proxy.java

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   * @return the generated proxy class
   * @throws IllegalArgumentException if the constraints for getProxyClass
   *         were violated, except for problems with null
   * @throws NullPointerException if `interfaces' is null or contains
   *         a null entry, or if handler is null
   * @see Configuration#HAVE_NATIVE_GET_PROXY_CLASS
   * @see #getProxyClass(ClassLoader, Class[])
   * @see #getProxyData0(ClassLoader, Class[])
   * @see #generateProxyClass0(ProxyData)
   */
  private static native Class getProxyClass0(ClassLoader loader,
                                             Class[] interfaces);

  /**
   * Optional native method to replace (and speed up) the pure Java
   * implementation of getProxyData.  Only needed if
   * Configuration.HAVE_NATIVE_GET_PROXY_DATA is true. The native code
   * may safely assume that a new ProxyData object must be created which
   * does not duplicate any existing ones.
   *
   * @param loader the class loader to define the proxy class in; null
   *        implies the bootstrap class loader
   * @param interfaces the interfaces the class will extend
   * @return all data that is required to make this proxy class
   * @throws IllegalArgumentException if the constraints for getProxyClass
   *         were violated, except for problems with null
   * @throws NullPointerException if `interfaces' is null or contains
   *         a null entry, or if handler is null
   * @see Configuration.HAVE_NATIVE_GET_PROXY_DATA
   * @see #getProxyClass(ClassLoader, Class[])
   * @see #getProxyClass0(ClassLoader, Class[])
   * @see ProxyType#getProxyData()
   */
  private static native ProxyData getProxyData0(ClassLoader loader,
                                                Class[] interfaces);

  /**
   * Optional native method to replace (and speed up) the pure Java
   * implementation of generateProxyClass.  Only needed if
   * Configuration.HAVE_NATIVE_GENERATE_PROXY_CLASS is true. The native
   * code may safely assume that a new Class must be created, and that
   * the ProxyData object does not describe any existing class.
   *
   * @param loader the class loader to define the proxy class in; null
   *        implies the bootstrap class loader
   * @param data the struct of information to convert to a Class. This
   *        has already been verified for all problems except exceeding
   *        VM limitations
   * @return the newly generated class
   * @throws IllegalArgumentException if VM limitations are exceeded
   * @see #getProxyClass(ClassLoader, Class[])
   * @see #getProxyClass0(ClassLoader, Class[])
   * @see ProxyData#generateProxyClass(ClassLoader)
   */
  private static native Class generateProxyClass0(ClassLoader loader,
                                                  ProxyData data);

  /**
   * Helper class for mapping unique ClassLoader and interface combinations
   * to proxy classes.
   *
   * @author Eric Blake <[e-mail]>
   */
  private static final class ProxyType
  {
    /**
     * Store the class loader (may be null)
     */
    final ClassLoader loader;

    /**
     * Store the interfaces (never null, all elements are interfaces)
     */
    final Class[] interfaces;

    /**
     * Construct the helper object.
     *
     * @param loader the class loader to define the proxy class in; null
     *        implies the bootstrap class loader
     * @param interfaces an array of interfaces
     */
    ProxyType(ClassLoader loader, Class[] interfaces)
    {
      if (loader == null)
         loader = ClassLoader.getSystemClassLoader();
      this.loader = loader;
      this.interfaces = interfaces;
    }

    /**
     * Calculates the hash code.
     *
     * @return a combination of the classloader and interfaces hashcodes.
     */
    public int hashCode()
    {
      //loader is always not null
      int hash = loader.hashCode();
      for (int i = 0; i < interfaces.length; i++)
        hash = hash * 31 + interfaces[i].hashCode();
      return hash;
    }

    // A more comprehensive comparison of two arrays,
    //   ignore array element order, and
    //   ignore redundant elements
    private static boolean sameTypes(Class arr1[], Class arr2[]) {
      if (arr1.length == 1 && arr2.length == 1) {
        return arr1[0] == arr2[0];
      }
        
