bundles/org.eclipse.core.boot/src/org/eclipse/core/internal/boot/DelegatingURLClassLoader.java - gerrit/platform/eclipse.platform.runtime - Git at Google

 package org.eclipse.core.internal.boot;

 /*
  * Licensed Materials - Property of IBM,
  * WebSphere Studio Workbench
  * (c) Copyright IBM Corp 2000
  */
 import java.net.*;
 import java.util.*;
 import java.io.*;
 import java.security.CodeSource;
 import java.security.ProtectionDomain;
 import org.eclipse.core.boot.BootLoader;

 public abstract class DelegatingURLClassLoader extends URLClassLoader {

 	// loader base
 	protected URL base;

 	// delegation chain
 	protected DelegateLoader[] imports = null;

 	// extra resource class loader
 	protected URLClassLoader resourceLoader = null;

 	// filter table
 	private Hashtable filterTable = new Hashtable();

 	// development mode class path additions
 	public static String devClassPath = null;
 	// native library loading
 	private static String libPrefix;
 	private static String libSuffix;
 	private static final String WIN_LIBRARY_PREFIX = "";
 	private static final String WIN_LIBRARY_SUFFIX = ".dll";
 	private static final String UNIX_LIBRARY_PREFIX = "lib";
 	private static final String UNIX_LIBRARY_SUFFIX = ".so";
 	private Hashtable nativeLibs = new Hashtable();
 	private static final int BUF_SIZE = 32768;

 	// control class load tracing
 	public static boolean DEBUG = false;
 	public static boolean DEBUG_SHOW_CREATE = true;
 	public static boolean DEBUG_SHOW_ACTIVATE = true;
 	public static boolean DEBUG_SHOW_ACTIONS = true;
 	public static boolean DEBUG_SHOW_SUCCESS = true;
 	public static boolean DEBUG_SHOW_FAILURE = true;
 	public static String[] DEBUG_FILTER_CLASS = new String[0];
 	public static String[] DEBUG_FILTER_LOADER = new String[0];
 	public static String[] DEBUG_FILTER_RESOURCE = new String[0];
 	public static String[] DEBUG_FILTER_NATIVE = new String[0];

 	// DelegateLoader. Represents a single class loader this loader delegates to.
 	protected static class DelegateLoader {

 		private DelegatingURLClassLoader loader;
 		private boolean isExported;

 		public DelegateLoader(DelegatingURLClassLoader loader, boolean isExported) {
 			this.loader = loader;
 			this.isExported = isExported;
 		}

 		public Class loadClass(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
 			if (isExported || current == requestor)
 				return loader.loadClass(name, false, requestor, seen, false);
 			else
 				return null;
 		}

 		public URL findResource(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
 			if (isExported || current == requestor)
 				return loader.findResource(name, requestor, seen);
 			else
 				return null;
 		}
 		public Enumeration findResources(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
 			if (isExported || current == requestor)
 				return loader.findResources(name, requestor, seen);
 			else
 				return null;
 		}
 	}

 	// unchecked DelegatingLoaderException
 	protected static class DelegatingLoaderException extends RuntimeException {
 		Exception e = null;

 		public DelegatingLoaderException() {
 			super();
 		}

 		public DelegatingLoaderException(String message) {
 			super(message);
 		}

 		public DelegatingLoaderException(String message, Exception e) {
 			super(message);
 			this.e = e;
 		}

 		public Throwable getException() {
 			return e;
 		}
 	}

 public DelegatingURLClassLoader(URL[] codePath, URLContentFilter[] codeFilters, URL[] resourcePath, URLContentFilter[] resourceFilters, ClassLoader parent) {
 	super(codePath, parent);
 	initialize();
 	if (resourcePath != null)
 		resourceLoader = new ResourceLoader(resourcePath);

 	if (codePath != null) {
 		if (codeFilters == null || codeFilters.length != codePath.length)
 			throw new DelegatingLoaderException();
 		for (int i = 0; i < codePath.length; i++) {
 			if (codeFilters[i] != null)
 				filterTable.put(codePath[i], codeFilters[i]);
 		}
 	}
 	if (resourcePath != null) {
 		if (resourceFilters == null || resourceFilters.length != resourcePath.length)
 			throw new DelegatingLoaderException();
 		for (int i = 0; i < resourcePath.length; i++) {
 			if (resourceFilters[i] != null)
 				filterTable.put(resourcePath[i], resourceFilters[i]);
 		}
 	}
 }
 /**
  * Returns the given class or <code>null</code> if the class is not visible to the
  * given requestor.  The <code>inCache</code> flag controls how this action is
  * reported if in debug mode.
  */
 protected Class checkClassVisibility(Class result, DelegatingURLClassLoader requestor, boolean inCache) {
 	if (result == null)
 		return null;
 	if (isClassVisible(result, requestor)) {
 		if (DEBUG && DEBUG_SHOW_SUCCESS && debugClass(result.getName()))
 			debug("found " + result.getName() + " in " + (inCache ? "cache" : getURLforClass(result).toExternalForm()));
 	} else {
 		if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(result.getName()))
 			debug("skip " + result.getName() + " in " + (inCache ? "cache" : getURLforClass(result).toExternalForm()));
 		return null;
 	}
 	return result;
 }
 /**
  * Returns the given resource URL or <code>null</code> if the resource is not visible to the
  * given requestor.
  */
 protected URL checkResourceVisibility(String name, URL result, DelegatingURLClassLoader requestor) {
 	if (result == null)
 		return null;
 	if (isResourceVisible(name, result, requestor)) {
 		if (DEBUG && DEBUG_SHOW_SUCCESS && debugResource(name))
 			debug("found " + result);
 	} else {
 		if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
 			debug("skip " + result);
 		result = null;
 	}
 	return result;
 }
 protected void debug(String s) {

