| Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
| ResolverUtil |
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| 0.0;0 |
| 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one or more |
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| 3 | * contributor license agreements. See the NOTICE file distributed with |
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| 4 | * this work for additional information regarding copyright ownership. |
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| 5 | * The ASF licenses this file to You under the Apache License, Version 2.0 |
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| 6 | * (the "License"); you may not use this file except in compliance with |
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| 7 | * the License. You may obtain a copy of the License at |
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| 8 | * |
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| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 10 | * |
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| 11 | * Unless required by applicable law or agreed to in writing, software |
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| 12 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 14 | * See the License for the specific language governing permissions and |
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| 15 | * limitations under the License. |
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| 16 | */ |
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| 17 | package org.apache.camel.util; |
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| 18 | ||
| 19 | import java.io.File; |
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| 20 | import java.io.FileInputStream; |
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| 21 | import java.io.IOException; |
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| 22 | import java.lang.annotation.Annotation; |
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| 23 | import java.net.URL; |
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| 24 | import java.net.URLDecoder; |
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| 25 | import java.util.Enumeration; |
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| 26 | import java.util.HashSet; |
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| 27 | import java.util.Set; |
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| 28 | import java.util.jar.JarEntry; |
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| 29 | import java.util.jar.JarInputStream; |
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| 30 | ||
| 31 | import org.apache.commons.logging.Log; |
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| 32 | import org.apache.commons.logging.LogFactory; |
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| 33 | ||
| 34 | /** |
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| 35 | * <p> |
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| 36 | * ResolverUtil is used to locate classes that are available in the/a class path |
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| 37 | * and meet arbitrary conditions. The two most common conditions are that a |
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| 38 | * class implements/extends another class, or that is it annotated with a |
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| 39 | * specific annotation. However, through the use of the {@link Test} class it is |
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| 40 | * possible to search using arbitrary conditions. |
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| 41 | * </p> |
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| 42 | * |
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| 43 | * <p> |
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| 44 | * A ClassLoader is used to locate all locations (directories and jar files) in |
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| 45 | * the class path that contain classes within certain packages, and then to load |
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| 46 | * those classes and check them. By default the ClassLoader returned by |
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| 47 | * {@code Thread.currentThread().getContextClassLoader()} is used, but this can |
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| 48 | * be overridden by calling {@link #setClassLoader(ClassLoader)} prior to |
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| 49 | * invoking any of the {@code find()} methods. |
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| 50 | * </p> |
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| 51 | * |
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| 52 | * <p> |
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| 53 | * General searches are initiated by calling the |
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| 54 | * {@link #find(ResolverUtil.Test, String)} ()} method and supplying a package |
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| 55 | * name and a Test instance. This will cause the named package <b>and all |
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| 56 | * sub-packages</b> to be scanned for classes that meet the test. There are |
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| 57 | * also utility methods for the common use cases of scanning multiple packages |
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| 58 | * for extensions of particular classes, or classes annotated with a specific |
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| 59 | * annotation. |
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| 60 | * </p> |
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| 61 | * |
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| 62 | * <p> |
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| 63 | * The standard usage pattern for the ResolverUtil class is as follows: |
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| 64 | * </p> |
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| 65 | * |
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| 66 | * <pre> |
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| 67 | * esolverUtil<ActionBean> resolver = new ResolverUtil<ActionBean>(); |
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| 68 | * esolver.findImplementation(ActionBean.class, pkg1, pkg2); |
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| 69 | * esolver.find(new CustomTest(), pkg1); |
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| 70 | * esolver.find(new CustomTest(), pkg2); |
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| 71 | * ollection<ActionBean> beans = resolver.getClasses(); |
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| 72 | * </pre> |
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| 73 | * |
