example, that while loading new ja_JP, // someone else has started loading the same bundle and finds the // base bundle has expired. Then, what we get from the first // getBundle call includes the expired base bundle. However, if // someone else didn't start its loading, we wouldn't know if the // base bundle has expired at the end of the loading process. The // expiration control doesn't guarantee that the returned bundle and // its parents haven't expired. // // We could check the entire parent chain to see if there's any in // the chain that has expired. But this process may never end. An // extreme case would be that getTimeToLive returns 0 and // needsReload always returns true. if (p != null && p.expired) { assert bundle != NONEXISTENT_BUNDLE; bundle.expired = true; bundle.cacheKey = null; cacheList.remove(cacheKey, bundleRef); bundle = null; } else { CacheKey key = bundleRef.getCacheKey(); long expirationTime = key.expirationTime; if (!bundle.expired && expirationTime >= 0 && expirationTime <= System.currentTimeMillis()) { // its TTL period has expired. if (bundle != NONEXISTENT_BUNDLE) { // Synchronize here to call needsReload to avoid // redundant concurrent calls for the same bundle. synchronized (bundle) { expirationTime = key.expirationTime; if (!bundle.expired && expirationTime >= 0 && expirationTime <= System.currentTimeMillis()) { try { bundle.expired = control.needsReload(key.getName(), key.getLocale(), key.getFormat(), key.getLoader(), bundle, key.loadTime); } catch (Exception e) { cacheKey.setCause(e); } if (bundle.expired) { // If the bundle needs to be reloaded, then // remove the bundle from the cache, but // return the bundle with the expired flag // on. bundle.cacheKey = null; cacheList.remove(cacheKey, bundleRef); } else { // Update the expiration control info. and reuse // the same bundle instance setExpirationTime(key, control); } } } } else { // We just remove NONEXISTENT_BUNDLE from the cache. cacheList.remove(cacheKey, bundleRef); bundle = null; } } } return bundle; } /** * Put a new bundle in the cache. * * @param cacheKey the key for the resource bundle * @param bundle the resource bundle to be put in the cache * @return the ResourceBundle for the cacheKey; if someone has put * the bundle before this call, the one found in the cache is * returned. */ private static final ResourceBundle putBundleInCache(CacheKey cacheKey, ResourceBundle bundle, Control control) { setExpirationTime(cacheKey, control); if (cacheKey.expirationTime != Control.TTL_DONT_CACHE) { CacheKey key = (CacheKey) cacheKey.clone(); BundleReference bundleRef = new BundleReference(bundle, referenceQueue, key); bundle.cacheKey = key; // Put the bundle in the cache if it's not been in the cache. BundleReference result = cacheList.putIfAbsent(key, bundleRef); // If someone else has put the same bundle in the cache before // us and it has not expired, we should use the one in the cache. if (result != null) { ResourceBundle rb = result.get(); if (rb != null && !rb.expired) { // Clear the back link to the cache key bundle.cacheKey = null; bundle = rb; // Clear the reference in the BundleReference so that // it won't be enqueued. bundleRef.clear(); } else { // Replace the invalid (garbage collected or expired) // instance with the valid one. cacheList.put(key, bundleRef); } } } return bundle; } private static final void setExpirationTime(CacheKey cacheKey, Control control) { long ttl = control.getTimeToLive(cacheKey.getName(), cacheKey.getLocale()); if (ttl >= 0) { // If any expiration time is specified, set the time to be // expired in the cache. long now = System.currentTimeMillis(); cacheKey.loadTime = now; cacheKey.expirationTime = now + ttl; } else if (ttl >= Control.TTL_NO_EXPIRATION_CONTROL) { cacheKey.expirationTime = ttl; } else { throw new IllegalArgumentException("Invalid Control: TTL=" + ttl); } } /** * Removes all resource bundles from the cache that have been loaded * using the caller's class loader. * * @since 1.6 * @see ResourceBundle.Control#getTimeToLive(String,Locale) */ public static final void clearCache() { clearCache(getLoader()); } /** * Removes all resource bundles from the cache that have been loaded * using the given class loader. * * @param loader the class loader * @exception NullPointerException if loader is null * @since 1.6 * @see ResourceBundle.Control#getTimeToLive(String,Locale) */ public static final void clearCache(ClassLoader loader) { if (loader == null) { throw new NullPointerException(); } Set set = cacheList.keySet(); for (CacheKey key : set) { if (key.getLoader() == loader) { set.remove(key); } } } /** * Gets an object for the given key from this resource bundle. * Returns null if this resource bundle does not contain an * object for the given key. * * @param key the key for the desired object * @exception NullPointerException if key is null * @return the object for the given key, or null */ protected abstract Object handleGetObject(String key); /** * Returns an enumeration of the keys. * * @return an Enumeration of the keys contained in * this ResourceBundle and its parent bundles. */ public abstract Enumeration getKeys(); /** * Determines whether the given key is contained in * this ResourceBundle or its parent bundles. * * @param key * the resource key * @return true if the given key is * contained in this ResourceBundle or its * parent bundles; false otherwise. * @exception NullPointerException * if key is null * @since 1.6 */ public boolean containsKey(String key) { if (key == null) { throw new NullPointerException(); } for (ResourceBundle rb = this; rb != null; rb = rb.parent) { if (rb.handleKeySet().contains(key)) { return true; } } return false; } /** * Returns a Set of all keys contained in this * ResourceBundle and its parent bundles. * * @return a Set of all keys contained in this * ResourceBundle and its parent bundles. * @since 1.6 */ public Set keySet() { Set keys = new HashSet(); for (ResourceBundle rb = this; rb != null; rb = rb.parent) { keys.addAll(rb.handleKeySet()); } return keys; } /** * Returns a Set of the keys contained only * in this ResourceBundle. * *

