资源管理StringManager

package org.apache.catalina.util;

import java.text.MessageFormat;
import java.util.Hashtable;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import java.net.URLClassLoader;

/**
管理字符串，到包级，很好的处理国际化等问题
 */

public class StringManager {

    /**
     * The ResourceBundle for this StringManager.
     */

    private ResourceBundle bundle;
    
    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog( StringManager.class );
    
    /**
     * Creates a new StringManager for a given package. This is a
     * private method and all access to it is arbitrated by the
     * static getManager method call so that only one StringManager
     * per package will be created.
     *
     * @param packageName Name of package to create StringManager for.
     */

    private StringManager(String packageName) {
        String bundleName = packageName + ".LocalStrings";
        try {
            bundle = ResourceBundle.getBundle(bundleName);
            return;
        } catch( MissingResourceException ex ) {
            // Try from the current loader ( that's the case for trusted apps )
            ClassLoader cl=Thread.currentThread().getContextClassLoader();
            if( cl != null ) {
                try {
                    bundle=ResourceBundle.getBundle(bundleName, Locale.getDefault(), cl);
                    return;
                } catch(MissingResourceException ex2) {
                }
            }
            if( cl==null )
                cl=this.getClass().getClassLoader();

            if (log.isDebugEnabled())
                log.debug("Can't find resource " + bundleName +
                    " " + cl);
            if( cl instanceof URLClassLoader ) {
                if (log.isDebugEnabled()) 
                    log.debug( ((URLClassLoader)cl).getURLs());
            }
        }
    }

    /**
     * Get a string from the underlying resource bundle.
     *
     * @param key The resource name
     */
    public String getString(String key) {
        return MessageFormat.format(getStringInternal(key), (Object [])null);
    }


    protected String getStringInternal(String key) {
        if (key == null) {
            String msg = "key is null";

            throw new NullPointerException(msg);
        }

        String str = null;

        if( bundle==null )
            return key;
        try {
            str = bundle.getString(key);
        } catch (MissingResourceException mre) {
            str = "Cannot find message associated with key '" + key + "'";
        }

        return str;
    }

    /**
     * Get a string from the underlying resource bundle and format
     * it with the given set of arguments.
     *
     * @param key The resource name
     * @param args Formatting directives
     */

    public String getString(String key, Object[] args) {
        String iString = null;
        String value = getStringInternal(key);

        // this check for the runtime exception is some pre 1.1.6
        // VM's don't do an automatic toString() on the passed in
        // objects and barf out

        try {
            // ensure the arguments are not null so pre 1.2 VM's don't barf
            Object nonNullArgs[] = args;
            for (int i=0; i<args.length; i++) {
                if (args[i] == null) {
                    if (nonNullArgs==args) nonNullArgs=(Object[])args.clone();
                    nonNullArgs[i] = "null";
                }
            }

            iString = MessageFormat.format(value, nonNullArgs);
        } catch (IllegalArgumentException iae) {
            StringBuffer buf = new StringBuffer();
            buf.append(value);
            for (int i = 0; i < args.length; i++) {
                buf.append(" arg[" + i + "]=" + args[i]);
            }
            iString = buf.toString();
        }
        return iString;
    }

    /**
     * Get a string from the underlying resource bundle and format it
     * with the given object argument. This argument can of course be
     * a String object.
     *
     * @param key The resource name
     * @param arg Formatting directive
     */

    public String getString(String key, Object arg) {
        Object[] args = new Object[] {arg};
        return getString(key, args);
    }

    /**
     * Get a string from the underlying resource bundle and format it
     * with the given object arguments. These arguments can of course
     * be String objects.
     *
     * @param key The resource name
     * @param arg1 Formatting directive
     * @param arg2 Formatting directive
     */

    public String getString(String key, Object arg1, Object arg2) {
        Object[] args = new Object[] {arg1, arg2};
        return getString(key, args);
    }

    /**
     * Get a string from the underlying resource bundle and format it
     * with the given object arguments. These arguments can of course
     * be String objects.
     *
     * @param key The resource name
     * @param arg1 Formatting directive
     * @param arg2 Formatting directive
     * @param arg3 Formatting directive
     */

    public String getString(String key, Object arg1, Object arg2,
                            Object arg3) {
        Object[] args = new Object[] {arg1, arg2, arg3};
        return getString(key, args);
    }

    /**
     * Get a string from the underlying resource bundle and format it
     * with the given object arguments. These arguments can of course
     * be String objects.
     *
     * @param key The resource name
     * @param arg1 Formatting directive
     * @param arg2 Formatting directive
     * @param arg3 Formatting directive
     * @param arg4 Formatting directive
     */

    public String getString(String key, Object arg1, Object arg2,
                            Object arg3, Object arg4) {
        Object[] args = new Object[] {arg1, arg2, arg3, arg4};
        return getString(key, args);
    }
    // --------------------------------------------------------------
    // STATIC SUPPORT METHODS
    // --------------------------------------------------------------

    private static Hashtable managers = new Hashtable();

    /**
     * Get the StringManager for a particular package. If a manager for
     * a package already exists, it will be reused, else a new
     * StringManager will be created and returned.
     *
     * @param packageName The package name
     */

    public synchronized static StringManager getManager(String packageName) {
        StringManager mgr = (StringManager)managers.get(packageName);

        if (mgr == null) {
            mgr = new StringManager(packageName);
            managers.put(packageName, mgr);
        }
        return mgr;
    }
}