ClassResourceLoader.java revision 05c4888988880a2dd74efc90ea72d9a6b2501455 
1/*
2 * Copyright (C) 2010 Google Inc.
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
17package com.google.clearsilver.jsilver.resourceloader;
18
19import com.google.clearsilver.jsilver.exceptions.JSilverTemplateNotFoundException;
20
21import java.io.IOException;
22import java.io.InputStream;
23import java.io.InputStreamReader;
24import java.io.Reader;
25
26/**
27 * Loads resources from classpath, alongside a given class.
28 *
29 * <p>For example, suppose the classpath contains:
30 * <pre>
31 * com/foo/SomeThing.class
32 * com/foo/my-template.cs
33 * com/foo/subdir/another-template.cs
34 * </pre>
35 *
36 * <p>You can access the resources in the class's package like this:
37 * <pre>
38 * ResourceLoader loader = new ClassResourceLoader(SomeThing.class);
39 * loader.open("my-template.cs");
40 * loader.open("subdir/my-template.cs");
41 * </pre>
42 * Or by using a relative path:
43 * <pre>
44 * ResourceLoader loader = new ClassResourceLoader(Something.class, "subdir");
45 * loader.open("my-template.cs");
46 * </pre>
47 *
48 * @see ResourceLoader
49 * @see ClassLoaderResourceLoader
50 */
51public class ClassResourceLoader extends BufferedResourceLoader {
52
53  private final Class<?> cls;
54  private final String basePath;
55
56  public ClassResourceLoader(Class<?> cls) {
57    this.cls = cls;
58    this.basePath = "/" + cls.getPackage().getName().replace('.', '/');
59  }
60
61  /**
62   * Load resources from the given subdirectory {@code basePath},
63   * relative to the .class file of {@code cls}.
64   */
65  public ClassResourceLoader(Class<?> cls, String basePath) {
66    this.cls = cls;
67    this.basePath = basePath;
68  }
69
70  @Override
71  public Reader open(String name) throws IOException {
72    InputStream stream = cls.getResourceAsStream(basePath + '/' + name);
73    return stream == null ? null : buffer(new InputStreamReader(stream, getCharacterSet()));
74  }
75
76  @Override
77  public Reader openOrFail(String name) throws JSilverTemplateNotFoundException, IOException {
78    Reader reader = open(name);
79    if (reader == null) {
80      throw new JSilverTemplateNotFoundException("No '" + name + "' as class resource of "
81          + cls.getName());
82    } else {
83      return reader;
84    }
85  }
86
87}
88