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linux编程_Spring 设置资源Resource

云返利网 未命名 2020-05-26 09:07:01 20 0

Java中,差别泉源的资源抽象成URL,通过注册差别的handler(URLStreamHandler)来处置差别泉源的资源的读取逻辑。一样平常handler的类型使用差别的前缀(协议,protocal)来识别,如:“file:”、“http:“、”jar:”等。

对于Spring,URL没有界说响应的,如“classpath:“的handler,界说也相对贫苦,Spring对设置文件的读取做了响应的封装,通过Resource接口来抽象底层资源。如下:

/**
 * Interface for a resource descriptor that abstracts from the actual
 * type of underlying resource, such as a file or class path resource.
 *
 * <p>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.
    * <p>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()}.
    * <p>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.
    * <p>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".
    * <p>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.
    * <p>Implementations are also encouraged to return this value
    * from their {@code toString} method.
    * @see Object#toString()
    */
    String getDescription();

}

对于差别泉源的资源文件都有响应的Resource实现,文件(FileSystemResource)、Classpath资源(ClassPathResource)、URL资源(UrlResource)、InputStream资源(InputStreamResource)、Byte数组资源(ByteArrayResource)等。

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