Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
ResolverUtil |
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| 0.0;0 |
1 | /** |
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2 | * |
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3 | * Licensed to the Apache Software Foundation (ASF) under one or more |
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4 | * contributor license agreements. See the NOTICE file distributed with |
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5 | * this work for additional information regarding copyright ownership. |
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6 | * The ASF licenses this file to You under the Apache License, Version 2.0 |
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7 | * (the "License"); you may not use this file except in compliance with |
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8 | * the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | package org.apache.camel.util; |
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19 | ||
20 | import org.apache.commons.logging.Log; |
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21 | import org.apache.commons.logging.LogFactory; |
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22 | ||
23 | import java.lang.annotation.Annotation; |
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24 | import java.util.Set; |
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25 | import java.util.HashSet; |
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26 | import java.util.Enumeration; |
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27 | import java.util.jar.JarEntry; |
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28 | import java.util.jar.JarInputStream; |
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29 | import java.net.URL; |
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30 | import java.net.URLDecoder; |
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31 | import java.io.IOException; |
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32 | import java.io.File; |
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33 | import java.io.FileInputStream; |
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34 | ||
35 | /** |
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36 | * <p>ResolverUtil is used to locate classes that are available in the/a class path and meet |
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37 | * arbitrary conditions. The two most common conditions are that a class implements/extends |
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38 | * another class, or that is it annotated with a specific annotation. However, through the use |
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39 | * of the {@link Test} class it is possible to search using arbitrary conditions.</p> |
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40 | * |
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41 | * <p>A ClassLoader is used to locate all locations (directories and jar files) in the class |
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42 | * path that contain classes within certain packages, and then to load those classes and |
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43 | * check them. By default the ClassLoader returned by |
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44 | * {@code Thread.currentThread().getContextClassLoader()} is used, but this can be overridden |
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45 | * by calling {@link #setClassLoader(ClassLoader)} prior to invoking any of the {@code find()} |
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46 | * methods.</p> |
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47 | * |
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48 | * <p>General searches are initiated by calling the |
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49 | * {@link #find(ResolverUtil.Test, String)} ()} method and supplying |
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50 | * a package name and a Test instance. This will cause the named package <b>and all sub-packages</b> |
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51 | * to be scanned for classes that meet the test. There are also utility methods for the common |
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52 | * use cases of scanning multiple packages for extensions of particular classes, or classes |
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53 | * annotated with a specific annotation.</p> |
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54 | * |
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55 | * <p>The standard usage pattern for the ResolverUtil class is as follows:</p> |
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56 | * |
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57 | *<pre> |
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58 | *ResolverUtil<ActionBean> resolver = new ResolverUtil<ActionBean>(); |
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59 | *resolver.findImplementation(ActionBean.class, pkg1, pkg2); |
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60 | *resolver.find(new CustomTest(), pkg1); |
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61 | *resolver.find(new CustomTest(), pkg2); |
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62 | *Collection<ActionBean> beans = resolver.getClasses(); |
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63 | *</pre> |
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64 | * |
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65 | * @author Tim Fennell |
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66 | */ |
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67 | 58 | public class ResolverUtil<T> { |
68 | 1 | private static final transient Log log = LogFactory.getLog(ResolverUtil.class); |
69 | ||
70 | /** |
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71 | * A simple interface that specifies how to test classes to determine if they |
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72 | * are to be included in the results produced by the ResolverUtil. |
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73 | */ |
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74 | public static interface Test { |
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75 | /** |
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76 | * Will be called repeatedly with candidate classes. Must return True if a class |
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77 | * is to be included in the results, false otherwise. |
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78 | */ |
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79 | boolean matches(Class type); |
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80 | } |
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81 | ||
82 | /** |
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83 | * A Test that checks to see if each class is assignable to the provided class. Note |
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84 | * that this test will match the parent type itself if it is presented for matching. |
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85 | */ |
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86 | public static class IsA implements Test { |
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87 | private Class parent; |
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88 | ||
89 | /** Constructs an IsA test using the supplied Class as the parent class/interface. */ |
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90 | 0 | public IsA(Class parentType) { this.parent = parentType; } |
91 | ||
92 | /** Returns true if type is assignable to the parent type supplied in the constructor. */ |
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93 | public boolean matches(Class type) { |
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94 | 0 | return type != null && parent.isAssignableFrom(type); |
95 | } |
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96 | ||
97 | @Override public String toString() { |
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98 | 0 | return "is assignable to " + parent.getSimpleName(); |
