01: /*
02: * Copyright 2002-2005 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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: }
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