classloader.java

gcc3.2.1源代码

   *       compile-time constant initializer.
   * <LI>  Create the internal representation of the ``vtable''.
   * </UL>
   * For <code>gcj</code>-compiled classes, only the first step is
   * performed.  The compiler will have done the rest already.
   * <P>
   * This is called by the system automatically,
   * as part of class initialization; there is no reason to ever call
   * this method directly.  
   * <P> 
   * For historical reasons, this method has a name which is easily
   * misunderstood.  Java classes are never ``resolved''.  Classes are
   * linked; whereas method and field references are resolved.
   *
   * @param     clazz the class to link.
   * @exception java.lang.LinkageError
   */
  protected final void resolveClass(Class clazz)
  {
    resolveClass0(clazz);
  }

  static void resolveClass0(Class clazz)
  {
    synchronized (clazz)
      {
	try {
	  linkClass0 (clazz);
	} catch (Throwable x) {
	  markClassErrorState0 (clazz);

	  if (x instanceof Error)
	    throw (Error)x;
	  else    
	    throw new java.lang.InternalError
	      ("unexpected exception during linking: " + x);
	}
      }
  }

  /** Internal method.  Calls _Jv_PrepareClass and
   * _Jv_PrepareCompiledClass.  This is only called from resolveClass.  */ 
  private static native void linkClass0(Class clazz);

  /** Internal method.  Marks the given clazz to be in an erroneous
   * state, and calls notifyAll() on the class object.  This should only
   * be called when the caller has the lock on the class object.  */
  private static native void markClassErrorState0(Class clazz);

  /**
   * Defines a new package and creates a Package object.
   * The package should be defined before any class in the package is
   * defined with <code>defineClass()</code>. The package should not yet
   * be defined before in this classloader or in one of its parents (which
   * means that <code>getPackage()</code> should return <code>null</code>).
   * All parameters except the <code>name</code> of the package may be
   * <code>null</code>.
   * <p>
   * Subclasses should call this method from their <code>findClass()</code>
   * implementation before calling <code>defineClass()</code> on a Class
   * in a not yet defined Package (which can be checked by calling
   * <code>getPackage()</code>).
   *
   * @param name The name of the Package
   * @param specTitle The name of the specification
   * @param specVendor The name of the specification designer
   * @param specVersion The version of this specification
   * @param implTitle The name of the implementation
   * @param implVendor The vendor that wrote this implementation
   * @param implVersion The version of this implementation
   * @param sealed If sealed the origin of the package classes
   * @return the Package object for the specified package
   *
   * @exception IllegalArgumentException if the package name is null or if
   * it was already defined by this classloader or one of its parents.
   *
   * @see Package
   * @since 1.2
   */
  protected Package definePackage(String name,
				  String specTitle, String specVendor,
				  String specVersion, String implTitle,
				  String implVendor, String implVersion,
				  URL sealed)
  {
    if (getPackage(name) != null)
      throw new IllegalArgumentException("Package " + name
					 + " already defined");
    Package p = new Package(name,
			    specTitle, specVendor, specVersion,
			    implTitle, implVendor, implVersion,
			    sealed);
    synchronized (definedPackages)
    {
      definedPackages.put(name, p);
    }
    return p;
  }

  /**
   * Returns the Package object for the requested package name. It returns
   * null when the package is not defined by this classloader or one of its
   * parents.
   *
   * @since 1.2
   */
  protected Package getPackage(String name)
  {
    Package p;
    if (parent == null)
      // XXX - Should we use the bootstrap classloader?
      p = null;
    else
      p = parent.getPackage(name);

    if (p == null)
      {
        synchronized (definedPackages)
	{
	  p = (Package) definedPackages.get(name);
	}
      }

    return p;
  }

  /**
   * Returns all Package objects defined by this classloader and its parents.
   *
   * @since 1.2
   */
  protected Package[] getPackages()
  {
    Package[] allPackages;

    // Get all our packages.
    Package[] packages;
    synchronized(definedPackages)
    {
      packages = new Package[definedPackages.size()];
      definedPackages.values().toArray(packages);
    }

    // If we have a parent get all packages defined by our parents.
    if (parent != null)
      {
	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;
  }

  /** 
   * 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);
  }

  /*
   * Does currently nothing. FIXME.
   */ 
  protected final void setSigners(Class claz, Object[] signers) {
    /* claz.setSigners (signers); */
  }

  /**
   * 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>.  (Unlike the JDK this is native,
   * since we implement the class table internally.)
   * @param     name  class to find.
   * @return    the class loaded, or null.
   */ 
  protected final native Class findLoadedClass(String name);

  public static InputStream getSystemResourceAsStream(String name) {
    return getSystemClassLoader().getResourceAsStream (name);
  }

  public static URL getSystemResource(String name) {
    return getSystemClassLoader().getResource (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);
  }

  protected URL findResource (String name)
  {
    // Default to returning null.  Derived classes implement this.
    return null;
  }

  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);
  }

  protected Enumeration findResources (String name) throws IOException
  {
    // Default to returning null.  Derived classes implement this.
    return null;
  }
}