本文共 4795 字，大约阅读时间需要 15 分钟。
/** * Interface for a resource descriptor that abstracts from the actual * type of underlying resource, such as a file or class path resource. * *An InputStream can be opened for every resource if it exists in * physical form, but a URL or File handle can just be returned for * certain resources. The actual behavior is implementation-specific. * * @author Juergen Hoeller * @since 28.12.2003 * @see #getInputStream() * @see #getURL() * @see #getURI() * @see #getFile() * @see WritableResource * @see ContextResource * @see FileSystemResource * @see ClassPathResource * @see UrlResource * @see ByteArrayResource * @see InputStreamResource * @see PathResource */public interface Resource extends InputStreamSource { /** * Return whether this resource actually exists in physical form. *
This method performs a definitive existence check, whereas the * existence of a {@code Resource} handle only guarantees a * valid descriptor handle. */ boolean exists(); /** * Return whether the contents of this resource can be read, * e.g. via {@link #getInputStream()} or {@link #getFile()}. *
Will be {@code true} for typical resource descriptors; * note that actual content reading may still fail when attempted. * However, a value of {@code false} is a definitive indication * that the resource content cannot be read. * @see #getInputStream() */ boolean isReadable(); /** * Return whether this resource represents a handle with an open * stream. If true, the InputStream cannot be read multiple times, * and must be read and closed to avoid resource leaks. *
Will be {@code false} for typical resource descriptors. */ boolean isOpen(); /** * Return a URL handle for this resource. * @throws IOException if the resource cannot be resolved as URL, * i.e. if the resource is not available as descriptor */ URL getURL() throws IOException; /** * Return a URI handle for this resource. * @throws IOException if the resource cannot be resolved as URI, * i.e. if the resource is not available as descriptor */ URI getURI() throws IOException; /** * Return a File handle for this resource. * @throws IOException if the resource cannot be resolved as absolute * file path, i.e. if the resource is not available in a file system */ File getFile() throws IOException; /** * Determine the content length for this resource. * @throws IOException if the resource cannot be resolved * (in the file system or as some other known physical resource type) */ long contentLength() throws IOException; /** * Determine the last-modified timestamp for this resource. * @throws IOException if the resource cannot be resolved * (in the file system or as some other known physical resource type) */ long lastModified() throws IOException; /** * Create a resource relative to this resource. * @param relativePath the relative path (relative to this resource) * @return the resource handle for the relative resource * @throws IOException if the relative resource cannot be determined */ Resource createRelative(String relativePath) throws IOException; /** * Determine a filename for this resource, i.e. typically the last * part of the path: for example, "myfile.txt". *
Returns {@code null} if this type of resource does not * have a filename. */ String getFilename(); /** * Return a description for this resource, * to be used for error output when working with the resource. *
Implementations are also encouraged to return this value * from their {@code toString} method. * @see Object#toString() */ String getDescription();}
对于不同来源的资源文件都有相应的Resource实现：
1. 文件（FileSystemResource）
2. Classpath资源（ClassPathResource）
3. URL资源（UrlResource）
4. InputStream资源（InputStreamResource）
5. Byte数组资源（ByteArrayResource）等。
ClassPathResource实现：
this.class.getResourceAsStream(this.path);
FileSystemResource实现：
new FileInputStream(this.file);
发表评论
最新留言
关于作者
