| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.proxy.factory.util; |
| |
| import org.apache.commons.proxy.ProxyFactory; |
| import org.apache.commons.proxy.exception.ProxyFactoryException; |
| |
| import java.io.Serializable; |
| import java.lang.reflect.Constructor; |
| import java.lang.reflect.Modifier; |
| import java.util.Collection; |
| import java.util.LinkedList; |
| import java.util.List; |
| |
| /** |
| * A useful superclass for a {@link ProxyFactory} which supports subclassing rather than merely implementing interfaces. |
| * |
| * @author James Carman |
| * @since 1.0 |
| */ |
| public abstract class AbstractSubclassingProxyFactory extends ProxyFactory |
| { |
| //********************************************************************************************************************** |
| // Static Methods |
| //********************************************************************************************************************** |
| |
| /** |
| * Returns either {@link Object} if all of the <code>proxyClasses</code> are interfaces or the single non-interface |
| * class from <code>proxyClasses</code>. |
| * |
| * @param proxyClasses the proxy classes |
| * @return either {@link Object} if all of the <code>proxyClasses</code> are interfaces or the single non-interface |
| * class from <code>proxyClasses</code> |
| * @throws ProxyFactoryException if multiple non-interface classes are contained in <code>proxyClasses</code> or any |
| * of the non-interface classes are final |
| */ |
| public static Class getSuperclass( Class[] proxyClasses ) |
| { |
| final Class[] superclasses = toNonInterfaces(proxyClasses); |
| switch( superclasses.length ) |
| { |
| case 0: |
| return Object.class; |
| case 1: |
| final Class superclass = superclasses[0]; |
| if( Modifier.isFinal(superclass.getModifiers()) ) |
| { |
| throw new ProxyFactoryException( |
| "Proxy class cannot extend " + superclass.getName() + " as it is final."); |
| } |
| if( !hasSuitableDefaultConstructor(superclass) ) |
| { |
| throw new ProxyFactoryException("Proxy class cannot extend " + superclass.getName() + |
| ", because it has no visible \"default\" constructor."); |
| } |
| return superclass; |
| default: |
| final StringBuffer errorMessage = new StringBuffer("Proxy class cannot extend "); |
| for( int i = 0; i < superclasses.length; i++ ) |
| { |
| Class c = superclasses[i]; |
| errorMessage.append(c.getName()); |
| if( i != superclasses.length - 1 ) |
| { |
| errorMessage.append(", "); |
| } |
| } |
| errorMessage.append("; multiple inheritance not allowed."); |
| throw new ProxyFactoryException(errorMessage.toString()); |
| } |
| } |
| |
| private static boolean hasSuitableDefaultConstructor( Class superclass ) |
| { |
| final Constructor[] declaredConstructors = superclass.getDeclaredConstructors(); |
| for( int i = 0; i < declaredConstructors.length; i++ ) |
| { |
| Constructor constructor = declaredConstructors[i]; |
| if( constructor.getParameterTypes().length == 0 && ( Modifier.isPublic(constructor.getModifiers()) || |
| Modifier.isProtected(constructor.getModifiers()) ) ) |
| { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Returns the <code>proxyClasses</code> transformed into an array of only the interface classes. |
| * <p/> |
| * <b>Note</b>: This class will append {@link Serializable} to the end of the list if it's |
| * not found! |
| * |
| * @param proxyClasses the proxy classes |
| * @return the <code>proxyClasses</code> transformed into an array of only the interface classes |
| */ |
| protected static Class[] toInterfaces( Class[] proxyClasses ) |
| { |
| final Collection interfaces = new LinkedList(); |
| boolean serializableFound = false; |
| for( int i = 0; i < proxyClasses.length; i++ ) |
| { |
| Class proxyInterface = proxyClasses[i]; |
| if( proxyInterface.isInterface() ) |
| { |
| interfaces.add(proxyInterface); |
| } |
| serializableFound |= ( Serializable.class.equals(proxyInterface) ); |
| } |
| if( !serializableFound ) |
| { |
| interfaces.add(Serializable.class); |
| } |
| return ( Class[] ) interfaces.toArray(new Class[interfaces.size()]); |
| } |
| |
| private static Class[] toNonInterfaces( Class[] proxyClasses ) |
| { |
| final List superclasses = new LinkedList(); |
| for( int i = 0; i < proxyClasses.length; i++ ) |
| { |
| Class proxyClass = proxyClasses[i]; |
| if( !proxyClass.isInterface() ) |
| { |
| superclasses.add(proxyClass); |
| } |
| } |
| return ( Class[] ) superclasses.toArray(new Class[superclasses.size()]); |
| } |
| |
| //********************************************************************************************************************** |
| // Other Methods |
| //********************************************************************************************************************** |
| |
| /** |
| * Returns true if a suitable superclass can be found, given the desired <code>proxyClasses</code>. |
| * |
| * @param proxyClasses the proxy classes |
| * @return true if a suitable superclass can be found, given the desired <code>proxyClasses</code> |
| */ |
| public boolean canProxy( Class... proxyClasses ) |
| { |
| try |
| { |
| getSuperclass(proxyClasses); |
| return true; |
| } |
| catch( ProxyFactoryException e ) |
| { |
| return false; |
| } |
| } |
| } |
| |