 	System.out.println(toString()+"^"+Integer.toHexString(Thread.currentThread().hashCode())+" "+s);
 }
 protected boolean debugClass(String name) {

 	if (debugLoader()) {
 		return debugMatchesFilter(name,DEBUG_FILTER_CLASS);
 	}
 	return false;
 }
 protected void debugConstruction() {
 	if (DEBUG && DEBUG_SHOW_CREATE && debugLoader()) {
 		URL[] urls = getURLs();
 		debug("Class Loader Created");
 		debug("> baseURL=" + base);
 		if (urls == null || urls.length == 0)
 			debug("> empty search path");
 		else {
 			URLContentFilter filter;
 			for (int i = 0; i < urls.length; i++) {
 				debug("> searchURL=" + urls[i].toString());
 				filter = (URLContentFilter) filterTable.get(urls[i]);
 				if (filter != null)
 					debug(">    export=" + filter.toString());
 			}
 		}
 	}
 }
 protected String debugId() {
 	return "";
 }
 protected boolean debugLoader() {

 	return debugMatchesFilter(debugId(),DEBUG_FILTER_LOADER);
 }
 private boolean debugMatchesFilter(String name, String[] filter) {

 	if (filter.length==0) return false;

 	for (int i=0; i<filter.length; i++) {
 		if (filter[i].equals("*")) return true;
 		if (name.startsWith(filter[i])) return true;
 	}
 	return false;
 }
 protected boolean debugNative(String name) {

 	if (debugLoader()) {
 		return debugMatchesFilter(name,DEBUG_FILTER_NATIVE);
 	}
 	return false;
 }
 protected boolean debugResource(String name) {

 	if (debugLoader()) {
 		return debugMatchesFilter(name,DEBUG_FILTER_RESOURCE);
 	}
 	return false;
 }
 /**
  * Looks for the requested class in the parent of this loader using
  * standard Java protocols.  If the parent is null then the system class
  * loader is consulted.  <code>null</code> is returned if the class could
  * not be found.
  */
 protected Class findClassParents(String name, boolean resolve) {
 	try {
 		ClassLoader parent = getParent();
 		if (parent == null)
 			return findSystemClass(name);
 		return parent.loadClass(name);
 	} catch (ClassNotFoundException e) {
 	}
 	return null;
 }
 /**
  * Finds and loads the class with the specified name from the URL search
  * path. Any URLs referring to JAR files are loaded and opened as needed
  * until the class is found.   Search on the parent chain and then self.
  *
  * Subclasses should implement this method.
  *
  * @param name the name of the class
  * @param resolve whether or not to resolve the class if found
  * @param requestor class loader originating the request
  * @param checkParents whether the parent of this loader should be consulted
  * @return the resulting class
  */
 protected abstract Class findClassParentsSelf(final String name, boolean resolve, DelegatingURLClassLoader requestor, boolean checkParents);
 /**
  * Finds and loads the class with the specified name from the URL search
  * path. Any URLs referring to JAR files are loaded and opened as needed
  * until the class is found.  This method consults only the platform class loader.
  *
  * @param name the name of the class
  * @param resolve whether or not to resolve the class if found
  * @param requestor class loader originating the request
  * @param checkParents whether the parent of this loader should be consulted
  * @return the resulting class
  */
 protected Class findClassPlatform(String name, boolean resolve, DelegatingURLClassLoader requestor, boolean checkParents) {
 	DelegatingURLClassLoader platform = PlatformClassLoader.getDefault();
 	if (this == platform)
 		return null;
 	return platform.findClassParentsSelf(name, resolve, requestor, false);
 }
 /**
  * Finds and loads the class with the specified name from the URL search
  * path. Any URLs referring to JAR files are loaded and opened as needed
  * until the class is found.  This method considers only the classes loadable
  * by its explicit prerequisite loaders.
  *
  * @param name the name of the class
  * @param requestor class loader originating the request
  * @param seen list of delegated class loaders already searched
  * @return the resulting class
  */
 protected Class findClassPrerequisites(final String name, DelegatingURLClassLoader requestor, Vector seen) {
 	if (imports == null)
 		return null;
 	if (seen == null)
 		seen = new Vector(); // guard against delegation loops
 	seen.addElement(this);
 	// Grab onto the imports value to protect against concurrent write.
 	DelegateLoader[] loaders = imports;
 	for (int i = 0; i < loaders.length; i++) {
 		Class result = loaders[i].loadClass(name, this, requestor, seen);
 		if (result != null)
 			return result;
 	}
 	return null;
 }
 /**
  * Finds the resource with the specified name on the URL search path.
  * This method is used specifically to find the file containing a class to verify
  * that the class exists without having to load it.
  * Returns a URL for the resource.  Searches only this loader's classpath.
  * <code>null</code> is returned if the resource cannot be found.
  *
  * @param name the name of the resource
  */
 protected URL findClassResource(String name) {
 	return super.findResource(name);
 }
 /**
  * Returns the absolute path name of a native library. The VM
  * invokes this method to locate the native libraries that belong
  * to classes loaded with this class loader. If this method returns
  * <code>null</code>, the VM searches the library along the path
  * specified as the <code>java.library.path</code> property.
  *
  * @param      libname   the library name
  * @return     the absolute path of the native library
  */
 protected String findLibrary(String libname) {
 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugNative(libname))
 		debug("findLibrary(" + libname + ")");

