Spring的资源抽象Resource2实体类

一、文件系统资源 FileSystemResource

　　文件系统资源 FileSystemResource，资源以文件系统路径的方式表示 ，唯一一个实现了WritableResource接口的类。 这个类由2个不可变的属性 file 和 path ，本质上就是一个java.io.File 的包装。 这个类的 equals() 和 hashcode() 都通过属性 path 来操作。

public class FileSystemResource extends AbstractResource implements WritableResource {

    private final File file;   //  不可变属性

    private final String path; //  不可变属性

    public FileSystemResource(File file) { //  简单的构造方法，path为file路径格式化后的样子
        Assert.notNull(file, "File must not be null");
        this.file = file;
        this.path = StringUtils.cleanPath(file.getPath());
    }

    public FileSystemResource(String path) {   //简单的构造方法
        Assert.notNull(path, "Path must not be null");
        this.file = new File(path);
        this.path = StringUtils.cleanPath(path);
    }

    public final String getPath() {    //新增的方法，返回资源路径，方法不可重写
        return this.path;
    }

    @Override
    public boolean exists() {  
        return this.file.exists();
    }

    @Override
    public boolean isReadable() {
        return (this.file.canRead() && !this.file.isDirectory());
    }

    public InputStream getInputStream() throws IOException {   //InputStreamSource接口的实现方法
        return new FileInputStream(this.file);
    }

    @Override
    public URL getURL() throws IOException {   //可见这个url是通过uri得到的
        return this.file.toURI().toURL();
    }

    @Override
    public URI getURI() throws IOException {
        return this.file.toURI();
    }

    @Override
    public File getFile() {
        return this.file;
    }

    @Override
    public long contentLength() throws IOException {   
        return this.file.length();
    }

    @Override
    public Resource createRelative(String relativePath) {
        String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
        return new FileSystemResource(pathToUse);
    }

    @Override
    public String getFilename() {
        return this.file.getName();
    }
    
    public String getDescription() {   //  资源描述，直接用绝对路径来构造
        return "file [" + this.file.getAbsolutePath() + "]";
    }

    public boolean isWritable() {  //  WritableResource接口的实现方法
        return (this.file.canWrite() && !this.file.isDirectory());
    }

    public OutputStream getOutputStream() throws IOException {
        return new FileOutputStream(this.file);
    }

    @Override
    public boolean equals(Object obj) {    //通过path来比较
        return (obj == this ||
            (obj instanceof FileSystemResource && this.path.equals(((FileSystemResource) obj).path)));
    }

    @Override
    public int hashCode() {    //  文件资源的HashCode就是path的hashCode
        return this.path.hashCode();
    }

}

 

二、常用的 ClassPathResource

ClassPathResource这个资源类表示的是类路径下的资源，资源以相对于类路径的方式表示， 是基于class的 getResourceAsStream(this.path) 或者 this.classLoader.getResourceAsStream(this.path) 。

public class ClassPathResource extends AbstractFileResolvingResource {

    private final String path;

    private ClassLoader classLoader;

    private Class clazz;


    /**
     * Create a new ClassPathResource for ClassLoader usage.
     * A leading slash will be removed, as the ClassLoader
     * resource access methods will not accept it.
     * 
The thread context class loader will be used for
     * loading the resource.
     * @param path the absolute path within the class path
     * @see java.lang.ClassLoader#getResourceAsStream(String)
     * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
     */
    public ClassPathResource(String path) {
        this(path, (ClassLoader) null);
    }

    /**
     * Create a new ClassPathResource for ClassLoader usage.
     * A leading slash will be removed, as the ClassLoader
     * resource access methods will not accept it.
     * @param path the absolute path within the classpath
     * @param classLoader the class loader to load the resource with,
     * or {@code null} for the thread context class loader
     * @see ClassLoader#getResourceAsStream(String)
     */
    public ClassPathResource(String path, ClassLoader classLoader) {
        Assert.notNull(path, "Path must not be null");
        String pathToUse = StringUtils.cleanPath(path);
        if (pathToUse.startsWith("/")) {
            pathToUse = pathToUse.substring(1);
        }
        this.path = pathToUse;
        this.classLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
    }

    /**
     * Create a new ClassPathResource for Class usage.
     * The path can be relative to the given class,
     * or absolute within the classpath via a leading slash.
     * @param path relative or absolute path within the class path
     * @param clazz the class to load resources with
     * @see java.lang.Class#getResourceAsStream
     */
    public ClassPathResource(String path, Class clazz) {
        Assert.notNull(path, "Path must not be null");
        this.path = StringUtils.cleanPath(path);
        this.clazz = clazz;
    }

