1 /*
2 * Copyright 2002-2012 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.io.InputStream;
22 import java.net.URI;
23 import java.net.URL;
24
25 /**
26 * Interface for a resource descriptor that abstracts from the actual
27 * type of underlying resource, such as a file or class path resource.
28 *
29 * <p>An InputStream can be opened for every resource if it exists in
30 * physical form, but a URL or File handle can just be returned for
31 * certain resources. The actual behavior is implementation-specific.
32 *
33 * @author Juergen Hoeller
34 * @since 28.12.2003
35 * @see #getInputStream()
36 * @see #getURL()
37 * @see #getURI()
38 * @see #getFile()
39 * @see WritableResource
40 * @see ContextResource
41 * @see FileSystemResource
42 * @see ClassPathResource
43 * @see UrlResource
44 * @see ByteArrayResource
45 * @see InputStreamResource
46 */
47 public interface Resource extends InputStreamSource {
48
49 /**
50 * Return whether this resource actually exists in physical form.
51 * <p>This method performs a definitive existence check, whereas the
52 * existence of a <code>Resource</code> handle only guarantees a
53 * valid descriptor handle.
54 */
55 boolean exists();
56
57 /**
58 * Return whether the contents of this resource can be read,
59 * e.g. via {@link #getInputStream()} or {@link #getFile()}.
60 * <p>Will be <code>true</code> for typical resource descriptors;
61 * note that actual content reading may still fail when attempted.
62 * However, a value of <code>false</code> is a definitive indication
63 * that the resource content cannot be read.
64 * @see #getInputStream()
65 */
66 boolean isReadable();
67
68 /**
69 * Return whether this resource represents a handle with an open
70 * stream. If true, the InputStream cannot be read multiple times,
71 * and must be read and closed to avoid resource leaks.
72 * <p>Will be <code>false</code> for typical resource descriptors.
73 */
74 boolean isOpen();
75
76 /**
77 * Return a URL handle for this resource.
78 * @throws IOException if the resource cannot be resolved as URL,
79 * i.e. if the resource is not available as descriptor
80 */
81 URL getURL() throws IOException;
82
83 /**
84 * Return a URI handle for this resource.
85 * @throws IOException if the resource cannot be resolved as URI,
86 * i.e. if the resource is not available as descriptor
87 */
88 URI getURI() throws IOException;
89
90 /**
91 * Return a File handle for this resource.
92 * @throws IOException if the resource cannot be resolved as absolute
93 * file path, i.e. if the resource is not available in a file system
94 */
95 File getFile() throws IOException;
96
97 /**
98 * Determine the content length for this resource.
99 * @throws IOException if the resource cannot be resolved
100 * (in the file system or as some other known physical resource type)
101 */
102 long contentLength() throws IOException;
103
104 /**
105 * Determine the last-modified timestamp for this resource.
106 * @throws IOException if the resource cannot be resolved
107 * (in the file system or as some other known physical resource type)
108 */
109 long lastModified() throws IOException;
110
111 /**
112 * Create a resource relative to this resource.
113 * @param relativePath the relative path (relative to this resource)
114 * @return the resource handle for the relative resource
115 * @throws IOException if the relative resource cannot be determined
116 */
117 Resource createRelative(String relativePath) throws IOException;
118
119 /**
120 * Determine a filename for this resource, i.e. typically the last
121 * part of the path: for example, "myfile.txt".
122 * <p>Returns <code>null</code> if this type of resource does not
123 * have a filename.
124 */
125 String getFilename();
126
127 /**
128 * Return a description for this resource,
129 * to be used for error output when working with the resource.
130 * <p>Implementations are also encouraged to return this value
131 * from their <code>toString</code> method.
132 * @see java.lang.Object#toString()
133 */
134 String getDescription();
135
136 }