The default implementation returns a Set of the * keys returned by the {@link #getKeys() getKeys} method except * for the ones for which the {@link #handleGetObject(String) * handleGetObject} method returns null. Once the * Set has been created, the value is kept in this * ResourceBundle in order to avoid producing the * same Set in the next calls. Override this method * in subclass implementations for faster handling. * * @return a Set of the keys contained only in this * ResourceBundle * @since 1.6 */ protected Set handleKeySet() { if (keySet == null) { synchronized (this) { if (keySet == null) { Set keys = new HashSet(); Enumeration enumKeys = getKeys(); while (enumKeys.hasMoreElements()) { String key = enumKeys.nextElement(); if (handleGetObject(key) != null) { keys.add(key); } } keySet = keys; } } } return keySet; } /** * ResourceBundle.Control defines a set of callback methods * that are invoked by the {@link ResourceBundle#getBundle(String, * Locale, ClassLoader, Control) ResourceBundle.getBundle} factory * methods during the bundle loading process. In other words, a * ResourceBundle.Control collaborates with the factory * methods for loading resource bundles. The default implementation of * the callback methods provides the information necessary for the * factory methods to perform the default behavior. * *

In addition to the callback methods, the {@link * #toBundleName(String, Locale) toBundleName} and {@link * #toResourceName(String, String) toResourceName} methods are defined * primarily for convenience in implementing the callback * methods. However, the toBundleName method could be * overridden to provide different conventions in the organization and * packaging of localized resources. The toResourceName * method is final to avoid use of wrong resource and class * name separators. * *

Two factory methods, {@link #getControl(List)} and {@link * #getNoFallbackControl(List)}, provide * ResourceBundle.Control instances that implement common * variations of the default bundle loading process. * *

The formats returned by the {@link Control#getFormats(String) * getFormats} method and candidate locales returned by the {@link * ResourceBundle.Control#getCandidateLocales(String, Locale) * getCandidateLocales} method must be consistent in all * ResourceBundle.getBundle invocations for the same base * bundle. Otherwise, the ResourceBundle.getBundle methods * may return unintended bundles. For example, if only * "java.class" is returned by the getFormats * method for the first call to ResourceBundle.getBundle * and only "java.properties" for the second call, then the * second call will return the class-based one that has been cached * during the first call. * *