 	if (base == null)
 		return null;
 	File libFile = null;
 	String osLibFileName = libPrefix + libname + libSuffix;
 	if (base.getProtocol().equals(PlatformURLHandler.FILE) || base.getProtocol().equals(PlatformURLHandler.VA)) {
 		// directly access library
 		String libFileName = (base.getFile() + osLibFileName).replace('/', File.separatorChar);
 		libFile = new File(libFileName);
 	} else
 		if (base.getProtocol().equals(PlatformURLHandler.PROTOCOL))
 			// access library through eclipse URL
 			libFile = getNativeLibraryAsLocal(osLibFileName);

 	if (libFile == null)
 		return null;
 	if (!libFile.exists()) {
 		if (DEBUG && DEBUG_SHOW_FAILURE && debugNative(libname))
 			debug("not found " + libname);
 		return null; // can't find the file
 	}

 	if (DEBUG && DEBUG_SHOW_SUCCESS && debugNative(libname))
 		debug("found " + libname + " as " + libFile.getAbsolutePath());

 	return libFile.getAbsolutePath();
 }
 /**
  * Finds the resource with the specified name on the URL search path.
  * Returns a URL for the resource. If resource is not found in own
  * URL search path, delegates search to prerequisite loaders.
  * Null is returned if none of the loaders find the resource.
  *
  * @param name the name of the resource
  */
 public URL findResource(String name) {
 	return findResource(name, this, null);
 }
 /**
  * Delegated resource access call.
  * Does not check prerequisite loader parent chain.
  */
 protected URL findResource(String name, DelegatingURLClassLoader requestor, Vector seen) {
 	// guard against delegation loops
 	if (seen != null && seen.contains(this))
 		return null;

 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
 		debug("findResource(" + name + ")");

 	// check the normal class path for self
 	URL result = super.findResource(name);
 	result = checkResourceVisibility(name, result, requestor);
 	if (result != null)
 		return result;

 	// check our extra resource path if any
 	if (resourceLoader != null) {
 		result = resourceLoader.findResource(name);
 		result = checkResourceVisibility(name, result, requestor);
 		if (result != null)
 			return result;
 	}

 	// delegate down the prerequisite chain if we haven't found anything yet.
 	if (imports != null) {
 		if (seen == null)
 			seen = new Vector(); // guard against delegation loops
 		seen.addElement(this);
 		for (int i = 0; i < imports.length && result == null; i++)
 			result = imports[i].findResource(name, this, requestor, seen);
 	}
 	return result;
 }
 /**
  * Returns an Enumeration of URLs representing all of the resources
  * on the URL search path having the specified name.
  *
  * @param name the resource name
  */
 public Enumeration findResources(String name) throws IOException {
 	return findResources(name, this, null);
 }
 /**
  * Delegated call to locate all named resources.
  * Does not check prerequisite loader parent chain.
  */
 private Enumeration findResources(String name, DelegatingURLClassLoader requestor, Vector seen) {
 	// guard against delegation loops
 	if (seen != null && seen.contains(this))
 		return null;

 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
 		debug("findResources(" + name + ")");

 	// check own URL search path
 	Enumeration e = null;
 	try {
 		e = super.findResources(name);
 	} catch (IOException ioe) {
 	}
 	ResourceEnumeration result = new ResourceEnumeration(name, e, this, requestor);

