Resource


1   /*
2    * Copyright 2002-2005 the original author or authors.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.core.io;
18  
19  import java.io.File  ;
20  import java.io.IOException  ;
21  import java.net.URL  ;
22  
23  /**
24   * Interface for a resource descriptor that abstracts from the actual
25   * type of underlying resource, such as a file or class path resource.
26   *
27   * <p>An InputStream can be opened for every resource if it exists in
28   * physical form, but a URL or File handle can just be returned for
29   * certain resources. The actual behavior is implementation-specific.
30   *
31   * @author Juergen Hoeller
32   * @since 28.12.2003
33   * @see #getInputStream()
34   * @see #getURL()
35   * @see #getFile()
36   * @see FileSystemResource
37   * @see ClassPathResource
38   * @see UrlResource
39   * @see ByteArrayResource
40   * @see InputStreamResource
41   * @see org.springframework.web.context.support.ServletContextResource
42   */
43  public interface Resource extends InputStreamSource {
44  
45      /**
46       * Return whether this resource actually exists in physical form.
47       */
48      boolean exists();
49  
50      /**
51       * Return whether this resource represents a handle with an open
52       * stream. If true, the InputStream cannot be read multiple times,
53       * and must be read and closed to avoid resource leaks.
54       * <p>Will be false for all usual resource descriptors.
55       */
56      boolean isOpen();
57  
58      /**
59       * Return a URL handle for this resource.
60       * @throws IOException if the resource cannot be resolved as URL,
61       * i.e. if the resource is not available as descriptor
62       */
63      URL   getURL() throws IOException  ;
64  
65      /**
66       * Return a File handle for this resource.
67       * @throws IOException if the resource cannot be resolved as absolute
68       * file path, i.e. if the resource is not available in a file system
69       */
70      File   getFile() throws IOException  ;
71  
72      /**
73       * Create a resource relative to this resource.
74       * @param relativePath the relative path (relative to this resource)
75       * @return the resource handle for the relative resource
76       * @throws IOException if the relative resource cannot be determined
77       */
78      Resource createRelative(String   relativePath) throws IOException  ;
79  
80      /**
81       * Return a filename for this resource, i.e. typically the last
82       * part of the path: for example, "myfile.txt".
83       */
84      String   getFilename();
85  
86      /**
87       * Return a description for this resource,
88       * to be used for error output when working with the resource.
89       * <p>Implementations are also encouraged to return this value
90       * from their <code>toString</code> method.
91       * @see java.lang.Object#toString
92       */
93      String   getDescription();
94  
95  }
96
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