A ResourceBundle.Control instance must be thread-safe * if it's simultaneously used by multiple threads. * ResourceBundle.getBundle does not synchronize to call * the ResourceBundle.Control methods. The default * implementations of the methods are thread-safe. * *

Applications can specify ResourceBundle.Control * instances returned by the getControl factory methods or * created from a subclass of ResourceBundle.Control to * customize the bundle loading process. The following are examples of * changing the default bundle loading process. * *

Example 1 * *

The following code lets ResourceBundle.getBundle look * up only properties-based resources. * *

 * import java.util.*; * import static java.util.ResourceBundle.Control.*; * ... * ResourceBundle bundle = * ResourceBundle.getBundle("MyResources", new Locale("fr", "CH"), * ResourceBundle.Control.getControl(FORMAT_PROPERTIES)); *

* * Given the resource bundles in the example in * the ResourceBundle.getBundle description, this * ResourceBundle.getBundle call loads * MyResources_fr_CH.properties whose parent is * MyResources_fr.properties whose parent is * MyResources.properties. (MyResources_fr_CH.properties * is not hidden, but MyResources_fr_CH.class is.) * *

Example 2 * *

The following is an example of loading XML-based bundles * using {@link Properties#loadFromXML(java.io.InputStream) * Properties.loadFromXML}. * *

 * ResourceBundle rb = ResourceBundle.getBundle("Messages", * new ResourceBundle.Control() { * public List getFormats(String baseName) { * if (baseName == null) * throw new NullPointerException(); * return Arrays.asList("xml"); * } * public ResourceBundle newBundle(String baseName, * Locale locale, * String format, * ClassLoader loader, * boolean reload) * throws IllegalAccessException, * InstantiationException, * IOException { * if (baseName == null || locale == null * || format == null || loader == null) * throw new NullPointerException(); * ResourceBundle bundle = null; * if (format.equals("xml")) { * String bundleName = toBundleName(baseName, locale); * String resourceName = toResourceName(bundleName, format); * InputStream stream = null; * if (reload) { * URL url = loader.getResource(resourceName); * if (url != null) { * URLConnection connection = url.openConnection(); * if (connection != null) { * // Disable caches to get fresh data for * // reloading. * connection.setUseCaches(false); * stream = connection.getInputStream(); * } * } * } else { * stream = loader.getResourceAsStream(resourceName); * } * if (stream != null) { * BufferedInputStream bis = new BufferedInputStream(stream); * bundle = new XMLResourceBundle(bis); * bis.close(); * } * } * return bundle; * } * }); * * ... * * private static class XMLResourceBundle extends ResourceBundle { * private Properties props; * XMLResourceBundle(InputStream stream) throws IOException { * props = new Properties(); * props.loadFromXML(stream); * } * protected Object handleGetObject(String key) { * return props.getProperty(key); * } * public Enumeration getKeys() { * ... * } * } *

* * @since 1.6 */ public static class Control { /** * The default format List, which contains the strings * "java.class" and "java.properties", in * this order. This List is {@linkplain * Collections#unmodifiableList(List) unmodifiable}. * * @see #getFormats(String) */ public static final List FORMAT_DEFAULT = Collections.unmodifiableList(Arrays.asList("java.class", "java.properties")); /** * The class-only format List containing * "java.class". This List is {@linkplain * Collections#unmodifiableList(List) unmodifiable}. * * @see #getFormats(String) */ public static final List FORMAT_CLASS = Collections.unmodifiableList(Arrays.asList("java.class")); /** * The properties-only format List containing * "java.properties". This List is * {@linkplain Collections#unmodifiableList(List) unmodifiable}. * * @see #getFormats(String) */ public static final List FORMAT_PROPERTIES = Collections.unmodifiableList(Arrays.asList("java.properties")); /** * The time-to-live constant for not caching loaded resource bundle * instances. * * @see #getTimeToLive(String, Locale) */ public static final long TTL_DONT_CACHE = -1; /** * The time-to-live constant for disabling the expiration control * for loaded resource bundle instances in the cache. * * @see #getTimeToLive(String, Locale) */ public static final long TTL_NO_EXPIRATION_CONTROL = -2; private static final Control INSTANCE = new Control(); /** * Sole constructor. (For invocation by subclass constructors, * typically implicit.) */ protected Control() { } /** * Returns a ResourceBundle.Control in which the {@link * #getFormats(String) getFormats} method returns the specified * formats. The formats must be equal to * one of {@link Control#FORMAT_PROPERTIES}, {@link * Control#FORMAT_CLASS} or {@link * Control#FORMAT_DEFAULT}. ResourceBundle.Control * instances returned by this method are singletons and thread-safe. * *

