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