 	// delegate down the prerequisite chain
 	if (imports != null) {
 		if (seen == null)
 			seen = new Vector(); // guard against delegation loops
 		seen.addElement(this);
 		for (int i = 0; i < imports.length; i++)
 			result.add(imports[i].findResources(name, this, requestor, seen));
 	}

 	return result;
 }
 private File getNativeLibraryAsLocal(String osname) {
 	File result = null;
 	try {
 		URL liburl = new URL(base, osname);
 		PlatformURLConnection c = (PlatformURLConnection) liburl.openConnection();
 		URL localName = c.getURLAsLocal();
 		result = new File(localName.getFile());
 	} catch (IOException e) {
 	}
 	return result;
 }
 public URL getResource(String name) {
 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
 		debug("getResource(" + name + ")");

 	URL result = super.getResource(name);
 	if (result == null) {
 		if (DEBUG && DEBUG_SHOW_FAILURE && debugResource(name))
 			debug("not found " + name);
 	}
 	return result;
 }
 private URL getURLforClass(Class clazz) {
 	ProtectionDomain pd = clazz.getProtectionDomain();
 	if (pd != null) {
 		CodeSource cs = pd.getCodeSource();
 		if (cs != null)
 			return cs.getLocation();
 	}
 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(clazz.getName()))
 		debug("*** " + clazz.getName());
 	return null;
 }
 private void initialize() {
 	if (BootLoader.getOS().equals(BootLoader.OS_WIN32)) {
 		libPrefix = WIN_LIBRARY_PREFIX;
 		libSuffix = WIN_LIBRARY_SUFFIX;
 	} else {
 		libPrefix = UNIX_LIBRARY_PREFIX;
 		libSuffix = UNIX_LIBRARY_SUFFIX;
 	}
 }
 public void initializeImportedLoaders() {
 }
 /**
  * check to see if class is visible (exported)
  */
 boolean isClassVisible(Class clazz, DelegatingURLClassLoader requestor) {
 	URL lib = getURLforClass(clazz);
 	if (lib == null)
 		return true; // have a system class (see comment below)

 	URLContentFilter filter = (URLContentFilter) filterTable.get(lib);
 	if (filter == null) {
 		// This code path is being executed because some VMs (eg. Sun JVM)
 		// return from the class cache classes that were not loaded
 		// by this class loader. Consequently we do not find the
 		// corresponding jar filter. This appears to be a performance
 		// optimization that we are defeating with our filtering scheme.
 		// We return the class if it is a system class (see above). Otherwise
 		// we reject the class which caused the load to be
 		// delegated down the prerequisite chain until we find the
 		// correct loader.
 		if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(clazz.getName()))
 			debug("*** Unable to find library filter for " + clazz.getName() + " from " + lib);
 		return false;
 	} else
 		return filter.isClassVisible(clazz, this, requestor);
 }
 /**
  * check to see if resource is visible (exported)
  */
 boolean isResourceVisible(String name, URL resource, DelegatingURLClassLoader requestor) {
 	URL lib = null;
 	String file = resource.getFile();
 	try {
 		lib = new URL(resource.getProtocol(), resource.getHost(), file.substring(0, file.length() - name.length()));
 	} catch (MalformedURLException e) {
 		if (DEBUG)
 			debug("Unable to determine resource lib for " + name + " from " + resource);
 		return false;
 	}

 	URLContentFilter filter = (URLContentFilter) filterTable.get(lib);
 	if (filter == null) {
 		if (DEBUG)
 			debug("Unable to find library filter for " + name + " from " + lib);
 		return false;
 	} else
 		return filter.isResourceVisible(name, this, requestor);
 }
 /**
  * Non-delegated load call.  This method is not synchronized.  Implementations of
  * findClassParentsSelf, and perhaps others, should synchronize themselves as
  * required.  Synchronizing this method is too coarse-grained.   It results in plugin
  * activation being synchronized and may cause deadlock.
  */
 protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
 	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(name))
 		debug("loadClass(" + name + ")");
 	Class result = loadClass(name, resolve, this, null, true);
 	if (result == null) {
 		if (DEBUG && DEBUG_SHOW_FAILURE && debugClass(name))
 			debug("not found " + name);
 		throw new ClassNotFoundException(name);
 	}
 	return result;
 }
 /**
  * Delegated load call.  This method is not synchronized.  Implementations of
  * findClassParentsSelf, and perhaps others, should synchronize themselves as
  * required.  Synchronizing this method is too coarse-grained.   It results in plugin
  * activation being synchronized and may cause deadlock.
  */
 private Class loadClass(String name, boolean resolve, DelegatingURLClassLoader requestor, Vector seen, boolean checkParents) {
 	// guard against delegation loops
 	if (seen != null && seen.contains(this))
 		return null;

 	// look in the parents and self
 	Class result = findClassParentsSelf(name, resolve, requestor, checkParents);

 	// search platform
 	if (result == null)
 		result = findClassPlatform(name, resolve, requestor, false);

 	// search prerequisites
 	if (result == null)
 		result = findClassPrerequisites(name, requestor, seen);