Specifying {@link Control#FORMAT_DEFAULT} is equivalent to * instantiating the ResourceBundle.Control class, * except that this method returns a singleton. * * @param formats * the formats to be returned by the * ResourceBundle.Control.getFormats method * @return a ResourceBundle.Control supporting the * specified formats * @exception NullPointerException * if formats is null * @exception IllegalArgumentException * if formats is unknown */ public static final Control getControl(List formats) { if (formats.equals(Control.FORMAT_PROPERTIES)) { return SingleFormatControl.PROPERTIES_ONLY; } if (formats.equals(Control.FORMAT_CLASS)) { return SingleFormatControl.CLASS_ONLY; } if (formats.equals(Control.FORMAT_DEFAULT)) { return Control.INSTANCE; } throw new IllegalArgumentException(); } /** * Returns a ResourceBundle.Control in which the {@link * #getFormats(String) getFormats} method returns the specified * formats and the {@link * Control#getFallbackLocale(String, Locale) getFallbackLocale} * method returns null. The formats must * be equal to one of {@link Control#FORMAT_PROPERTIES}, {@link * Control#FORMAT_CLASS} or {@link Control#FORMAT_DEFAULT}. * ResourceBundle.Control instances returned by this * method are singletons and thread-safe. * * @param formats * the formats to be returned by the * ResourceBundle.Control.getFormats method * @return a ResourceBundle.Control supporting the * specified formats with no fallback * Locale support * @exception NullPointerException * if formats is null * @exception IllegalArgumentException * if formats is unknown */ public static final Control getNoFallbackControl(List formats) { if (formats.equals(Control.FORMAT_DEFAULT)) { return NoFallbackControl.NO_FALLBACK; } if (formats.equals(Control.FORMAT_PROPERTIES)) { return NoFallbackControl.PROPERTIES_ONLY_NO_FALLBACK; } if (formats.equals(Control.FORMAT_CLASS)) { return NoFallbackControl.CLASS_ONLY_NO_FALLBACK; } throw new IllegalArgumentException(); } /** * Returns a List of Strings containing * formats to be used to load resource bundles for the given * baseName. The ResourceBundle.getBundle * factory method tries to load resource bundles with formats in the * order specified by the list. The list returned by this method * must have at least one String. The predefined * formats are "java.class" for class-based resource * bundles and "java.properties" for {@linkplain * PropertyResourceBundle properties-based} ones. Strings starting * with "java." are reserved for future extensions and * must not be used by application-defined formats. * *

It is not a requirement to return an immutable (unmodifiable) * List. However, the returned List must * not be mutated after it has been returned by * getFormats. * *

The default implementation returns {@link #FORMAT_DEFAULT} so * that the ResourceBundle.getBundle factory method * looks up first class-based resource bundles, then * properties-based ones. * * @param baseName * the base name of the resource bundle, a fully qualified class * name * @return a List of Strings containing * formats for loading resource bundles. * @exception NullPointerException * if baseName is null * @see #FORMAT_DEFAULT * @see #FORMAT_CLASS * @see #FORMAT_PROPERTIES */ public List getFormats(String baseName) { if (baseName == null) { throw new NullPointerException(); } return FORMAT_DEFAULT; } /** * Returns a List of Locales as candidate * locales for baseName and locale. This * method is called by the ResourceBundle.getBundle * factory method each time the factory method tries finding a * resource bundle for a target Locale. * *