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| 74 | * @author Tim Fennell |
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| 75 | */ |
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| 76 | 351 | public class ResolverUtil<T> { |
| 77 | 3 | private static final transient Log LOG = LogFactory.getLog(ResolverUtil.class); |
| 78 | ||
| 79 | /** |
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| 80 | * A simple interface that specifies how to test classes to determine if |
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| 81 | * they are to be included in the results produced by the ResolverUtil. |
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| 82 | */ |
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| 83 | public static interface Test { |
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| 84 | /** |
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| 85 | * Will be called repeatedly with candidate classes. Must return True if |
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| 86 | * a class is to be included in the results, false otherwise. |
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| 87 | */ |
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| 88 | boolean matches(Class type); |
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| 89 | } |
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| 90 | ||
| 91 | /** |
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| 92 | * A Test that checks to see if each class is assignable to the provided |
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| 93 | * class. Note that this test will match the parent type itself if it is |
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| 94 | * presented for matching. |
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| 95 | */ |
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| 96 | public static class IsA implements Test { |
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| 97 | private Class parent; |
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| 98 | ||
| 99 | /** |
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| 100 | * Constructs an IsA test using the supplied Class as the parent |
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| 101 | * class/interface. |
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| 102 | */ |
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| 103 | 0 | public IsA(Class parentType) { |
| 104 | 0 | this.parent = parentType; |
| 105 | 0 | } |
| 106 | ||
| 107 | /** |
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| 108 | * Returns true if type is assignable to the parent type supplied in the |
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| 109 | * constructor. |
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| 110 | */ |
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| 111 | public boolean matches(Class type) { |
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| 112 | 0 | return type != null && parent.isAssignableFrom(type); |
| 113 | } |
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| 114 | ||
| 115 | @Override |
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| 116 | public String toString() { |
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| 117 | 0 | return "is assignable to " + parent.getSimpleName(); |
| 118 | } |
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| 119 | } |
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| 120 | ||
| 121 | /** |
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| 122 | * A Test that checks to see if each class is annotated with a specific |
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| 123 | * annotation. If it is, then the test returns true, otherwise false. |
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| 124 | */ |
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| 125 | public static class AnnotatedWith implements Test { |
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| 126 | private Class<? extends Annotation> annotation; |
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| 127 | ||
| 128 | /** Construts an AnnotatedWith test for the specified annotation type. */ |
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| 129 | 141 | public AnnotatedWith(Class<? extends Annotation> annotation) { |
| 130 | 141 | this.annotation = annotation; |
| 131 | 141 | } |
| 132 | ||
| 133 | /** |
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| 134 | * Returns true if the type is annotated with the class provided to the |
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| 135 | * constructor. |
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| 136 | */ |
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| 137 | public boolean matches(Class type) { |
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| 138 | 1551 | return type != null && type.isAnnotationPresent(annotation); |
| 139 | } |
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| 140 | ||
| 141 | @Override |
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| 142 | public String toString() { |
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| 143 | 1833 | return "annotated with @" + annotation.getSimpleName(); |
| 144 | } |
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| 145 | } |
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| 146 | ||
| 147 | /** The set of matches being accumulated. */ |
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| 148 | 351 | private Set<Class<? extends T>> matches = new HashSet<Class<? extends T>>(); |
| 149 | ||
| 150 | /** |
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| 151 | * The ClassLoader to use when looking for classes. If null then the |
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| 152 | * ClassLoader returned by Thread.currentThread().getContextClassLoader() |
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| 153 | * will be used. |
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| 154 | */ |
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| 155 | private ClassLoader classloader; |
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| 156 | ||
| 157 | /** |
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| 158 | * Provides access to the classes discovered so far. If no calls have been |
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| 159 | * made to any of the {@code find()} methods, this set will be empty. |
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| 160 | * |
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| 161 | * @return the set of classes that have been discovered. |
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| 162 | */ |
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| 163 | public Set<Class<? extends T>> getClasses() { |
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| 164 | 141 | return matches; |
| 165 | } |
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| 166 | ||
| 167 | /** |
