1 /*
2 * Copyright 2007 Joachim Grueneis
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14 package org.exolab.castor.xml.util.resolvers;
15
16 import org.apache.commons.logging.Log;
17 import org.apache.commons.logging.LogFactory;
18
19
20 /**
21 * Some helpers used by the resolver commands. This is a utility class which is NOT meant to be
22 * instantiated.
23 *
24 * @author <a href="mailto:jgrueneis AT gmail DOT com">Joachim Grueneis</a>
25 * @version $Revision$ $Date$
26 * @since 1.2
27 */
28 public final class ResolveHelpers {
29 private static final Log LOG = LogFactory.getLog(ResolveHelpers.class);
30
31 /**
32 * A private constructor as this is a utility class without an own state.
33 */
34 private ResolveHelpers() {}
35
36 /**
37 * Qualifies the given <code>fileName</code> with the given <code>packageName</code> and returns
38 * the resulting file path.<br>
39 * If <code>packageName</code> is <code>null</code> or a zero-length String, this method will
40 * return <code>fileName</code>.<br>
41 *
42 * @param fileName The file name to be qualified.
43 * @param packageName The package name to be used for qualifying.
44 * @return The qualified file path.
45 */
46 public static String getQualifiedFileName(String fileName, String packageName) {
47 if (packageName == null || packageName.isEmpty()) {
48 return fileName;
49 }
50
51 return packageName.replace('.', '/') + '/' + fileName;
52 } // -- getQualifiedFileName
53
54 /**
55 * Gets the package name of the given class name.
56 *
57 * @param className The class name to retrieve the package name from.
58 * @return The package name or the empty String if <code>className</code> is <code>null</code> or
59 * does not contain a package.
60 */
61 public static String getPackageName(String className) {
62 if (className == null) {
63 return "";
64 }
65
66 int idx = className.lastIndexOf('.');
67 if (idx >= 0) {
68 return className.substring(0, idx);
69 }
70 return "";
71 } // -- getPackageName
72
73 /**
74 * Compares the two strings for equality. A Null and empty strings are considered equal.
75 *
76 * @return true if the two strings are considered equal.
77 */
78 public static boolean namespaceEquals(String ns1, String ns2) {
79 if (ns1 == null) {
80 return ns2 == null || ns2.length() == 0;
81 }
82
83 if (ns2 == null) {
84 return ns1.length() == 0;
85 }
86
87 return ns1.equals(ns2);
88 } // -- namespaceEquals
89
90 /**
91 * Gets the <code>ClassLoader</code> that's actually to be used (e.g. for loading resources).<br>
92 * The actual <code>ClassLoader</code> is determined in the following way: <lu>
93 * <li>If the passed in "preferred" loader is not <code>null</code>, it is used.
94 * <li>If the loader of this XMLClassDescriptor is not <code>null</code>, it is used.
95 * <li>The context class loader of the current thread is used. </lu>
96 *
97 * @param loader The "preferred" <code>ClassLoader</code>.
98 * @return The loader to be used.
99 */
100 public static ClassLoader getClassLoader(ClassLoader loader) {
101 if (loader != null) {
102 return loader;
103 }
104
105 return Thread.currentThread().getContextClassLoader();
106 } // -- getClassLoader
107
108 /**
109 * Capsulates the ClassLoader.loadClass method to throw no exceptions but return null instead. Any
110 * exception caught are logged with info severity.
111 *
112 * @param classLoader the class loader to use
113 * @param className the class to load
114 * @return the loaded Class or null
115 */
116 public static Class loadClass(ClassLoader classLoader, String className) {
117 if (classLoader == null) {
118 String message = "Argument class loader must not be null";
119 LOG.warn(message);
120 throw new IllegalArgumentException(message);
121 }
122
123 if ((className == null) || (className.length() == 0)) {
124 LOG.debug("Name of class to load is null or empty -> ignored!");
125 return null;
126 }
127
128 try {
129 return classLoader.loadClass(className);
130 } catch (ClassNotFoundException e) {
131 if (LOG.isDebugEnabled()) {
132 LOG.debug("Ignored problem at loading class: " + className + " through class loader: "
133 + classLoader + ", exception: " + e);
134 }
135 return null;
136 }
137 } // -- loadClass
138 }