 	// if we found a class, consider resolving it
 	if (result != null && resolve)
 		resolveClass(result);

 	return result;
 }
 protected void setImportedLoaders(DelegateLoader[] loaders) {

 	imports = loaders;

 	if(DEBUG && DEBUG_SHOW_CREATE && debugLoader()) {
 		debug("Imports");
 		if (imports==null || imports.length==0) debug("> none");
 		else {
 			for (int i=0; i<imports.length; i++) {
 				debug("> " + imports[i].loader.toString() + " export=" + imports[i].isExported);
 			}
 		}
 	}
 }
 public String toString() {
 	return "Loader [" + debugId() + "]";
 }
 }
	package org.eclipse.core.internal.boot;

	/*
	* Licensed Materials - Property of IBM,
	* WebSphere Studio Workbench
	* (c) Copyright IBM Corp 2000
	*/
	import java.net.*;
	import java.util.*;
	import java.io.*;
	import java.security.CodeSource;
	import java.security.ProtectionDomain;
	import org.eclipse.core.boot.BootLoader;

	public abstract class DelegatingURLClassLoader extends URLClassLoader {

	// loader base
	protected URL base;

	// delegation chain
	protected DelegateLoader[] imports = null;

	// extra resource class loader
	protected URLClassLoader resourceLoader = null;

	// filter table
	private Hashtable filterTable = new Hashtable();

	// development mode class path additions
	public static String devClassPath = null;
	// native library loading
	private static String libPrefix;
	private static String libSuffix;
	private static final String WIN_LIBRARY_PREFIX = "";
	private static final String WIN_LIBRARY_SUFFIX = ".dll";
	private static final String UNIX_LIBRARY_PREFIX = "lib";
	private static final String UNIX_LIBRARY_SUFFIX = ".so";
	private Hashtable nativeLibs = new Hashtable();
	private static final int BUF_SIZE = 32768;

	// control class load tracing
	public static boolean DEBUG = false;
	public static boolean DEBUG_SHOW_CREATE = true;
	public static boolean DEBUG_SHOW_ACTIVATE = true;
	public static boolean DEBUG_SHOW_ACTIONS = true;
	public static boolean DEBUG_SHOW_SUCCESS = true;
	public static boolean DEBUG_SHOW_FAILURE = true;
	public static String[] DEBUG_FILTER_CLASS = new String[0];
	public static String[] DEBUG_FILTER_LOADER = new String[0];
	public static String[] DEBUG_FILTER_RESOURCE = new String[0];
	public static String[] DEBUG_FILTER_NATIVE = new String[0];

	// DelegateLoader. Represents a single class loader this loader delegates to.
	protected static class DelegateLoader {

	private DelegatingURLClassLoader loader;
	private boolean isExported;

	public DelegateLoader(DelegatingURLClassLoader loader, boolean isExported) {
	this.loader = loader;
	this.isExported = isExported;
	}

	public Class loadClass(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
	if (isExported \|\| current == requestor)
	return loader.loadClass(name, false, requestor, seen, false);
	else
	return null;
	}

	public URL findResource(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
	if (isExported \|\| current == requestor)
	return loader.findResource(name, requestor, seen);
	else
	return null;
	}
	public Enumeration findResources(String name, DelegatingURLClassLoader current, DelegatingURLClassLoader requestor, Vector seen) {
	if (isExported \|\| current == requestor)
	return loader.findResources(name, requestor, seen);
	else
	return null;
	}
	}

	// unchecked DelegatingLoaderException
	protected static class DelegatingLoaderException extends RuntimeException {
	Exception e = null;

	public DelegatingLoaderException() {
	super();
	}

	public DelegatingLoaderException(String message) {
	super(message);
	}

	public DelegatingLoaderException(String message, Exception e) {
	super(message);
	this.e = e;
	}

	public Throwable getException() {
	return e;
	}
	}

	public DelegatingURLClassLoader(URL[] codePath, URLContentFilter[] codeFilters, URL[] resourcePath, URLContentFilter[] resourceFilters, ClassLoader parent) {
	super(codePath, parent);
	initialize();
	if (resourcePath != null)
	resourceLoader = new ResourceLoader(resourcePath);

	if (codePath != null) {
	if (codeFilters == null \|\| codeFilters.length != codePath.length)
	throw new DelegatingLoaderException();
	for (int i = 0; i < codePath.length; i++) {
	if (codeFilters[i] != null)
	filterTable.put(codePath[i], codeFilters[i]);
	}
	}
	if (resourcePath != null) {
	if (resourceFilters == null \|\| resourceFilters.length != resourcePath.length)
	throw new DelegatingLoaderException();
	for (int i = 0; i < resourcePath.length; i++) {
	if (resourceFilters[i] != null)
	filterTable.put(resourcePath[i], resourceFilters[i]);
	}
	}
	}
	/**
	* Returns the given class or <code>null</code> if the class is not visible to the
	* given requestor. The <code>inCache</code> flag controls how this action is
	* reported if in debug mode.
	*/
	protected Class checkClassVisibility(Class result, DelegatingURLClassLoader requestor, boolean inCache) {
	if (result == null)
	return null;
	if (isClassVisible(result, requestor)) {
	if (DEBUG && DEBUG_SHOW_SUCCESS && debugClass(result.getName()))
	debug("found " + result.getName() + " in " + (inCache ? "cache" : getURLforClass(result).toExternalForm()));
	} else {
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(result.getName()))
	debug("skip " + result.getName() + " in " + (inCache ? "cache" : getURLforClass(result).toExternalForm()));
	return null;
	}
	return result;
	}
	/**
	* Returns the given resource URL or <code>null</code> if the resource is not visible to the
	* given requestor.
	*/
	protected URL checkResourceVisibility(String name, URL result, DelegatingURLClassLoader requestor) {
	if (result == null)
	return null;
	if (isResourceVisible(name, result, requestor)) {
	if (DEBUG && DEBUG_SHOW_SUCCESS && debugResource(name))
	debug("found " + result);
	} else {
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
	debug("skip " + result);
	result = null;
	}
	return result;
	}
	protected void debug(String s) {