The sequence of the candidate locales also corresponds to the * runtime resource lookup path (also known as the parent * chain), if the corresponding resource bundles for the * candidate locales exist and their parents are not defined by * loaded resource bundles themselves. The last element of the list * must be a {@linkplain Locale#ROOT root locale} if it is desired to * have the base bundle as the terminal of the parent chain. * *

If the given locale is equal to Locale.ROOT (the * root locale), a List containing only the root * Locale must be returned. In this case, the * ResourceBundle.getBundle factory method loads only * the base bundle as the resulting resource bundle. * *

It is not a requirement to return an immutable * (unmodifiable) List. However, the returned * List must not be mutated after it has been * returned by getCandidateLocales. * *

The default implementation returns a List containing * Locales in the following sequence: *

 * Locale(language, country, variant) * Locale(language, country) * Locale(language) * Locale.ROOT *

* where language, country and * variant are the language, country and variant values * of the given locale, respectively. Locales where the * final component values are empty strings are omitted. * *

The default implementation uses an {@link ArrayList} that * overriding implementations may modify before returning it to the * caller. However, a subclass must not modify it after it has * been returned by getCandidateLocales. * *

For example, if the given baseName is "Messages" * and the given locale is * Locale("ja", "", "XX"), then a * List of Locales: *

 * Locale("ja", "", "XX") * Locale("ja") * Locale.ROOT *

* is returned. And if the resource bundles for the "ja" and * "" Locales are found, then the runtime resource * lookup path (parent chain) is: *

 * Messages_ja -> Messages *

* * @param baseName * the base name of the resource bundle, a fully * qualified class name * @param locale * the locale for which a resource bundle is desired * @return a List of candidate * Locales for the given locale * @exception NullPointerException * if baseName or locale is * null */ public List getCandidateLocales(String baseName, Locale locale) { if (baseName == null) { throw new NullPointerException(); } String language = locale.getLanguage(); String country = locale.getCountry(); String variant = locale.getVariant(); List locales = new ArrayList(4); if (variant.length() > 0) { locales.add(locale); } if (country.length() > 0) { locales.add((locales.size() == 0) ? locale : Locale.getInstance(language, country, "")); } if (language.length() > 0) { locales.add((locales.size() == 0) ? locale : Locale.getInstance(language, "", "")); } locales.add(Locale.ROOT); return locales; } /** * Returns a Locale to be used as a fallback locale for * further resource bundle searches by the * ResourceBundle.getBundle factory method. This method * is called from the factory method every time when no resulting * resource bundle has been found for baseName and * locale, where locale is either the parameter for * ResourceBundle.getBundle or the previous fallback * locale returned by this method. * *

The method returns null if no further fallback * search is desired. * *

The default implementation returns the {@linkplain * Locale#getDefault() default Locale} if the given * locale isn't the default one. Otherwise, * null is returned. * * @param baseName * the base name of the resource bundle, a fully * qualified class name for which * ResourceBundle.getBundle has been * unable to find any resource bundles (except for the * base bundle) * @param locale * the Locale for which * ResourceBundle.getBundle has been * unable to find any resource bundles (except for the * base bundle) * @return a Locale for the fallback search, * or null if no further fallback search * is desired. * @exception NullPointerException * if baseName or locale * is null */ public Locale getFallbackLocale(String baseName, Locale locale) { if (baseName == null) { throw new NullPointerException(); } Locale defaultLocale = Locale.getDefault(); return locale.equals(defaultLocale) ? null : defaultLocale; } /** * Instantiates a resource bundle for the given bundle name of the * given format and locale, using the given class loader if * necessary. This method returns null if there is no * resource bundle available for the given parameters. If a resource * bundle can't be instantiated due to an unexpected error, the * error must be reported by throwing an Error or * Exception rather than simply returning * null. * *