    /**
     * Create a new ClassPathResource with optional ClassLoader and Class.
     * Only for internal usage.
     * @param path relative or absolute path within the classpath
     * @param classLoader the class loader to load the resource with, if any
     * @param clazz the class to load resources with, if any
     */
    protected ClassPathResource(String path, ClassLoader classLoader, Class clazz) {
        this.path = StringUtils.cleanPath(path);
        this.classLoader = classLoader;
        this.clazz = clazz;
    }

    /**
     * Return the path for this resource (as resource path within the class path).
     */
    public final String getPath() {
        return this.path;
    }

    /**
     * Return the ClassLoader that this resource will be obtained from.
     */
    public final ClassLoader getClassLoader() {
        return (this.classLoader != null ? this.classLoader : this.clazz.getClassLoader());
    }

    /**
     * This implementation checks for the resolution of a resource URL.
     * @see java.lang.ClassLoader#getResource(String)
     * @see java.lang.Class#getResource(String)
     */
    @Override
    public boolean exists() {
        URL url;
        if (this.clazz != null) {
            url = this.clazz.getResource(this.path);
        }
        else {
            url = this.classLoader.getResource(this.path);
        }
        return (url != null);
    }

    /**
     * This implementation opens an InputStream for the given class path resource.
     * @see java.lang.ClassLoader#getResourceAsStream(String)
     * @see java.lang.Class#getResourceAsStream(String)
     */
    public InputStream getInputStream() throws IOException {
        InputStream is;
        if (this.clazz != null) {
            is = this.clazz.getResourceAsStream(this.path);
        }
        else {
            is = this.classLoader.getResourceAsStream(this.path);
        }
        if (is == null) {
            throw new FileNotFoundException(getDescription() + " cannot be opened because it does not exist");
        }
        return is;
    }

    /**
     * This implementation returns a URL for the underlying class path resource.
     * @see java.lang.ClassLoader#getResource(String)
     * @see java.lang.Class#getResource(String)
     */
    @Override
    public URL getURL() throws IOException {
        URL url;
        if (this.clazz != null) {
            url = this.clazz.getResource(this.path);
        }
        else {
            url = this.classLoader.getResource(this.path);
        }
        if (url == null) {
            throw new FileNotFoundException(getDescription() + " cannot be resolved to URL because it does not exist");
        }
        return url;
    }

    /**
     * This implementation creates a ClassPathResource, applying the given path
     * relative to the path of the underlying resource of this descriptor.
     * @see org.springframework.util.StringUtils#applyRelativePath(String, String)
     */
    @Override
    public Resource createRelative(String relativePath) {
        String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
        return new ClassPathResource(pathToUse, this.classLoader, this.clazz);
    }

    /**
     * This implementation returns the name of the file that this class path
     * resource refers to.
     * @see org.springframework.util.StringUtils#getFilename(String)
     */
    @Override
    public String getFilename() {
        return StringUtils.getFilename(this.path);
    }

    /**
     * This implementation returns a description that includes the class path location.
     */
    public String getDescription() {
        StringBuilder builder = new StringBuilder("class path resource [");
        String pathToUse = path;
        if (this.clazz != null && !pathToUse.startsWith("/")) {
            builder.append(ClassUtils.classPackageAsResourcePath(this.clazz));
            builder.append('/');
        }
        if (pathToUse.startsWith("/")) {
            pathToUse = pathToUse.substring(1);
        }
        builder.append(pathToUse);
        builder.append(']');
        return builder.toString();
    }

    /**
     * This implementation compares the underlying class path locations.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj instanceof ClassPathResource) {
            ClassPathResource otherRes = (ClassPathResource) obj;
            return (this.path.equals(otherRes.path) &&
                    ObjectUtils.nullSafeEquals(this.classLoader, otherRes.classLoader) &&
                    ObjectUtils.nullSafeEquals(this.clazz, otherRes.clazz));
        }
        return false;
    }

    /**
     * This implementation returns the hash code of the underlying
     * class path location.
     */
    @Override
    public int hashCode() {
        return this.path.hashCode();
    }

}

 