	System.out.println(toString()+"^"+Integer.toHexString(Thread.currentThread().hashCode())+" "+s);
	}
	protected boolean debugClass(String name) {

	if (debugLoader()) {
	return debugMatchesFilter(name,DEBUG_FILTER_CLASS);
	}
	return false;
	}
	protected void debugConstruction() {
	if (DEBUG && DEBUG_SHOW_CREATE && debugLoader()) {
	URL[] urls = getURLs();
	debug("Class Loader Created");
	debug("> baseURL=" + base);
	if (urls == null \|\| urls.length == 0)
	debug("> empty search path");
	else {
	URLContentFilter filter;
	for (int i = 0; i < urls.length; i++) {
	debug("> searchURL=" + urls[i].toString());
	filter = (URLContentFilter) filterTable.get(urls[i]);
	if (filter != null)
	debug("> export=" + filter.toString());
	}
	}
	}
	}
	protected String debugId() {
	return "";
	}
	protected boolean debugLoader() {

	return debugMatchesFilter(debugId(),DEBUG_FILTER_LOADER);
	}
	private boolean debugMatchesFilter(String name, String[] filter) {

	if (filter.length==0) return false;

	for (int i=0; i<filter.length; i++) {
	if (filter[i].equals("*")) return true;
	if (name.startsWith(filter[i])) return true;
	}
	return false;
	}
	protected boolean debugNative(String name) {

	if (debugLoader()) {
	return debugMatchesFilter(name,DEBUG_FILTER_NATIVE);
	}
	return false;
	}
	protected boolean debugResource(String name) {

	if (debugLoader()) {
	return debugMatchesFilter(name,DEBUG_FILTER_RESOURCE);
	}
	return false;
	}
	/**
	* Looks for the requested class in the parent of this loader using
	* standard Java protocols. If the parent is null then the system class
	* loader is consulted. <code>null</code> is returned if the class could
	* not be found.
	*/
	protected Class findClassParents(String name, boolean resolve) {
	try {
	ClassLoader parent = getParent();
	if (parent == null)
	return findSystemClass(name);
	return parent.loadClass(name);
	} catch (ClassNotFoundException e) {
	}
	return null;
	}
	/**
	* Finds and loads the class with the specified name from the URL search
	* path. Any URLs referring to JAR files are loaded and opened as needed
	* until the class is found. Search on the parent chain and then self.
	*
	* Subclasses should implement this method.
	*
	* @param name the name of the class
	* @param resolve whether or not to resolve the class if found
	* @param requestor class loader originating the request
	* @param checkParents whether the parent of this loader should be consulted
	* @return the resulting class
	*/
	protected abstract Class findClassParentsSelf(final String name, boolean resolve, DelegatingURLClassLoader requestor, boolean checkParents);
	/**
	* Finds and loads the class with the specified name from the URL search
	* path. Any URLs referring to JAR files are loaded and opened as needed
	* until the class is found. This method consults only the platform class loader.
	*
	* @param name the name of the class
	* @param resolve whether or not to resolve the class if found
	* @param requestor class loader originating the request
	* @param checkParents whether the parent of this loader should be consulted
	* @return the resulting class
	*/
	protected Class findClassPlatform(String name, boolean resolve, DelegatingURLClassLoader requestor, boolean checkParents) {
	DelegatingURLClassLoader platform = PlatformClassLoader.getDefault();
	if (this == platform)
	return null;
	return platform.findClassParentsSelf(name, resolve, requestor, false);
	}
	/**
	* Finds and loads the class with the specified name from the URL search
	* path. Any URLs referring to JAR files are loaded and opened as needed
	* until the class is found. This method considers only the classes loadable
	* by its explicit prerequisite loaders.
	*
	* @param name the name of the class
	* @param requestor class loader originating the request
	* @param seen list of delegated class loaders already searched
	* @return the resulting class
	*/
	protected Class findClassPrerequisites(final String name, DelegatingURLClassLoader requestor, Vector seen) {
	if (imports == null)
	return null;
	if (seen == null)
	seen = new Vector(); // guard against delegation loops
	seen.addElement(this);
	// Grab onto the imports value to protect against concurrent write.
	DelegateLoader[] loaders = imports;
	for (int i = 0; i < loaders.length; i++) {
	Class result = loaders[i].loadClass(name, this, requestor, seen);
	if (result != null)
	return result;
	}
	return null;
	}
	/**
	* Finds the resource with the specified name on the URL search path.
	* This method is used specifically to find the file containing a class to verify
	* that the class exists without having to load it.
	* Returns a URL for the resource. Searches only this loader's classpath.
	* <code>null</code> is returned if the resource cannot be found.
	*
	* @param name the name of the resource
	*/
	protected URL findClassResource(String name) {
	return super.findResource(name);
	}
	/**
	* Returns the absolute path name of a native library. The VM
	* invokes this method to locate the native libraries that belong
	* to classes loaded with this class loader. If this method returns
	* <code>null</code>, the VM searches the library along the path
	* specified as the <code>java.library.path</code> property.
	*
	* @param libname the library name
	* @return the absolute path of the native library
	*/
	protected String findLibrary(String libname) {
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugNative(libname))
	debug("findLibrary(" + libname + ")");