If the reload flag is true, it * indicates that this method is being called because the previously * loaded resource bundle has expired. * *

The default implementation instantiates a * ResourceBundle as follows. * *

The bundle name is obtained by calling {@link * #toBundleName(String, Locale) toBundleName(baseName, * locale)}.
If format is "java.class", the * {@link Class} specified by the bundle name is loaded by calling * {@link ClassLoader#loadClass(String)}. Then, a * ResourceBundle is instantiated by calling {@link * Class#newInstance()}. Note that the reload flag is * ignored for loading class-based resource bundles in this default * implementation.
If format is "java.properties", * {@link #toResourceName(String, String) toResourceName(bundlename, * "properties")} is called to get the resource name. * If reload is true, {@link * ClassLoader#getResource(String) load.getResource} is called * to get a {@link URL} for creating a {@link * URLConnection}. This URLConnection is used to * {@linkplain URLConnection#setUseCaches(boolean) disable the * caches} of the underlying resource loading layers, * and to {@linkplain URLConnection#getInputStream() get an * InputStream}. * Otherwise, {@link ClassLoader#getResourceAsStream(String) * loader.getResourceAsStream} is called to get an {@link * InputStream}. Then, a {@link * PropertyResourceBundle} is constructed with the * InputStream.
If format is neither "java.class" * nor "java.properties", an * IllegalArgumentException is thrown.

* * @param baseName * the base bundle name of the resource bundle, a fully * qualified class name * @param locale * the locale for which the resource bundle should be * instantiated * @param format * the resource bundle format to be loaded * @param loader * the ClassLoader to use to load the bundle * @param reload * the flag to indicate bundle reloading; true * if reloading an expired resource bundle, * false otherwise * @return the resource bundle instance, * or null if none could be found. * @exception NullPointerException * if bundleName, locale, * format, or loader is * null, or if null is returned by * {@link #toBundleName(String, Locale) toBundleName} * @exception IllegalArgumentException * if format is unknown, or if the resource * found for the given parameters contains malformed data. * @exception ClassCastException * if the loaded class cannot be cast to ResourceBundle * @exception IllegalAccessException * if the class or its nullary constructor is not * accessible. * @exception InstantiationException * if the instantiation of a class fails for some other * reason. * @exception ExceptionInInitializerError * if the initialization provoked by this method fails. * @exception SecurityException * If a security manager is present and creation of new * instances is denied. See {@link Class#newInstance()} * for details. * @exception IOException * if an error occurred when reading resources using * any I/O operations */ public ResourceBundle newBundle(String baseName, Locale locale, String format, ClassLoader loader, boolean reload) throws IllegalAccessException, InstantiationException, IOException { String bundleName = toBundleName(baseName, locale); ResourceBundle bundle = null; if (format.equals("java.class")) { try { Class bundleClass = (Class)loader.loadClass(bundleName); // If the class isn't a ResourceBundle subclass, throw a // ClassCastException. if (ResourceBundle.class.isAssignableFrom(bundleClass)) { bundle = bundleClass.newInstance(); } else { throw new ClassCastException(bundleClass.getName() + " cannot be cast to ResourceBundle"); } } catch (ClassNotFoundException e) { } } else if (format.equals("java.properties")) { final String resourceName = toResourceName(bundleName, "properties"); final ClassLoader classLoader = loader; final boolean reloadFlag = reload; InputStream stream = null; try { stream = AccessController.doPrivileged( new PrivilegedExceptionAction() { public InputStream run() throws IOException { InputStream is = null; if (reloadFlag) { URL url = classLoader.getResource(resourceName); if (url != null) { URLConnection connection = url.openConnection(); if (connection != null) { // Disable caches to get fresh data for // reloading. connection.setUseCaches(false); is = connection.getInputStream(); } } } else { is = classLoader.getResourceAsStream(resourceName); } return is; } }); } catch (PrivilegedActionException e) { throw (IOException) e.getException(); } if (stream != null) { try { bundle = new PropertyResourceBundle(stream); } finally { stream.close(); } } } else { throw new IllegalArgumentException("unknown format: " + format); } return bundle; } /** * Returns the time-to-live (TTL) value for resource bundles that * are loaded under this * ResourceBundle.Control. Positive time-to-live values * specify the number of milliseconds a bundle can remain in the * cache without being validated against the source data from which * it was constructed. The value 0 indicates that a bundle must be * validated each time it is retrieved from the cache. {@link * #TTL_DONT_CACHE} specifies that loaded resource bundles are not * put in the cache. {@link #TTL_NO_EXPIRATION_CONTROL} specifies * that loaded resource bundles are put in the cache with no * expiration control. * *