三、 Url资源——UrlResource

UrlResource这个资源类封装了可以以URL表示的各种资源。这个资源类有3个属性，一个URI、一个URL，以及一个规范化后的URL，用于资源间的比较以及计算HashCode。

public class UrlResource extends AbstractFileResolvingResource {

    /**
     * Original URI, if available; used for URI and File access.
     */
    private final URI uri;

    /**
     * Original URL, used for actual access.
     */
    private final URL url;

    /**
     * Cleaned URL (with normalized path), used for comparisons.
     */
    private final URL cleanedUrl;


    /**
     * Create a new UrlResource based on the given URI object.
     * @param uri a URI
     * @throws MalformedURLException if the given URL path is not valid
     */
    public UrlResource(URI uri) throws MalformedURLException {
        Assert.notNull(uri, "URI must not be null");
        this.uri = uri;
        this.url = uri.toURL();
        this.cleanedUrl = getCleanedUrl(this.url, uri.toString());
    }

    /**
     * Create a new UrlResource based on the given URL object.
     * @param url a URL
     */
    public UrlResource(URL url) {
        Assert.notNull(url, "URL must not be null");
        this.url = url;
        this.cleanedUrl = getCleanedUrl(this.url, url.toString());
        this.uri = null;
    }

    /**
     * Create a new UrlResource based on a URL path.
     * 
Note: The given path needs to be pre-encoded if necessary.
     * @param path a URL path
     * @throws MalformedURLException if the given URL path is not valid
     * @see java.net.URL#URL(String)
     */
    public UrlResource(String path) throws MalformedURLException {
        Assert.notNull(path, "Path must not be null");
        this.uri = null;
        this.url = new URL(path);
        this.cleanedUrl = getCleanedUrl(this.url, path);
    }

    /**
     * Create a new UrlResource based on a URI specification.
     * 
The given parts will automatically get encoded if necessary.
     * @param protocol the URL protocol to use (e.g. "jar" or "file" - without colon);
     * also known as "scheme"
     * @param location the location (e.g. the file path within that protocol);
     * also known as "scheme-specific part"
     * @throws MalformedURLException if the given URL specification is not valid
     * @see java.net.URI#URI(String, String, String)
     */
    public UrlResource(String protocol, String location) throws MalformedURLException  {
        this(protocol, location, null);
    }

    /**
     * Create a new UrlResource based on a URI specification.
     * 
The given parts will automatically get encoded if necessary.
     * @param protocol the URL protocol to use (e.g. "jar" or "file" - without colon);
     * also known as "scheme"
     * @param location the location (e.g. the file path within that protocol);
     * also known as "scheme-specific part"
     * @param fragment the fragment within that location (e.g. anchor on an HTML page,
     * as following after a "#" separator)
     * @throws MalformedURLException if the given URL specification is not valid
     * @see java.net.URI#URI(String, String, String)
     */
    public UrlResource(String protocol, String location, String fragment) throws MalformedURLException  {
        try {
            this.uri = new URI(protocol, location, fragment);
            this.url = this.uri.toURL();
            this.cleanedUrl = getCleanedUrl(this.url, this.uri.toString());
        }
        catch (URISyntaxException ex) {
            MalformedURLException exToThrow = new MalformedURLException(ex.getMessage());
            exToThrow.initCause(ex);
            throw exToThrow;
        }
    }

    /**
     * Determine a cleaned URL for the given original URL.
     * @param originalUrl the original URL
     * @param originalPath the original URL path
     * @return the cleaned URL
     * @see org.springframework.util.StringUtils#cleanPath
     */
    private URL getCleanedUrl(URL originalUrl, String originalPath) {
        try {
            return new URL(StringUtils.cleanPath(originalPath));
        }
        catch (MalformedURLException ex) {
            // Cleaned URL path cannot be converted to URL
            // -> take original URL.
            return originalUrl;
        }
    }


    /**
     * This implementation opens an InputStream for the given URL.
     * It sets the "UseCaches" flag to {@code false},
     * mainly to avoid jar file locking on Windows.
     * @see java.net.URL#openConnection()
     * @see java.net.URLConnection#setUseCaches(boolean)
     * @see java.net.URLConnection#getInputStream()
     */
    public InputStream getInputStream() throws IOException {
        URLConnection con = this.url.openConnection();
        ResourceUtils.useCachesIfNecessary(con);
        try {
            return con.getInputStream();
        }
        catch (IOException ex) {
            // Close the HTTP connection (if applicable).
            if (con instanceof HttpURLConnection) {
                ((HttpURLConnection) con).disconnect();
            }
            throw ex;
        }
    }