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| 168 | * Returns the classloader that will be used for scanning for classes. If no |
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| 169 | * explicit ClassLoader has been set by the calling, the context class |
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| 170 | * loader will be used. |
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| 171 | * |
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| 172 | * @return the ClassLoader that will be used to scan for classes |
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| 173 | */ |
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| 174 | public ClassLoader getClassLoader() { |
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| 175 | 1692 | return classloader == null ? Thread.currentThread().getContextClassLoader() : classloader; |
| 176 | } |
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| 177 | ||
| 178 | /** |
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| 179 | * Sets an explicit ClassLoader that should be used when scanning for |
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| 180 | * classes. If none is set then the context classloader will be used. |
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| 181 | * |
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| 182 | * @param classloader a ClassLoader to use when scanning for classes |
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| 183 | */ |
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| 184 | public void setClassLoader(ClassLoader classloader) { |
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| 185 | 0 | this.classloader = classloader; |
| 186 | 0 | } |
| 187 | ||
| 188 | /** |
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| 189 | * Attempts to discover classes that are assignable to the type provided. In |
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| 190 | * the case that an interface is provided this method will collect |
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| 191 | * implementations. In the case of a non-interface class, subclasses will be |
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| 192 | * collected. Accumulated classes can be accessed by calling |
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| 193 | * {@link #getClasses()}. |
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| 194 | * |
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| 195 | * @param parent the class of interface to find subclasses or |
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| 196 | * implementations of |
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| 197 | * @param packageNames one or more package names to scan (including |
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| 198 | * subpackages) for classes |
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| 199 | */ |
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| 200 | public void findImplementations(Class parent, String... packageNames) { |
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| 201 | 0 | if (packageNames == null) { |
| 202 | 0 | return; |
| 203 | } |
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| 204 | ||
| 205 | 0 | Test test = new IsA(parent); |
| 206 | 0 | for (String pkg : packageNames) { |
| 207 | 0 | find(test, pkg); |
| 208 | } |
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| 209 | 0 | } |
| 210 | ||
| 211 | /** |
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| 212 | * Attempts to discover classes that are annotated with to the annotation. |
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| 213 | * Accumulated classes can be accessed by calling {@link #getClasses()}. |
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| 214 | * |
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| 215 | * @param annotation the annotation that should be present on matching |
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| 216 | * classes |
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| 217 | * @param packageNames one or more package names to scan (including |
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| 218 | * subpackages) for classes |
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| 219 | */ |
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| 220 | public void findAnnotated(Class<? extends Annotation> annotation, String... packageNames) { |
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| 221 | 141 | if (packageNames == null) { |
| 222 | 0 | return; |
| 223 | } |
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| 224 | ||
| 225 | 141 | Test test = new AnnotatedWith(annotation); |
| 226 | 282 | for (String pkg : packageNames) { |
| 227 | 141 | find(test, pkg); |
| 228 | } |
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| 229 | 141 | } |
| 230 | ||
| 231 | /** |
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| 232 | * Scans for classes starting at the package provided and descending into |
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| 233 | * subpackages. Each class is offered up to the Test as it is discovered, |
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| 234 | * and if the Test returns true the class is retained. Accumulated classes |
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| 235 | * can be fetched by calling {@link #getClasses()}. |
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| 236 | * |
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| 237 | * @param test an instance of {@link Test} that will be used to filter |
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| 238 | * classes |
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| 239 | * @param packageName the name of the package from which to start scanning |
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| 240 | * for classes, e.g. {@code net.sourceforge.stripes} |
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| 241 | */ |
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| 242 | public void find(Test test, String packageName) { |
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| 243 | 141 | packageName = packageName.replace('.', '/'); |
| 244 | 141 | ClassLoader loader = getClassLoader(); |
| 245 | Enumeration<URL> urls; |
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| 246 | ||
| 247 | try { |
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| 248 | 141 | urls = loader.getResources(packageName); |
| 249 | 0 | } catch (IOException ioe) { |
| 250 | 0 | LOG.warn("Could not read package: " + packageName, ioe); |
| 251 | 0 | return; |
| 252 | 141 | } |
| 253 | ||
| 254 | 423 | while (urls.hasMoreElements()) { |
| 255 | try { |
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| 256 | 282 | String urlPath = urls.nextElement().getFile(); |
| 257 | 282 | urlPath = URLDecoder.decode(urlPath, "UTF-8"); |
| 258 | ||
| 259 | // If it's a file in a directory, trim the stupid file: spec |