The expiration affects only the bundle loading process by the * ResourceBundle.getBundle factory method. That is, * if the factory method finds a resource bundle in the cache that * has expired, the factory method calls the {@link * #needsReload(String, Locale, String, ClassLoader, ResourceBundle, * long) needsReload} method to determine whether the resource * bundle needs to be reloaded. If needsReload returns * true, the cached resource bundle instance is removed * from the cache. Otherwise, the instance stays in the cache, * updated with the new TTL value returned by this method. * *

All cached resource bundles are subject to removal from the * cache due to memory constraints of the runtime environment. * Returning a large positive value doesn't mean to lock loaded * resource bundles in the cache. * *

The default implementation returns {@link #TTL_NO_EXPIRATION_CONTROL}. * * @param baseName * the base name of the resource bundle for which the * expiration value is specified. * @param locale * the locale of the resource bundle for which the * expiration value is specified. * @return the time (0 or a positive millisecond offset from the * cached time) to get loaded bundles expired in the cache, * {@link #TTL_NO_EXPIRATION_CONTROL} to disable the * expiration control, or {@link #TTL_DONT_CACHE} to disable * caching. * @exception NullPointerException * if baseName or locale is * null */ public long getTimeToLive(String baseName, Locale locale) { if (baseName == null || locale == null) { throw new NullPointerException(); } return TTL_NO_EXPIRATION_CONTROL; } /** * Determines if the expired bundle in the cache needs * to be reloaded based on the loading time given by * loadTime or some other criteria. The method returns * true if reloading is required; false * otherwise. loadTime is a millisecond offset since * the Calendar * Epoch. * * The calling ResourceBundle.getBundle factory method * calls this method on the ResourceBundle.Control * instance used for its current invocation, not on the instance * used in the invocation that originally loaded the resource * bundle. * *

The default implementation compares loadTime and * the last modified time of the source data of the resource * bundle. If it's determined that the source data has been modified * since loadTime, true is * returned. Otherwise, false is returned. This * implementation assumes that the given format is the * same string as its file suffix if it's not one of the default * formats, "java.class" or * "java.properties". * * @param baseName * the base bundle name of the resource bundle, a * fully qualified class name * @param locale * the locale for which the resource bundle * should be instantiated * @param format * the resource bundle format to be loaded * @param loader * the ClassLoader to use to load the bundle * @param bundle * the resource bundle instance that has been expired * in the cache * @param loadTime * the time when bundle was loaded and put * in the cache * @return true if the expired bundle needs to be * reloaded; false otherwise. * @exception NullPointerException * if baseName, locale, * format, loader, or * bundle is null */ public boolean needsReload(String baseName, Locale locale, String format, ClassLoader loader, ResourceBundle bundle, long loadTime) { if (bundle == null) { throw new NullPointerException(); } if (format.equals("java.class") || format.equals("java.properties")) { format = format.substring(5); } boolean result = false; try { String resourceName = toResourceName(toBundleName(baseName, locale), format); URL url = loader.getResource(resourceName); if (url != null) { long lastModified = 0; URLConnection connection = url.openConnection(); if (connection != null) { // disable caches to get the correct data connection.setUseCaches(false); if (connection instanceof JarURLConnection) { JarEntry ent = ((JarURLConnection)connection).getJarEntry(); if (ent != null) { lastModified = ent.getTime(); if (lastModified == -1) { lastModified = 0; } } } else { lastModified = connection.getLastModified(); } } result = lastModified >= loadTime; } } catch (NullPointerException npe) { throw npe; } catch (Exception e) { // ignore other exceptions } return result; } /** * Converts the given baseName and locale * to the bundle name. This method is called from the default * implementation of the {@link #newBundle(String, Locale, String, * ClassLoader, boolean) newBundle} and {@link #needsReload(String, * Locale, String, ClassLoader, ResourceBundle, long) needsReload} * methods. * *

