classloader.java

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      {
	Package[] parentPackages = parent.getPackages();
	allPackages = new Package[parentPackages.length + packages.length];
	System.arraycopy(parentPackages, 0, allPackages, 0,
			 parentPackages.length);
	System.arraycopy(packages, 0, allPackages, parentPackages.length,
			 packages.length);
      }
    else
      // XXX - Should we use the bootstrap classloader?
      allPackages = packages;

    return allPackages;
  }

  /**
   * Called by <code>Runtime.loadLibrary()</code> to get an absolute path
   * to a (system specific) library that was requested by a class loaded
   * by this classloader. The default implementation returns
   * <code>null</code>. It should be implemented by subclasses when they
   * have a way to find the absolute path to a library. If this method
   * returns null the library is searched for in the default locations
   * (the directories listed in the <code>java.library.path</code> system
   * property).
   *
   * @param name the (system specific) name of the requested library
   * @return the full pathname to the requested library, or null
   * @see Runtime#loadLibrary()
   * @since 1.2
   */
  protected String findLibrary(String name)
  {
    return null;
  }

  /** 
   * Returns a class found in a system-specific way, typically
   * via the <code>java.class.path</code> system property.  Loads the 
   * class if necessary.
   *
   * @param     name the class to resolve.
   * @return    the class loaded.
   * @exception java.lang.LinkageError 
   * @exception java.lang.ClassNotFoundException 
   */
  protected final Class findSystemClass(String name) 
    throws java.lang.ClassNotFoundException
  {
    return gnu.gcj.runtime.VMClassLoader.instance.loadClass (name);
  }

  /**
   * Helper to set the signers of a class. This should be called after
   * defining the class.
   *
   * @param c the Class to set signers of
   * @param signers the signers to set
   * @since 1.1
   */   
  protected final void setSigners(Class c, Object[] signers)
  {
    /*
     * Does currently nothing. FIXME.
     */ 
  }

  /**
   * If a class named <code>name</code> was previously loaded using
   * this <code>ClassLoader</code>, then it is returned.  Otherwise
   * it returns <code>null</code>.
   * @param     name  class to find.
   * @return    the class loaded, or null.
   */ 
  protected final synchronized Class findLoadedClass(String name)
  {
    return (Class) loadedClasses.get(name);
  }

  /**
   * Get a resource using the system classloader.
   *
   * @param name the name of the resource relative to the system classloader
   * @return an input stream for the resource, or null
   * @since 1.1
   */
  public static InputStream getSystemResourceAsStream(String name) {
    return getSystemClassLoader().getResourceAsStream (name);
  }

  /**
   * Get the URL to a resource using the system classloader.
   *
   * @param name the name of the resource relative to the system classloader
   * @return the URL to the resource
   * @since 1.1
   */
  public static URL getSystemResource(String name) {
    return getSystemClassLoader().getResource (name);
  }

  /**
   * Get an Enumeration of URLs to resources with a given name using the
   * the system classloader. The enumeration firsts lists the resources with
   * the given name that can be found by the bootstrap classloader followed
   * by the resources with the given name that can be found on the classpath.
   *
   * @param name the name of the resource relative to the system classloader
   * @return an Enumeration of URLs to the resources
   * @throws IOException if I/O errors occur in the process
   * @since 1.2
   */
  public static Enumeration getSystemResources(String name) throws IOException
  {
    return getSystemClassLoader().getResources(name);
  }

  /**
   *   Return an InputStream representing the resource name.  
   *   This is essentially like 
   *   <code>getResource(name).openStream()</code>, except
   *   it masks out any IOException and returns null on failure.
   * @param   name  resource to load
   * @return  an InputStream, or null
   * @see     java.lang.ClassLoader#getResource(String)
   * @see     java.io.InputStream
   */
  public InputStream getResourceAsStream(String name) 
  {
    try
      {
	URL res = getResource (name);
	if (res == null)
          return null;
	return res.openStream ();
      }
    catch (java.io.IOException x)
      {
	return null;
      }
  }
 
  /**
   * Return an java.io.URL representing the resouce <code>name</code>.  
   * The default implementation just returns <code>null</code>.
   * @param   name  resource to load
   * @return  a URL, or null if there is no such resource.
   * @see     java.lang.ClassLoader#getResourceAsBytes(String)
   * @see     java.lang.ClassLoader#getResourceAsStream(String)
   * @see     java.io.URL
   */
  public URL getResource (String name) 
  {
    // The rules say search the parent class if non-null,
    // otherwise search the built-in class loader (assumed to be
    // the system ClassLoader).  If not found, call
    // findResource().
    URL result = null;

    ClassLoader delegate = parent;

    if (delegate == null)
      delegate = getSystemClassLoader ();
	
    // Protect ourselves from looping.
    if (this != delegate)
      result = delegate.getResource (name);

    if (result != null)
      return result;
    else
      return findResource (name);
  }