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| 260 | 282 | if (urlPath.startsWith("file:")) { |
| 261 | 0 | urlPath = urlPath.substring(5); |
| 262 | } |
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| 263 | ||
| 264 | // Else it's in a JAR, grab the path to the jar |
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| 265 | 282 | if (urlPath.indexOf('!') > 0) { |
| 266 | 0 | urlPath = urlPath.substring(0, urlPath.indexOf('!')); |
| 267 | } |
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| 268 | ||
| 269 | 282 | LOG.debug("Scanning for classes in [" + urlPath + "] matching criteria: " + test); |
| 270 | 282 | File file = new File(urlPath); |
| 271 | 282 | if (file.isDirectory()) { |
| 272 | 282 | loadImplementationsInDirectory(test, packageName, file); |
| 273 | 282 | } else { |
| 274 | 0 | loadImplementationsInJar(test, packageName, file); |
| 275 | } |
|
| 276 | 0 | } catch (IOException ioe) { |
| 277 | 0 | LOG.warn("could not read entries", ioe); |
| 278 | 282 | } |
| 279 | 0 | } |
| 280 | 141 | } |
| 281 | ||
| 282 | /** |
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| 283 | * Finds matches in a physical directory on a filesystem. Examines all files |
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| 284 | * within a directory - if the File object is not a directory, and ends with |
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| 285 | * <i>.class</i> the file is loaded and tested to see if it is acceptable |
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| 286 | * according to the Test. Operates recursively to find classes within a |
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| 287 | * folder structure matching the package structure. |
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| 288 | * |
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| 289 | * @param test a Test used to filter the classes that are discovered |
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| 290 | * @param parent the package name up to this directory in the package |
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| 291 | * hierarchy. E.g. if /classes is in the classpath and we |
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| 292 | * wish to examine files in /classes/org/apache then the |
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| 293 | * values of <i>parent</i> would be <i>org/apache</i> |
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| 294 | * @param location a File object representing a directory |
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| 295 | */ |
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| 296 | private void loadImplementationsInDirectory(Test test, String parent, File location) { |
|
| 297 | 423 | File[] files = location.listFiles(); |
| 298 | 423 | StringBuilder builder = null; |
| 299 | ||
| 300 | 2256 | for (File file : files) { |
| 301 | 1833 | builder = new StringBuilder(100); |
| 302 | 1833 | builder.append(parent).append("/").append(file.getName()); |
| 303 | 1833 | String packageOrClass = parent == null ? file.getName() : builder.toString(); |
| 304 | ||
| 305 | 1833 | if (file.isDirectory()) { |
| 306 | 141 | loadImplementationsInDirectory(test, packageOrClass, file); |
| 307 | 141 | } else if (file.getName().endsWith(".class")) { |
| 308 | 1551 | addIfMatching(test, packageOrClass); |
| 309 | } |
|
| 310 | } |
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| 311 | 423 | } |
| 312 | ||
| 313 | /** |
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| 314 | * Finds matching classes within a jar files that contains a folder |
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| 315 | * structure matching the package structure. If the File is not a JarFile or |
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| 316 | * does not exist a warning will be logged, but no error will be raised. |
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| 317 | * |
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| 318 | * @param test a Test used to filter the classes that are discovered |
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| 319 | * @param parent the parent package under which classes must be in order to |
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| 320 | * be considered |
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| 321 | * @param jarfile the jar file to be examined for classes |
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| 322 | */ |
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| 323 | private void loadImplementationsInJar(Test test, String parent, File jarfile) { |
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| 324 | ||
| 325 | try { |
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| 326 | JarEntry entry; |
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| 327 | 0 | JarInputStream jarStream = new JarInputStream(new FileInputStream(jarfile)); |
| 328 | ||
| 329 | 0 | while ((entry = jarStream.getNextJarEntry()) != null) { |
| 330 | 0 | String name = entry.getName(); |
| 331 | 0 | if (!entry.isDirectory() && name.startsWith(parent) && name.endsWith(".class")) { |
| 332 | 0 | addIfMatching(test, name); |
| 333 | } |
|
| 334 | 0 | } |
| 335 | 0 | } catch (IOException ioe) { |
| 336 | 0 | LOG.error("Could not search jar file '" + jarfile + "' for classes matching criteria: " + test |
| 337 | + "due to an IOException: " + ioe.getMessage()); |
|
| 338 | 0 | } |
| 339 | 0 | } |
| 340 | ||
| 341 | /** |
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| 342 | * Add the class designated by the fully qualified class name provided to |
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| 343 | * the set of resolved classes if and only if it is approved by the Test |
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| 344 | * supplied. |
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| 345 | * |
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| 346 | * @param test the test used to determine if the class matches |
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| 347 | * @param fqn the fully qualified name of a class |
|
| 348 | */ |
|
| 349 | protected void addIfMatching(Test test, String fqn) { |
|
| 350 | try { |
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| 351 | 1551 | String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.'); |
| 352 | 1551 | ClassLoader loader = getClassLoader(); |
| 353 | 1551 | LOG.trace("Checking to see if class " + externalName + " matches criteria [" + test + "]"); |
| 354 | ||
| 355 | 1551 | Class type = loader.loadClass(externalName); |
| 356 | 1551 | if (test.matches(type)) { |
| 357 | 705 | matches.add((Class<T>)type); |
| 358 | } |
|
| 359 | 0 | } catch (Throwable t) { |
| 360 | 0 | LOG.warn("Could not examine class '" + fqn + "' due to a " + t.getClass().getName() |
| 361 | + " with message: " + t.getMessage()); |
|
| 362 | 1551 | } |
| 363 | 1551 | } |
| 364 | } |