    /**
     * This implementation returns the underlying URL reference.
     */
    @Override
    public URL getURL() throws IOException {
        return this.url;
    }

    /**
     * This implementation returns the underlying URI directly,
     * if possible.
     */
    @Override
    public URI getURI() throws IOException {
        if (this.uri != null) {
            return this.uri;
        }
        else {
            return super.getURI();
        }
    }

    /**
     * This implementation returns a File reference for the underlying URL/URI,
     * provided that it refers to a file in the file system.
     * @see org.springframework.util.ResourceUtils#getFile(java.net.URL, String)
     */
    @Override
    public File getFile() throws IOException {
        if (this.uri != null) {
            return super.getFile(this.uri);
        }
        else {
            return super.getFile();
        }
    }

    /**
     * This implementation creates a UrlResource, applying the given path
     * relative to the path of the underlying URL of this resource descriptor.
     * @see java.net.URL#URL(java.net.URL, String)
     */
    @Override
    public Resource createRelative(String relativePath) throws MalformedURLException {
        if (relativePath.startsWith("/")) {
            relativePath = relativePath.substring(1);
        }
        return new UrlResource(new URL(this.url, relativePath));
    }

    /**
     * This implementation returns the name of the file that this URL refers to.
     * @see java.net.URL#getFile()
     * @see java.io.File#getName()
     */
    @Override
    public String getFilename() {
        return new File(this.url.getFile()).getName();
    }

    /**
     * This implementation returns a description that includes the URL.
     */
    public String getDescription() {
        return "URL [" + this.url + "]";
    }


    /**
     * This implementation compares the underlying URL references.
     */
    @Override
    public boolean equals(Object obj) {
        return (obj == this ||
            (obj instanceof UrlResource && this.cleanedUrl.equals(((UrlResource) obj).cleanedUrl)));
    }

    /**
     * This implementation returns the hash code of the underlying URL reference.
     */
    @Override
    public int hashCode() {
        return this.cleanedUrl.hashCode();
    }

}

 

四、 Servlet上下文资源——ServletContextResource

实现基本就是基于 this.servletContext.getResource(this.path) 或 this.servletContext.getResourceAsStream(this.path) 这两个方法。

public class ServletContextResource extends AbstractFileResolvingResource implements ContextResource {

    private final ServletContext servletContext;

    private final String path;


    /**
     * Create a new ServletContextResource.
     * 
The Servlet spec requires that resource paths start with a slash,
     * even if many containers accept paths without leading slash too.
     * Consequently, the given path will be prepended with a slash if it
     * doesn't already start with one.
     * @param servletContext the ServletContext to load from
     * @param path the path of the resource
     */
    public ServletContextResource(ServletContext servletContext, String path) {
        // check ServletContext
        Assert.notNull(servletContext, "Cannot resolve ServletContextResource without ServletContext");
        this.servletContext = servletContext;

        // check path
        Assert.notNull(path, "Path is required");
        String pathToUse = StringUtils.cleanPath(path);
        if (!pathToUse.startsWith("/")) {
            pathToUse = "/" + pathToUse;
        }
        this.path = pathToUse;
    }

    /**
     * Return the ServletContext for this resource.
     */
    public final ServletContext getServletContext() {
        return this.servletContext;
    }

    /**
     * Return the path for this resource.
     */
    public final String getPath() {
        return this.path;
    }


    /**
     * This implementation checks {@code ServletContext.getResource}.
     * @see javax.servlet.ServletContext#getResource(String)
     */
    @Override
    public boolean exists() {
        try {
            URL url = this.servletContext.getResource(this.path);
            return (url != null);
        }
        catch (MalformedURLException ex) {
            return false;
        }
    }

    /**
     * This implementation delegates to {@code ServletContext.getResourceAsStream},
     * which returns {@code null} in case of a non-readable resource (e.g. a directory).
     * @see javax.servlet.ServletContext#getResourceAsStream(String)
     */
    @Override
    public boolean isReadable() {
        InputStream is = this.servletContext.getResourceAsStream(this.path);
        if (is != null) {
            try {
                is.close();
            }
            catch (IOException ex) {
                // ignore
            }
            return true;
        }
        else {
            return false;
        }
    }