This implementation returns the following value: *

 * baseName + "_" + language + "_" + country + "_" + variant *

* where language, country and * variant are the language, country and variant values * of locale, respectively. Final component values that * are empty Strings are omitted along with the preceding '_'. If * all of the values are empty strings, then baseName * is returned. * *

For example, if baseName is * "baseName" and locale is * Locale("ja", "", "XX"), then * "baseName_ja_ _XX" is returned. If the given * locale is Locale("en"), then * "baseName_en" is returned. * *

Overriding this method allows applications to use different * conventions in the organization and packaging of localized * resources. * * @param baseName * the base name of the resource bundle, a fully * qualified class name * @param locale * the locale for which a resource bundle should be * loaded * @return the bundle name for the resource bundle * @exception NullPointerException * if baseName or locale * is null */ public String toBundleName(String baseName, Locale locale) { if (locale == Locale.ROOT) { return baseName; } String language = locale.getLanguage(); String country = locale.getCountry(); String variant = locale.getVariant(); if (language == "" && country == "" && variant == "") { return baseName; } StringBuilder sb = new StringBuilder(baseName); sb.append('_'); if (variant != "") { sb.append(language).append('_').append(country).append('_').append(variant); } else if (country != "") { sb.append(language).append('_').append(country); } else { sb.append(language); } return sb.toString(); } /** * Converts the given bundleName to the form required * by the {@link ClassLoader#getResource ClassLoader.getResource} * method by replacing all occurrences of '.' in * bundleName with '/' and appending a * '.' and the given file suffix. For * example, if bundleName is * "foo.bar.MyResources_ja_JP" and suffix * is "properties", then * "foo/bar/MyResources_ja_JP.properties" is returned. * * @param bundleName * the bundle name * @param suffix * the file type suffix * @return the converted resource name * @exception NullPointerException * if bundleName or suffix * is null */ public final String toResourceName(String bundleName, String suffix) { StringBuilder sb = new StringBuilder(bundleName.length() + 1 + suffix.length()); sb.append(bundleName.replace('.', '/')).append('.').append(suffix); return sb.toString(); } } private static class SingleFormatControl extends Control { private static final Control PROPERTIES_ONLY = new SingleFormatControl(FORMAT_PROPERTIES); private static final Control CLASS_ONLY = new SingleFormatControl(FORMAT_CLASS); private final List formats; protected SingleFormatControl(List formats) { this.formats = formats; } public List getFormats(String baseName) { if (baseName == null) { throw new NullPointerException(); } return formats; } } private static final class NoFallbackControl extends SingleFormatControl { private static final Control NO_FALLBACK = new NoFallbackControl(FORMAT_DEFAULT); private static final Control PROPERTIES_ONLY_NO_FALLBACK = new NoFallbackControl(FORMAT_PROPERTIES); private static final Control CLASS_ONLY_NO_FALLBACK = new NoFallbackControl(FORMAT_CLASS); protected NoFallbackControl(List formats) { super(formats); } public Locale getFallbackLocale(String baseName, Locale locale) { if (baseName == null || locale == null) { throw new NullPointerException(); } return null; } } }

Locale *	format *
Locale("de", "DE") *	java.class *
Locale("de", "DE")	java.properties *
Locale("de")	java.class
Locale("de")	java.properties
Locale("") *	java.class
Locale("")	java.properties

ResourceBundle 类介绍 （二）源码分析

ResourceBundle.Control

Cache Management

Example

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ResourceBundle 类介绍（二）源码分析