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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17  package org.apache.log4j.chainsaw.plugins;
    18
    19  import org.apache.log4j.chainsaw.prefs.SettingsManager;
    20
    21  import java.io.File;
    22  import java.net.URL;
    23  import java.net.URLClassLoader;
    24  import java.util.ArrayList;
    25  import java.util.List;
    26
    27  /**
    28   * A factory class to create a Classloader that can refenerence jars/classes/resources
    29   * within a users plugin directory.
    30   * <p>
    31   * Currently a work in progress to see if this allows external jars required by
    32   * some 3rd party vendors for things like the JMSReceiver.
    33   *
    34   * @author psmith
    35   */
    36  public class PluginClassLoaderFactory {
    37      private final ClassLoader pluginClassLoader;
    38
    39      private static final PluginClassLoaderFactory instance = new PluginClassLoaderFactory();
    40
    41      private PluginClassLoaderFactory() {
    42          this.pluginClassLoader = PluginClassLoaderFactory.create(new File(SettingsManager.getInstance().getSettingsDirectory() + File.separator + "plugins"));
    43
    44      }
    45
    46      public static PluginClassLoaderFactory getInstance() {
    47          return instance;
    48      }
    49
    50      public ClassLoader getClassLoader() {
    51          return this.pluginClassLoader;
    52      }
    53
    54      /**
    55       * Creates a Classloader that will be able to access any of the classes found
    56       * in any .JAR file contained within the specified directory path, PLUS
    57       * the actual Plugin directory itself, so it acts like the WEB-INF/classes directory,
    58       * any class file in the directory will be accessible
    59       *
    60       * @param pluginDirectory
    61       * @return
    62       * @throws IllegalArgumentException if the pluginDirectory is null, does not exist, or cannot be read
    63       * @throws RuntimeException         if turning a File into a URL failed, which would be very unexpected
    64       */
    65      private static final ClassLoader create(File pluginDirectory) {
    66          if (pluginDirectory == null || !pluginDirectory.exists() || !pluginDirectory.canRead()) {
    67              return PluginClassLoaderFactory.class.getClassLoader();
    68          }
    69
    70          String[] strings = pluginDirectory.list((dir, name) -> name.toUpperCase().endsWith(".JAR"));
    71
    72
    73          List<URL> list = new ArrayList<>();
    74          // add the plugin directory as a resource loading path
    75          try {
    76              list.add(pluginDirectory.toURI().toURL());
    77          } catch (Exception e) {
    78              throw new RuntimeException(e.getMessage());
    79          }
    80          if (strings != null) {
    81              for (String name : strings) {
    82                  File file = new File(pluginDirectory, name);
    83                  try {
    84                      list.add(file.toURI().toURL());
    85                      System.out.println("Added " + file.getAbsolutePath()
    86                          + " to Plugin class loader list");
    87                  } catch (Exception e) {
    88                      System.err.println("Failed to retrieve the URL for file: "
    89                          + file.getAbsolutePath());
    90                      throw new RuntimeException(e.getMessage());
    91                  }
    92              }
    93          }
    94          ClassLoader parent = PluginClassLoaderFactory.class.getClassLoader();
    95          URL[] urls = (URL[]) list.toArray(new URL[list.size()]);
    96          return new URLClassLoader(urls, parent);
    97      }
    98
    99  }