99 | } |
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100 | } |
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101 | ||
102 | /** |
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103 | * A Test that checks to see if each class is annotated with a specific annotation. If it |
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104 | * is, then the test returns true, otherwise false. |
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105 | */ |
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106 | public static class AnnotatedWith implements Test { |
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107 | private Class<? extends Annotation> annotation; |
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108 | ||
109 | /** Construts an AnnotatedWith test for the specified annotation type. */ |
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110 | 34 | public AnnotatedWith(Class<? extends Annotation> annotation) { this.annotation = annotation; } |
111 | ||
112 | /** Returns true if the type is annotated with the class provided to the constructor. */ |
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113 | public boolean matches(Class type) { |
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114 | 374 | return type != null && type.isAnnotationPresent(annotation); |
115 | } |
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116 | ||
117 | @Override public String toString() { |
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118 | 442 | return "annotated with @" + annotation.getSimpleName(); |
119 | } |
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120 | } |
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121 | ||
122 | /** The set of matches being accumulated. */ |
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123 | 58 | private Set<Class<? extends T>> matches = new HashSet<Class<?extends T>>(); |
124 | ||
125 | /** |
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126 | * The ClassLoader to use when looking for classes. If null then the ClassLoader returned |
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127 | * by Thread.currentThread().getContextClassLoader() will be used. |
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128 | */ |
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129 | private ClassLoader classloader; |
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130 | ||
131 | /** |
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132 | * Provides access to the classes discovered so far. If no calls have been made to |
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133 | * any of the {@code find()} methods, this set will be empty. |
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134 | * |
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135 | * @return the set of classes that have been discovered. |
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136 | */ |
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137 | public Set<Class<? extends T>> getClasses() { |
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138 | 34 | return matches; |
139 | } |
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140 | ||
141 | /** |
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142 | * Returns the classloader that will be used for scanning for classes. If no explicit |
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143 | * ClassLoader has been set by the calling, the context class loader will be used. |
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144 | * |
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145 | * @return the ClassLoader that will be used to scan for classes |
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146 | */ |
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147 | public ClassLoader getClassLoader() { |
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148 | 408 | return classloader == null ? Thread.currentThread().getContextClassLoader() : classloader; |
149 | } |
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150 | ||
151 | /** |
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152 | * Sets an explicit ClassLoader that should be used when scanning for classes. If none |
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153 | * is set then the context classloader will be used. |
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154 | * |
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155 | * @param classloader a ClassLoader to use when scanning for classes |
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156 | */ |
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157 | 0 | public void setClassLoader(ClassLoader classloader) { this.classloader = classloader; } |
158 | ||
159 | /** |
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160 | * Attempts to discover classes that are assignable to the type provided. In the case |
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161 | * that an interface is provided this method will collect implementations. In the case |
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162 | * of a non-interface class, subclasses will be collected. Accumulated classes can be |
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163 | * accessed by calling {@link #getClasses()}. |
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164 | * |
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165 | * @param parent the class of interface to find subclasses or implementations of |
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166 | * @param packageNames one or more package names to scan (including subpackages) for classes |
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167 | */ |
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168 | public void findImplementations(Class parent, String... packageNames) { |
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169 | 0 | if (packageNames == null) return; |
170 | ||
171 | 0 | Test test = new IsA(parent); |
172 | 0 | for (String pkg : packageNames) { |
173 | 0 | find(test, pkg); |
174 | } |
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175 | 0 | } |
176 | ||
177 | /** |
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178 | * Attempts to discover classes that are annotated with to the annotation. Accumulated |
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179 | * classes can be accessed by calling {@link #getClasses()}. |
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180 | * |
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181 | * @param annotation the annotation that should be present on matching classes |
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182 | * @param packageNames one or more package names to scan (including subpackages) for classes |
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183 | */ |
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184 | public void findAnnotated(Class<? extends Annotation> annotation, String... packageNames) { |
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185 | 34 | if (packageNames == null) return; |
186 | ||
187 | 34 | Test test = new AnnotatedWith(annotation); |
188 | 68 | for (String pkg : packageNames) { |
189 | 34 | find(test, pkg); |
190 | } |
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191 | 34 | } |
192 | ||
193 | /** |
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194 | * Scans for classes starting at the package provided and descending into subpackages. |
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195 | * Each class is offered up to the Test as it is discovered, and if the Test returns |
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196 | * true the class is retained. Accumulated classes can be fetched by calling |
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197 | * {@link #getClasses()}. |
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198 | * |
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199 | * @param test an instance of {@link Test} that will be used to filter classes |
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200 | * @param packageName the name of the package from which to start scanning for |
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201 | * classes, e.g. {@code net.sourceforge.stripes} |