      // total occurrance of elements of arr1 in arr2
      int total_occ_of_arr1_in_arr2 = 0;
    each_type:
      for (int i = arr1.length; --i >= 0; ) 
      {
        Class t = arr1[i];
        for (int j = i; --j >= 0; ) 
        {
          if (t == arr1[j]) 
          { //found duplicate type
            continue each_type;  
          }
        }
            
        // count c(a unique element of arr1)'s 
        //   occurrences in arr2
        int occ_in_arr2 = 0;
        for (int j = arr2.length; --j >= 0; ) 
        {
          if (t == arr2[j]) 
          {
            ++occ_in_arr2;
          }
        }
        if (occ_in_arr2 == 0) 
        { // t does not occur in arr2
          return false;
        }
        
        total_occ_of_arr1_in_arr2 += occ_in_arr2;
      }
      // now, each element of arr2 must have been visited
      return total_occ_of_arr1_in_arr2 == arr2.length;
    }

    /**
     * Calculates equality.
     *
     * @param the object to compare to
     * @return true if it is a ProxyType with same data
     */
    public boolean equals(Object other)
    {
      ProxyType pt = (ProxyType) other;
      if (loader != pt.loader || interfaces.length != pt.interfaces.length)
        return false;
	  return sameTypes(interfaces, pt.interfaces);
    }
  } // class ProxyType

  /**
   * Helper class which allows hashing of a method name and signature
   * without worrying about return type, declaring class, or throws clause,
   * and which reduces the maximally common throws clause between two methods
   *
   * @author Eric Blake <[e-mail]>
   */
  private static final class ProxySignature
  {
    /**
     * The core signatures which all Proxy instances handle.
     */
    static final HashMap coreMethods = new HashMap();
    static
    {
      try
        {
          ProxySignature sig
            = new ProxySignature(Object.class
                                 .getMethod("equals",
                                            new Class[] {Object.class}));
          coreMethods.put(sig, sig);
          sig = new ProxySignature(Object.class.getMethod("hashCode", null));
          coreMethods.put(sig, sig);
          sig = new ProxySignature(Object.class.getMethod("toString", null));
          coreMethods.put(sig, sig);
        }
      catch (Exception e)
        {
          // assert false;
          throw (Error) new InternalError("Unexpected: " + e).initCause(e);
        }
    }

    /**
     * The underlying Method object, never null
     */
    final Method method;

    /**
     * The set of compatible thrown exceptions, may be empty
     */
    final Set exceptions = new HashSet();

    /**
     * Construct a signature
     *
     * @param method the Method this signature is based on, never null
     */
    ProxySignature(Method method)
    {
      this.method = method;
      Class[] exc = method.getExceptionTypes();
      int i = exc.length;
      while (--i >= 0)
        {
          // discard unchecked exceptions
          if (Error.class.isAssignableFrom(exc[i])
              || RuntimeException.class.isAssignableFrom(exc[i]))
            continue;
          exceptions.add(exc[i]);
        }
    }

    /**
     * Given a method, make sure it's return type is identical
     * to this, and adjust this signature's throws clause appropriately
     *
     * @param other the signature to merge in
     * @throws IllegalArgumentException if the return types conflict
     */
    void checkCompatibility(ProxySignature other)
    {
      if (method.getReturnType() != other.method.getReturnType())
        throw new IllegalArgumentException("incompatible return types: "
                                           + method + ", " + other.method);

      // if you can think of a more efficient way than this O(n^2) search,
      // implement it!
      int size1 = exceptions.size();
      int size2 = other.exceptions.size();
      boolean[] valid1 = new boolean[size1];
      boolean[] valid2 = new boolean[size2];
      Iterator itr = exceptions.iterator();
      int pos = size1;
      while (--pos >= 0)
        {
          Class c1 = (Class) itr.next();
          Iterator itr2 = other.exceptions.iterator();
          int pos2 = size2;
          while (--pos2 >= 0)
            {
              Class c2 = (Class) itr2.next();
              if (c2.isAssignableFrom(c1))
                valid1[pos] = true;
              if (c1.isAssignableFrom(c2))
                valid2[pos2] = true;
            }
        }
      pos = size1;
      itr = exceptions.iterator();
      while (--pos >= 0)
        {
          itr.next();
          if (! valid1[pos])
            itr.remove();
        }
      pos = size2;
      itr = other.exceptions.iterator();
      while (--pos >= 0)
        {
          itr.next();
          if (! valid2[pos])
            itr.remove();
        }
      exceptions.addAll(other.exceptions);
    }

