Use reflection to access the true classpath info. : ClassPath « Reflection « Java

1. Java
2. Reflection
3. ClassPath

Use reflection to access the true classpath info.

 
import java.lang.reflect.Method;
import java.net.URL;
import java.security.CodeSource;
import java.security.ProtectionDomain;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

public class Main {


  /**
   * Format a string buffer containing the Class, Interfaces, CodeSource, and
   * ClassLoader information for the given object clazz.
   * 
   * @param clazz
   *          the Class
   * @param results -
   *          the buffer to write the info to
   */
  public static void displayClassInfo(Class clazz, StringBuffer results) {
    // Print out some codebase info for the clazz
    ClassLoader cl = clazz.getClassLoader();
    results.append("\n");
    results.append(clazz.getName());
    results.append("(");
    results.append(Integer.toHexString(clazz.hashCode()));
    results.append(").ClassLoader=");
    results.append(cl);
    ClassLoader parent = cl;
    while (parent != null) {
      results.append("\n..");
      results.append(parent);
      URL[] urls = getClassLoaderURLs(parent);
      int length = urls != null ? urls.length : 0;
      for (int u = 0; u < length; u++) {
        results.append("\n....");
        results.append(urls[u]);
      }
      if (parent != null)
        parent = parent.getParent();
    }
    CodeSource clazzCS = clazz.getProtectionDomain().getCodeSource();
    if (clazzCS != null) {
      results.append("\n++++CodeSource: ");
      results.append(clazzCS);
    } else
      results.append("\n++++Null CodeSource");

    results.append("\nImplemented Interfaces:");
    Class[] ifaces = clazz.getInterfaces();
    for (int i = 0; i < ifaces.length; i++) {
      Class iface = ifaces[i];
      results.append("\n++");
      results.append(iface);
      results.append("(");
      results.append(Integer.toHexString(iface.hashCode()));
      results.append(")");
      ClassLoader loader = ifaces[i].getClassLoader();
      results.append("\n++++ClassLoader: ");
      results.append(loader);
      ProtectionDomain pd = ifaces[i].getProtectionDomain();
      CodeSource cs = pd.getCodeSource();
      if (cs != null) {
        results.append("\n++++CodeSource: ");
        results.append(cs);
      } else
        results.append("\n++++Null CodeSource");
    }
  }


  /**
   * Use reflection to access a URL[] getURLs or URL[] getClasspath method so
   * that non-URLClassLoader class loaders, or class loaders that override
   * getURLs to return null or empty, can provide the true classpath info.
   * 
   * @param cl
   * @return the urls
   */
  public static URL[] getClassLoaderURLs(ClassLoader cl) {
    URL[] urls = {};
    try {
      Class returnType = urls.getClass();
      Class[] parameterTypes = {};
      Class clClass = cl.getClass();
      Method getURLs = clClass.getMethod("getURLs", parameterTypes);
      if (returnType.isAssignableFrom(getURLs.getReturnType())) {
        Object[] args = {};
        urls = (URL[]) getURLs.invoke(cl, args);
      }
      if (urls == null || urls.length == 0) {
        Method getCp = clClass.getMethod("getClasspath", parameterTypes);
        if (returnType.isAssignableFrom(getCp.getReturnType())) {
          Object[] args = {};
          urls = (URL[]) getCp.invoke(cl, args);
        }
      }
    } catch (Exception ignore) {
    }
    return urls;
  }
}

   
  

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