1 /*
2 * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
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 package de.smartics.properties.spi.core.util;
17
18 import java.net.URL;
19
20 import de.smartics.util.lang.classpath.ClassPathContext;
21
22 /**
23 * Utilities dealing with class loaders.
24 */
25 public final class ClassLoaderUtils
26 {
27 // ********************************* Fields *********************************
28
29 // --- constants ------------------------------------------------------------
30
31 // --- members --------------------------------------------------------------
32
33 // ****************************** Initializer *******************************
34
35 // ****************************** Constructors ******************************
36
37 private ClassLoaderUtils()
38 {
39 }
40
41 // ****************************** Inner Classes *****************************
42
43 // ********************************* Methods ********************************
44
45 // --- init -----------------------------------------------------------------
46
47 // --- get&set --------------------------------------------------------------
48
49 // --- business -------------------------------------------------------------
50
51 /**
52 * Determines the path to the class loader root that contains the given
53 * {@code type}.
54 *
55 * @param type the type whose class loader root is requested.
56 * @return the class loader root.
57 * @throws NullPointerException if {@code type} is <code>null</code>.
58 */
59 public static String calcArchivePath(final Class<?> type)
60 throws NullPointerException
61 {
62 final ClassLoader loader = type.getClassLoader();
63 final String resource = type.getName().replace('.', '/') + ".class";
64 final String path = calcFirstArchivePath(loader, resource);
65 return path;
66 }
67
68 /**
69 * Determines the path to the class loader root that contains the given
70 * {@code resource}. The first matching path is returned. This call does not
71 * check if there is more than one path that serves the given {@code resource}
72 * .
73 *
74 * @param loader the loader to load the resource.
75 * @param resource the resource whose class loader root is requested.
76 * @return the class loader root for the given {@code resource}.
77 * @throws NullPointerException if {@code loader} or {@code resource} is
78 * <code>null</code>.
79 * @throws IllegalArgumentException if the resource cannot be found by the
80 * given class loader.
81 */
82 public static String calcFirstArchivePath(final ClassLoader loader,
83 final String resource) throws NullPointerException,
84 IllegalArgumentException
85 {
86 final URL url = loader.getResource(resource);
87 if (url == null)
88 {
89 throw new IllegalArgumentException(
90 "The resource '" + resource
91 + "' cannot be found by the given class loader.");
92 }
93 final String urlString = url.toExternalForm();
94 final int endIndex = urlString.length() - resource.length();
95 final String path = urlString.substring(0, endIndex);
96 return path;
97 }
98
99 /**
100 * Creates the class path context for the given class loader and its derived
101 * context root. The first matching path is used to calculate the class path
102 * root. This call does not check if there is more than one path that serves
103 * the given {@code resource}.
104 *
105 * @param classLoader the class loader to access resources.
106 * @param resource the resource whose class loader root is requested.
107 * @return the class path context.
108 */
109 public static ClassPathContext createClassPathContext(
110 final ClassLoader classLoader, final String resource)
111 {
112 final String root = calcFirstArchivePath(classLoader, resource);
113 return new ClassPathContext(classLoader, root);
114 }
115
116 // --- object basics --------------------------------------------------------
117
118 }