1 /*
2 * Copyright 2012 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.ci.config.load;
17
18 import java.io.File;
19 import java.io.FileNotFoundException;
20 import java.io.InputStream;
21 import java.net.URL;
22 import java.net.URLClassLoader;
23
24 import org.xml.sax.InputSource;
25
26 /**
27 * Manages locations to look for configuration files to load.
28 */
29 public final class LocationManager
30 {
31 // ********************************* Fields *********************************
32
33 // --- constants ------------------------------------------------------------
34
35 // --- members --------------------------------------------------------------
36
37 /**
38 * The locations to search for configuration files.
39 */
40 private DynamicUrlClassLoader locations;
41
42 // ****************************** Initializer *******************************
43
44 // ****************************** Constructors ******************************
45
46 /**
47 * Convenience constructor if no class loader should be used as a parent.
48 */
49 public LocationManager()
50 {
51 this(null);
52 }
53
54 /**
55 * Default constructor.
56 *
57 * @param parentClassLoader the parent class loader to delegate requests to.
58 * May be <code>null</code>.
59 */
60 public LocationManager(final ClassLoader parentClassLoader)
61 {
62 locations = new DynamicUrlClassLoader(new URL[0], parentClassLoader);
63 }
64
65 // ****************************** Inner Classes *****************************
66
67 /**
68 * Implementation allows to add new locations dynamically.
69 */
70 private static final class DynamicUrlClassLoader extends URLClassLoader
71 {
72 private DynamicUrlClassLoader(final URL[] urls,
73 final ClassLoader parentClassLoader)
74 {
75 super(urls, parentClassLoader);
76 }
77
78 private void addUrl(final URL url)
79 {
80 super.addURL(url);
81 }
82 }
83
84 // ********************************* Methods ********************************
85
86 // --- init -----------------------------------------------------------------
87
88 // --- get&set --------------------------------------------------------------
89
90 // --- business -------------------------------------------------------------
91
92 /**
93 * Adds a file location to the manager to search for configuration files.
94 *
95 * @param file the file location to be added. May reference a folder or a JAR
96 * file.
97 * @throws NullPointerException if {@link file} is <code>null</code>.
98 * @throws IllegalArgumentException if {@code file} does not provide a valid
99 * URL.
100 */
101 public void addLocation(final File file) throws NullPointerException,
102 IllegalArgumentException
103 {
104 try
105 {
106 final URL url = file.toURI().toURL();
107 addLocation(url);
108 }
109 catch (final Exception e)
110 {
111 throw new IllegalArgumentException(
112 file.getAbsolutePath()
113 + " is not a valid file. Cannot create a URL location.", e);
114 }
115 }
116
117 /**
118 * Adds an URL location to the manager to search for configuration files.
119 *
120 * @param url the URL location to be added. May reference a folder or a JAR
121 * file.
122 */
123 public void addLocation(final URL url)
124 {
125 locations.addUrl(url);
126 }
127
128 /**
129 * Opens a stream to the given resource, if the resource can be found at any
130 * location managed by this instance.
131 * <p>
132 * The client is responsible to close the resource.
133 * </p>
134 *
135 * @param resource the resource to open.
136 * @return the stream to the resource as an input source.
137 * @throws FileNotFoundException if the resource cannot be opened.
138 */
139 public InputSource open(final String resource) throws FileNotFoundException
140 {
141 final URL url = locations.getResource(resource);
142 if (url != null)
143 {
144 final InputStream in = locations.getResourceAsStream(resource);
145 final InputSource source = new InputSource(in);
146 source.setSystemId(url.toExternalForm());
147 return source;
148 }
149
150 throw new FileNotFoundException("Cannot find resource '" + resource + "'.");
151 }
152
153 // --- object basics --------------------------------------------------------
154
155 }