cvs commit: jakarta-log4j/src/java/org/apache/log4j/chainsaw/help HelpLocator.java

[ps...@apache.org]

psmith      2003/12/21 23:56:34

  Added:       src/java/org/apache/log4j/chainsaw/help HelpLocator.java
  Log:
  added a HelpLocator class to assist in locating help resources.
  
  Revision  Changes    Path
  1.1                  jakarta-log4j/src/java/org/apache/log4j/chainsaw/help/HelpLocator.java
  
  Index: HelpLocator.java
  ===================================================================
  /*
   * ============================================================================
   * The Apache Software License, Version 1.1
   * ============================================================================
   * 
   * Copyright (C) 1999 The Apache Software Foundation. All rights reserved.
   * 
   * Redistribution and use in source and binary forms, with or without modifica-
   * tion, are permitted provided that the following conditions are met: 1.
   * Redistributions of source code must retain the above copyright notice, this
   * list of conditions and the following disclaimer. 2. Redistributions in
   * binary form must reproduce the above copyright notice, this list of
   * conditions and the following disclaimer in the documentation and/or other
   * materials provided with the distribution. 3. The end-user documentation
   * included with the redistribution, if any, must include the following
   * acknowledgment: "This product includes software developed by the Apache
   * Software Foundation (http://www.apache.org/)." Alternately, this
   * acknowledgment may appear in the software itself, if and wherever such
   * third-party acknowledgments normally appear. 4. The names "log4j" and
   * "Apache Software Foundation" must not be used to endorse or promote products
   * derived from this software without prior written permission. For written
   * permission, please contact apache@apache.org. 5. Products derived from this
   * software may not be called "Apache", nor may "Apache" appear in their name,
   * without prior written permission of the Apache Software Foundation.
   * 
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
   * DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
   * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   * 
   * This software consists of voluntary contributions made by many individuals
   * on behalf of the Apache Software Foundation. For more information on the
   * Apache Software Foundation, please see <http://www.apache.org/> .
   *  
   */
  
  package org.apache.log4j.chainsaw.help;
  
  import org.apache.log4j.chainsaw.messages.MessageCenter;
  
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.net.URLClassLoader;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   * A helper class that assists the HelpManager by serving as a collection of
   * Class loaders based on URL roots.
   * 
   * @author Paul Smith
   *         <ps...@apache.org>
   */
  class HelpLocator {
    private List classLoaders = new ArrayList();
  
    HelpLocator() {
    }
  
    /**
     * Adds a ClassLoader to be used as a help resource locator
     */
    void installClassloaderLocator(ClassLoader cl) {
      classLoaders.add(cl);
    }
    /**
     * Adds a new locator to the current set of locators by using the passed in
     * URL as a base to locate help resources. The URL SHOULD end in a '/'
     * character.
     */
    void installLocator(URL url) {
      try {
        classLoaders.add(new HelpResourceLoader(url));
      } catch (Exception e) {
        MessageCenter.getInstance().getLogger().error(
          "Failed to setup the resoure loaders for the Help Subsystem");
      }
    }
  
    /**
     * Locates a help resource by using the internal resource locator collection.
     * 
     * @return URL of the located resource, or null if it cannot be located.
     */
    URL findResource(String name) {
      URL url = null;
  
      for (Iterator iter = classLoaders.iterator(); iter.hasNext();) {
        ClassLoader loader = (ClassLoader) iter.next();
        url = loader.getResource(name);
  
        if (url != null) {
          break;
        }
      }
  
      return url;
    }
  
    private static class HelpResourceLoader extends ClassLoader {
      private URL root;
  
      private HelpResourceLoader(URL root) {
        this.root = root;
      }
  
      /*
       * (non-Javadoc)
       * 
       * @see java.lang.ClassLoader#findResource(java.lang.String)
       */
      protected URL findResource(String name) {
        URL url = super.findResource(name);
  
        if (url != null) {
          return url;
        }
  
        try {
          URL resourceURL = new URL(root, name);
  
          return new URLClassLoader(
            new URL[] { root, resourceURL }).findResource(
            name);
        } catch (MalformedURLException e) {
          e.printStackTrace();
        }
  
        return null;
      }
    }
  
    //  public static void main(String[] args) throws Exception {
    //    HelpLocator locator = new HelpLocator();
    //    locator.installLocator(new File(".").toURL());
    //    locator.installLocator(new
    // URL("http://java.sun.com/j2se/1.4.2/docs/api/"));
    //    String[] resources =
    //      new String[] { "build.properties", "java/lang/ClassLoader.html", };
    //
    //    for (int i = 0; i < resources.length; i++) {
    //      String resource = resources[i];
    //      URL url = locator.findResource(resource);
    //      System.out.println("resource=" + resource + ", url=" + url);
    //    }
    //  }
  }
  
  
  

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