  /**
   * Called whenever a resource is needed that could not be provided by
   * one of the parents of this classloader. It is called by
   * <code>getResource()</code> after <code>parent.getResource()</code>
   * couldn't provide the requested resource.
   *
   * <p>The default implementation always returns null. Subclasses should
   * override this method when they can provide a way to return a URL
   * to a named resource.
   *
   * @param name the name of the resource to be found
   * @return a URL to the named resource or null when not found
   * @since 1.2
   */
  protected URL findResource (String name)
  {
    // Default to returning null.  Derived classes implement this.
    return null;
  }

  /**
   * Returns an Enumeration of all resources with a given name that can
   * be found by this classloader and its parents. Certain classloaders
   * (such as the URLClassLoader when given multiple jar files) can have
   * multiple resources with the same name that come from multiple locations.
   * It can also occur that a parent classloader offers a resource with a
   * certain name and the child classloader also offers a resource with that
   * same name. <code>getResource() only offers the first resource (of the
   * parent) with a given name. This method lists all resources with the
   * same name. The name should use '/' as path separators.
   *
   * <p>The Enumeration is created by first calling <code>getResources()</code>
   * on the parent classloader and then calling <code>findResources()</code>
   * on this classloader.
   *
   * @param name the resource name
   * @return an enumaration of all resources found
   * @throws IOException if I/O errors occur in the process
   * @since 1.2
   */
  public final Enumeration getResources(String name) throws IOException
  {
    // The rules say search the parent class if non-null,
    // otherwise search the built-in class loader (assumed to be
    // the system ClassLoader).  If not found, call
    // findResource().
    Enumeration result = null;

    ClassLoader delegate = parent;

    if (delegate == null)
      delegate = getSystemClassLoader ();
	
    // Protect ourselves from looping.
    if (this != delegate)
      result = delegate.getResources (name);

    if (result != null)
      return result;
    else
      return findResources (name);
  }

  /**
   * Called whenever all locations of a named resource are needed.
   * It is called by <code>getResources()</code> after it has called
   * <code>parent.getResources()</code>. The results are combined by
   * the <code>getResources()</code> method.
   *
   * <p>The default implementation always returns an empty Enumeration.
   * Subclasses should override it when they can provide an Enumeration of
   * URLs (possibly just one element) to the named resource.
   * The first URL of the Enumeration should be the same as the one
   * returned by <code>findResource</code>.
   *
   * @param name the name of the resource to be found
   * @return a possibly empty Enumeration of URLs to the named resource
   * @throws IOException if I/O errors occur in the process
   * @since 1.2
   */
  protected Enumeration findResources(String name) throws IOException
  {
    return Collections.enumeration(Collections.EMPTY_LIST);
  }

  /**
   * Set the default assertion status for classes loaded by this classloader,
   * used unless overridden by a package or class request.
   *
   * @param enabled true to set the default to enabled
   * @see #setClassAssertionStatus(String, boolean)
   * @see #setPackageAssertionStatus(String, boolean)
   * @see #clearAssertionStatus()
   * @since 1.4
   */
  public void setDefaultAssertionStatus(boolean enabled)
  {
    defaultAssertionStatus = enabled;
  }

  /**
   * Set the default assertion status for packages, used unless overridden
   * by a class request. This default also covers subpackages, unless they
   * are also specified. The unnamed package should use null for the name.
   *
   * @param name the package (and subpackages) to affect
   * @param enabled true to set the default to enabled
   * @see #setDefaultAssertionStatus(String, boolean)
   * @see #setClassAssertionStatus(String, boolean)
   * @see #clearAssertionStatus()
   * @since 1.4
   */
  public synchronized void setPackageAssertionStatus(String name,
                                                     boolean enabled)
  {
    if (packageAssertionStatus == null)
      packageAssertionStatus
        = new HashMap(systemPackageAssertionStatus);
    packageAssertionStatus.put(name, Boolean.valueOf(enabled));
  }
  
  /**
   * Set the default assertion status for a class. This only affects the
   * status of top-level classes, any other string is harmless.
   *
   * @param name the class to affect
   * @param enabled true to set the default to enabled
   * @throws NullPointerException if name is null
   * @see #setDefaultAssertionStatus(String, boolean)
   * @see #setPackageAssertionStatus(String, boolean)
   * @see #clearAssertionStatus()
   * @since 1.4
   */
  public synchronized void setClassAssertionStatus(String name,
                                                   boolean enabled)
  {
    if (classAssertionStatus == null)
      classAssertionStatus = new HashMap(systemClassAssertionStatus);
    // The toString() hack catches null, as required.
    classAssertionStatus.put(name.toString(), Boolean.valueOf(enabled));
  }
  
  /**
   * Resets the default assertion status of this classloader, its packages
   * and classes, all to false. This allows overriding defaults inherited
   * from the command line.
   *
   * @see #setDefaultAssertionStatus(boolean)
   * @see #setClassAssertionStatus(String, boolean)
   * @see #setPackageAssertionStatus(String, boolean)
   * @since 1.4
   */
  public synchronized void clearAssertionStatus()
  {
    defaultAssertionStatus = false;
    packageAssertionStatus = new HashMap();
    classAssertionStatus = new HashMap();
  }
}