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202 | */ |
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203 | public void find(Test test, String packageName) { |
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204 | 34 | packageName = packageName.replace('.', '/'); |
205 | 34 | ClassLoader loader = getClassLoader(); |
206 | Enumeration<URL> urls; |
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207 | ||
208 | try { |
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209 | 34 | urls = loader.getResources(packageName); |
210 | } |
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211 | 0 | catch (IOException ioe) { |
212 | 0 | log.warn("Could not read package: " + packageName, ioe); |
213 | 0 | return; |
214 | 34 | } |
215 | ||
216 | 102 | while (urls.hasMoreElements()) { |
217 | try { |
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218 | 68 | String urlPath = urls.nextElement().getFile(); |
219 | 68 | urlPath = URLDecoder.decode(urlPath, "UTF-8"); |
220 | ||
221 | // If it's a file in a directory, trim the stupid file: spec |
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222 | 68 | if ( urlPath.startsWith("file:") ) { |
223 | 0 | urlPath = urlPath.substring(5); |
224 | } |
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225 | ||
226 | // Else it's in a JAR, grab the path to the jar |
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227 | 68 | if (urlPath.indexOf('!') > 0) { |
228 | 0 | urlPath = urlPath.substring(0, urlPath.indexOf('!')); |
229 | } |
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230 | ||
231 | 68 | log.debug("Scanning for classes in [" + urlPath + "] matching criteria: " + test); |
232 | 68 | File file = new File(urlPath); |
233 | 68 | if ( file.isDirectory() ) { |
234 | 68 | loadImplementationsInDirectory(test, packageName, file); |
235 | 68 | } |
236 | else { |
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237 | 0 | loadImplementationsInJar(test, packageName, file); |
238 | } |
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239 | } |
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240 | 0 | catch (IOException ioe) { |
241 | 0 | log.warn("could not read entries", ioe); |
242 | 68 | } |
243 | 0 | } |
244 | 34 | } |
245 | ||
246 | ||
247 | /** |
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248 | * Finds matches in a physical directory on a filesystem. Examines all |
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249 | * files within a directory - if the File object is not a directory, and ends with <i>.class</i> |
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250 | * the file is loaded and tested to see if it is acceptable according to the Test. Operates |
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251 | * recursively to find classes within a folder structure matching the package structure. |
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252 | * |
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253 | * @param test a Test used to filter the classes that are discovered |
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254 | * @param parent the package name up to this directory in the package hierarchy. E.g. if |
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255 | * /classes is in the classpath and we wish to examine files in /classes/org/apache then |
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256 | * the values of <i>parent</i> would be <i>org/apache</i> |
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257 | * @param location a File object representing a directory |
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258 | */ |
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259 | private void loadImplementationsInDirectory(Test test, String parent, File location) { |
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260 | 102 | File[] files = location.listFiles(); |
261 | 102 | StringBuilder builder = null; |
262 | ||
263 | 510 | for (File file : files) { |
264 | 408 | builder = new StringBuilder(100); |
265 | 408 | builder.append(parent).append("/").append(file.getName()); |
266 | 408 | String packageOrClass = ( parent == null ? file.getName() : builder.toString() ); |
267 | ||
268 | 408 | if (file.isDirectory()) { |
269 | 34 | loadImplementationsInDirectory(test, packageOrClass, file); |
270 | 34 | } |
271 | 374 | else if (file.getName().endsWith(".class")) { |
272 | 374 | addIfMatching(test, packageOrClass); |
273 | } |
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274 | } |
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275 | 102 | } |
276 | ||
277 | /** |
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278 | * Finds matching classes within a jar files that contains a folder structure |
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279 | * matching the package structure. If the File is not a JarFile or does not exist a warning |
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280 | * will be logged, but no error will be raised. |
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281 | * |
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282 | * @param test a Test used to filter the classes that are discovered |
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283 | * @param parent the parent package under which classes must be in order to be considered |
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284 | * @param jarfile the jar file to be examined for classes |
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285 | */ |
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286 | private void loadImplementationsInJar(Test test, String parent, File jarfile) { |
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287 | ||
288 | try { |
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289 | JarEntry entry; |
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290 | 0 | JarInputStream jarStream = new JarInputStream(new FileInputStream(jarfile)); |
291 | ||
292 | 0 | while ( (entry = jarStream.getNextJarEntry() ) != null) { |
293 | 0 | String name = entry.getName(); |
294 | 0 | if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) { |
295 | 0 | addIfMatching(test, name); |
296 | } |
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297 | 0 | } |
298 | } |
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299 | 0 | catch (IOException ioe) { |
300 | 0 | log.error("Could not search jar file '" + jarfile + "' for classes matching criteria: " + |
301 | test + "due to an IOException: " + ioe.getMessage()); |
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302 | 0 | } |
303 | 0 | } |
304 | ||
305 | /** |
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306 | * Add the class designated by the fully qualified class name provided to the set of |
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307 | * resolved classes if and only if it is approved by the Test supplied. |
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308 | * |
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309 | * @param test the test used to determine if the class matches |
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310 | * @param fqn the fully qualified name of a class |
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311 | */ |
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312 | protected void addIfMatching(Test test, String fqn) { |
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313 | try { |
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314 | 374 | String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.'); |
315 | 374 | ClassLoader loader = getClassLoader(); |
316 | 374 | log.trace("Checking to see if class " + externalName + " matches criteria [" + test+ "]"); |
317 | ||
318 | 374 | Class type = loader.loadClass(externalName); |
319 | 374 | if (test.matches(type) ) { |
320 | 170 | matches.add( (Class<T>) type); |
321 | } |
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322 | } |
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323 | 0 | catch (Throwable t) { |
324 | 0 | log.warn("Could not examine class '"+ fqn + "' due to a " + |
325 | t.getClass().getName()+ " with message: " + t.getMessage()); |
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326 | 374 | } |
327 | 374 | } |
328 | } |