    /**
     * This implementation delegates to {@code ServletContext.getResourceAsStream},
     * but throws a FileNotFoundException if no resource found.
     * @see javax.servlet.ServletContext#getResourceAsStream(String)
     */
    public InputStream getInputStream() throws IOException {
        InputStream is = this.servletContext.getResourceAsStream(this.path);
        if (is == null) {
            throw new FileNotFoundException("Could not open " + getDescription());
        }
        return is;
    }

    /**
     * This implementation delegates to {@code ServletContext.getResource},
     * but throws a FileNotFoundException if no resource found.
     * @see javax.servlet.ServletContext#getResource(String)
     */
    @Override
    public URL getURL() throws IOException {
        URL url = this.servletContext.getResource(this.path);
        if (url == null) {
            throw new FileNotFoundException(
                    getDescription() + " cannot be resolved to URL because it does not exist");
        }
        return url;
    }

    /**
     * This implementation resolves "file:" URLs or alternatively delegates to
     * {@code ServletContext.getRealPath}, throwing a FileNotFoundException
     * if not found or not resolvable.
     * @see javax.servlet.ServletContext#getResource(String)
     * @see javax.servlet.ServletContext#getRealPath(String)
     */
    @Override
    public File getFile() throws IOException {
        URL url = this.servletContext.getResource(this.path);
        if (url != null && ResourceUtils.isFileURL(url)) {
            // Proceed with file system resolution...
            return super.getFile();
        }
        else {
            String realPath = WebUtils.getRealPath(this.servletContext, this.path);
            return new File(realPath);
        }
    }

    /**
     * This implementation creates a ServletContextResource, applying the given path
     * relative to the path of the underlying file of this resource descriptor.
     * @see org.springframework.util.StringUtils#applyRelativePath(String, String)
     */
    @Override
    public Resource createRelative(String relativePath) {
        String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
        return new ServletContextResource(this.servletContext, pathToUse);
    }

    /**
     * This implementation returns the name of the file that this ServletContext
     * resource refers to.
     * @see org.springframework.util.StringUtils#getFilename(String)
     */
    @Override
    public String getFilename() {
        return StringUtils.getFilename(this.path);
    }

    /**
     * This implementation returns a description that includes the ServletContext
     * resource location.
     */
    public String getDescription() {
        return "ServletContext resource [" + this.path + "]";
    }

    public String getPathWithinContext() {
        return this.path;
    }


    /**
     * This implementation compares the underlying ServletContext resource locations.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj instanceof ServletContextResource) {
            ServletContextResource otherRes = (ServletContextResource) obj;
            return (this.servletContext.equals(otherRes.servletContext) && this.path.equals(otherRes.path));
        }
        return false;
    }

    /**
     * This implementation returns the hash code of the underlying
     * ServletContext resource location.
     */
    @Override
    public int hashCode() {
        return this.path.hashCode();
    }

}

 

五、其它不常用的实现类

1、字节数组资源——ByteArrayResource

    若需要操作描述一个字节数组，可以用这个资源类。ByteArrayResource可多次读取数组资源。

2、描述性资源——DescriptiveResource

　若一个资源，仅仅有一个描述，非常抽象的这种情况，可以用这个资源类，它并没有指向一个实际的可读的资源。

3、输入流资源——InputStreamResource

　输入流资源InputStreamResource，是一个不可变InputStream的包装和一个不可变的描述字符串。此外还有一个私有成员变量Boolean read用于限制本资源的InputStream不可被重复获取。 这个包装类指向的是一个已经打开的资源，所以它的 isOpen()总是返回true。而且它不能重复获取资源，只能读取一次

4、 VFS资源——VfsResource

     vfs是Virtual File System虚拟文件系统，也称为虚拟文件系统开关（Virtual Filesystem Switch）.是Linux档案系统对外的接口。任何要使用档案系统的程序都必须经由这层接口来使用它。（摘自百度百科...）它能一致的访问物理文件系统、jar资源、zip资源、war资源等，VFS能把这些资源一致的映射到一个目录上，访问它们就像访问物理文件资源一样，而其实这些资源不存在于物理文件系统。

5、 Portlet上下文资源——PortletContextResource

    Portlet是基于java的web组件，由portlet容器管理，并由容器处理请求，生产动态内容。这个资源类封装了一个不可变的javax.portlet.PortletContext对象和一个不可变的String对象代表路径。类中所有操作都基于这两个属性。PortletContextResource对象实现了ContextResource接口，实现了方法String getPathWithinContext()，即返回自身的path属性。

 

http://www.cnblogs.com/zrtqsk/p/4015985.html