	if (base == null)
	return null;
	File libFile = null;
	String osLibFileName = libPrefix + libname + libSuffix;
	if (base.getProtocol().equals(PlatformURLHandler.FILE) \|\| base.getProtocol().equals(PlatformURLHandler.VA)) {
	// directly access library
	String libFileName = (base.getFile() + osLibFileName).replace('/', File.separatorChar);
	libFile = new File(libFileName);
	} else
	if (base.getProtocol().equals(PlatformURLHandler.PROTOCOL))
	// access library through eclipse URL
	libFile = getNativeLibraryAsLocal(osLibFileName);

	if (libFile == null)
	return null;
	if (!libFile.exists()) {
	if (DEBUG && DEBUG_SHOW_FAILURE && debugNative(libname))
	debug("not found " + libname);
	return null; // can't find the file
	}

	if (DEBUG && DEBUG_SHOW_SUCCESS && debugNative(libname))
	debug("found " + libname + " as " + libFile.getAbsolutePath());

	return libFile.getAbsolutePath();
	}
	/**
	* Finds the resource with the specified name on the URL search path.
	* Returns a URL for the resource. If resource is not found in own
	* URL search path, delegates search to prerequisite loaders.
	* Null is returned if none of the loaders find the resource.
	*
	* @param name the name of the resource
	*/
	public URL findResource(String name) {
	return findResource(name, this, null);
	}
	/**
	* Delegated resource access call.
	* Does not check prerequisite loader parent chain.
	*/
	protected URL findResource(String name, DelegatingURLClassLoader requestor, Vector seen) {
	// guard against delegation loops
	if (seen != null && seen.contains(this))
	return null;

	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
	debug("findResource(" + name + ")");

	// check the normal class path for self
	URL result = super.findResource(name);
	result = checkResourceVisibility(name, result, requestor);
	if (result != null)
	return result;

	// check our extra resource path if any
	if (resourceLoader != null) {
	result = resourceLoader.findResource(name);
	result = checkResourceVisibility(name, result, requestor);
	if (result != null)
	return result;
	}

	// delegate down the prerequisite chain if we haven't found anything yet.
	if (imports != null) {
	if (seen == null)
	seen = new Vector(); // guard against delegation loops
	seen.addElement(this);
	for (int i = 0; i < imports.length && result == null; i++)
	result = imports[i].findResource(name, this, requestor, seen);
	}
	return result;
	}
	/**
	* Returns an Enumeration of URLs representing all of the resources
	* on the URL search path having the specified name.
	*
	* @param name the resource name
	*/
	public Enumeration findResources(String name) throws IOException {
	return findResources(name, this, null);
	}
	/**
	* Delegated call to locate all named resources.
	* Does not check prerequisite loader parent chain.
	*/
	private Enumeration findResources(String name, DelegatingURLClassLoader requestor, Vector seen) {
	// guard against delegation loops
	if (seen != null && seen.contains(this))
	return null;

	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
	debug("findResources(" + name + ")");

	// check own URL search path
	Enumeration e = null;
	try {
	e = super.findResources(name);
	} catch (IOException ioe) {
	}
	ResourceEnumeration result = new ResourceEnumeration(name, e, this, requestor);

	// delegate down the prerequisite chain
	if (imports != null) {
	if (seen == null)
	seen = new Vector(); // guard against delegation loops
	seen.addElement(this);
	for (int i = 0; i < imports.length; i++)
	result.add(imports[i].findResources(name, this, requestor, seen));
	}

	return result;
	}
	private File getNativeLibraryAsLocal(String osname) {
	File result = null;
	try {
	URL liburl = new URL(base, osname);
	PlatformURLConnection c = (PlatformURLConnection) liburl.openConnection();
	URL localName = c.getURLAsLocal();
	result = new File(localName.getFile());
	} catch (IOException e) {
	}
	return result;
	}
	public URL getResource(String name) {
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugResource(name))
	debug("getResource(" + name + ")");

