content: /*
   * Copyright 2002-2018 the original author or authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.alibaba.nacos.common.packagescan.resource;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URI;
  import java.net.URL;
  import java.nio.channels.Channels;
  import java.nio.channels.ReadableByteChannel;
  
  /**
   * Copy from https://github.com/spring-projects/spring-framework.git, with less modifications
   * 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
   * @see #getInputStream()
   * @see #getUrl()
   * @see #getUri()
   * @see #getFile()
   * @see WritableResource
   * @see ContextResource
   * @see UrlResource
   * @see FileUrlResource
   * @see FileSystemResource
   * @see ClassPathResource
   * @see ByteArrayResource
   * @see InputStreamResource
   * @since 28.12.2003
   */
  public interface Resource extends InputStreamSource {
  
      /**
       * Determine 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();
  
      /**
       * Indicate whether non-empty contents of this resource can be read via
       * {@link #getInputStream()}.
       *
       * <p>Will be {@code true} for typical resource descriptors that exist
       * since it strictly implies {@link #exists()} semantics as of 5.1.
       * 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()
       * @see #exists()
       */
      default boolean isReadable() {
          return exists();
      }
  
      /**
       * Indicate whether this resource represents a handle with an open stream.
       * If {@code 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.
       */
      default boolean isOpen() {
          return false;
      }
  
      /**
       * Determine whether this resource represents a file in a file system.
       * A value of {@code true} strongly suggests (but does not guarantee)
       * that a {@link #getFile()} call will succeed.
       *
       * <p>This is conservatively {@code false} by default.
       *
       * @see #getFile()
       * @since 5.0
       */
      default boolean isFile() {
          return false;
      }
  
      /**
       * 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
       * @since 2.5
       */
      URI getUri() throws IOException;
  
      /**
       * Return a File handle for this resource.
       *
       * @throws java.io.FileNotFoundException if the resource cannot be resolved as
       *                                       absolute file path, i.e. if the resource is not available in a file system
       * @throws IOException                   in case of general resolution/reading failures
       * @see #getInputStream()
       */
      File getFile() throws IOException;
  
      /**
       * Return a {@link ReadableByteChannel}.
       *
       * <p>It is expected that each call creates a <i>fresh</i> channel.
       *
       * <p>The default implementation returns {@link Channels#newChannel(InputStream)}
       * with the result of {@link #getInputStream()}.
       *
       * @return the byte channel for the underlying resource (must not be {@code null})
       * @throws java.io.FileNotFoundException if the underlying resource doesn't exist
       * @throws IOException                   if the content channel could not be opened
       * @see #getInputStream()
       * @since 5.0
       */
      default ReadableByteChannel readableChannel() throws IOException {
          return Channels.newChannel(getInputStream());
      }
  
      /**
       * 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();
  
  }
  