    /**
     * Calculates the hash code.
     *
     * @return a combination of name and parameter types
     */
    public int hashCode()
    {
      int hash = method.getName().hashCode();
      Class[] types = method.getParameterTypes();
      for (int i = 0; i < types.length; i++)
        hash = hash * 31 + types[i].hashCode();
      return hash;
    }

    /**
     * Calculates equality.
     *
     * @param the object to compare to
     * @return true if it is a ProxySignature with same data
     */
    public boolean equals(Object other)
    {
      ProxySignature ps = (ProxySignature) other;
      Class[] types1 = method.getParameterTypes();
      Class[] types2 = ps.method.getParameterTypes();
      if (! method.getName().equals(ps.method.getName())
          || types1.length != types2.length)
        return false;
      int i = types1.length;
      while (--i >= 0)
        if (types1[i] != types2[i])
          return false;
      return true;
    }
  } // class ProxySignature

  /**
   * A flat representation of all data needed to generate bytecode/instantiate
   * a proxy class.  This is basically a struct.
   *
   * @author Eric Blake <[e-mail]>
   */
  private static final class ProxyData
  {
    /**
     * The package this class is in.  Possibly null, meaning the unnamed
     * package.
     */
    Package pack;

    /**
     * The interfaces this class implements.  Non-null, but possibly empty.
     */
    Class[] interfaces;

    /**
     * The Method objects this class must pass as the second argument to
     * invoke (also useful for determining what methods this class has).
     * Non-null, non-empty (includes at least Object.hashCode, Object.equals,
     * and Object.toString).
     */
    Method[] methods;

    /**
     * The exceptions that do not need to be wrapped in
     * UndeclaredThrowableException. exceptions[i] is the same as, or a
     * subset of subclasses, of methods[i].getExceptionTypes(), depending on
     * compatible throws clauses with multiple inheritance. It is unspecified
     * if these lists include or exclude subclasses of Error and
     * RuntimeException, but excluding them is harmless and generates a
     * smaller class.
     */
    Class[][] exceptions;

    /**
     * For unique id's
     */
    private static int count = 0;

    /**
     * The id of this proxy class
     */
    final int id = count++;

    /**
     * Construct a ProxyData with uninitialized data members.
     */
    ProxyData()
    {
    }

    /**
     * Verifies that the arguments are legal, and sets up remaining data
     * This should only be called when a class must be generated, as
     * it is expensive.
     *
     * @param pt the ProxyType to convert to ProxyData
     * @return the flattened, verified ProxyData structure for use in
     *         class generation
     * @throws IllegalArgumentException if `interfaces' contains
     *         non-interfaces or incompatible combinations, and verify is true
     * @throws NullPointerException if interfaces is null or contains null
     */
    static ProxyData getProxyData(ProxyType pt)
    {
      Map method_set = (Map) ProxySignature.coreMethods.clone();
      boolean in_package = false; // true if we encounter non-public interface

      ProxyData data = new ProxyData();
      data.interfaces = pt.interfaces;

      // if interfaces is too large, we croak later on when the constant
      // pool overflows
      int i = data.interfaces.length;
      while (--i >= 0)
        {
          Class inter = data.interfaces[i];
          if (! inter.isInterface())
            throw new IllegalArgumentException("not an interface: " + inter);
          try
            {
              if (Class.forName(inter.getName(), false, pt.loader) != inter)
                throw new IllegalArgumentException("not accessible in "
                                                   + "classloader: " + inter);
            }
          catch (ClassNotFoundException e)
            {