	URL result = super.getResource(name);
	if (result == null) {
	if (DEBUG && DEBUG_SHOW_FAILURE && debugResource(name))
	debug("not found " + name);
	}
	return result;
	}
	private URL getURLforClass(Class clazz) {
	ProtectionDomain pd = clazz.getProtectionDomain();
	if (pd != null) {
	CodeSource cs = pd.getCodeSource();
	if (cs != null)
	return cs.getLocation();
	}
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(clazz.getName()))
	debug("*** " + clazz.getName());
	return null;
	}
	private void initialize() {
	if (BootLoader.getOS().equals(BootLoader.OS_WIN32)) {
	libPrefix = WIN_LIBRARY_PREFIX;
	libSuffix = WIN_LIBRARY_SUFFIX;
	} else {
	libPrefix = UNIX_LIBRARY_PREFIX;
	libSuffix = UNIX_LIBRARY_SUFFIX;
	}
	}
	public void initializeImportedLoaders() {
	}
	/**
	* check to see if class is visible (exported)
	*/
	boolean isClassVisible(Class clazz, DelegatingURLClassLoader requestor) {
	URL lib = getURLforClass(clazz);
	if (lib == null)
	return true; // have a system class (see comment below)

	URLContentFilter filter = (URLContentFilter) filterTable.get(lib);
	if (filter == null) {
	// This code path is being executed because some VMs (eg. Sun JVM)
	// return from the class cache classes that were not loaded
	// by this class loader. Consequently we do not find the
	// corresponding jar filter. This appears to be a performance
	// optimization that we are defeating with our filtering scheme.
	// We return the class if it is a system class (see above). Otherwise
	// we reject the class which caused the load to be
	// delegated down the prerequisite chain until we find the
	// correct loader.
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(clazz.getName()))
	debug("*** Unable to find library filter for " + clazz.getName() + " from " + lib);
	return false;
	} else
	return filter.isClassVisible(clazz, this, requestor);
	}
	/**
	* check to see if resource is visible (exported)
	*/
	boolean isResourceVisible(String name, URL resource, DelegatingURLClassLoader requestor) {
	URL lib = null;
	String file = resource.getFile();
	try {
	lib = new URL(resource.getProtocol(), resource.getHost(), file.substring(0, file.length() - name.length()));
	} catch (MalformedURLException e) {
	if (DEBUG)
	debug("Unable to determine resource lib for " + name + " from " + resource);
	return false;
	}

	URLContentFilter filter = (URLContentFilter) filterTable.get(lib);
	if (filter == null) {
	if (DEBUG)
	debug("Unable to find library filter for " + name + " from " + lib);
	return false;
	} else
	return filter.isResourceVisible(name, this, requestor);
	}
	/**
	* Non-delegated load call. This method is not synchronized. Implementations of
	* findClassParentsSelf, and perhaps others, should synchronize themselves as
	* required. Synchronizing this method is too coarse-grained. It results in plugin
	* activation being synchronized and may cause deadlock.
	*/
	protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
	if (DEBUG && DEBUG_SHOW_ACTIONS && debugClass(name))
	debug("loadClass(" + name + ")");
	Class result = loadClass(name, resolve, this, null, true);
	if (result == null) {
	if (DEBUG && DEBUG_SHOW_FAILURE && debugClass(name))
	debug("not found " + name);
	throw new ClassNotFoundException(name);
	}
	return result;
	}
	/**
	* Delegated load call. This method is not synchronized. Implementations of
	* findClassParentsSelf, and perhaps others, should synchronize themselves as
	* required. Synchronizing this method is too coarse-grained. It results in plugin
	* activation being synchronized and may cause deadlock.
	*/
	private Class loadClass(String name, boolean resolve, DelegatingURLClassLoader requestor, Vector seen, boolean checkParents) {
	// guard against delegation loops
	if (seen != null && seen.contains(this))
	return null;

	// look in the parents and self
	Class result = findClassParentsSelf(name, resolve, requestor, checkParents);

	// search platform
	if (result == null)
	result = findClassPlatform(name, resolve, requestor, false);

	// search prerequisites
	if (result == null)
	result = findClassPrerequisites(name, requestor, seen);

	// if we found a class, consider resolving it
	if (result != null && resolve)
	resolveClass(result);

	return result;
	}
	protected void setImportedLoaders(DelegateLoader[] loaders) {

	imports = loaders;

	if(DEBUG && DEBUG_SHOW_CREATE && debugLoader()) {
	debug("Imports");
	if (imports==null \|\| imports.length==0) debug("> none");
	else {
	for (int i=0; i<imports.length; i++) {
	debug("> " + imports[i].loader.toString() + " export=" + imports[i].isExported);
	}
	}
	}
	}
	public String toString() {
	return "Loader [" + debugId() + "]";
	}
	}