core/src/main/java/org/apache/commons/proxy2/impl/AbstractProxyClassGenerator.java

/*
 * 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.proxy2.impl;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * A useful superclass for {@link ProxyClassGenerator} implementations.
 * 
 * @author James Carman
 * @since 1.0
 */
public abstract class AbstractProxyClassGenerator implements ProxyClassGenerator
{
    //******************************************************************************************************************
    // Static Methods
    //******************************************************************************************************************

    /**
     * Returns all methods that a proxy class must implement from the proxy interfaces. This method makes sure there are
     * no method signature clashes. For methods with the same signature (name and parameter types), the one encountered
     * first will be returned in the result. Final methods are also excluded from the result.
     * 
     * @param proxyClasses
     *            the interfaces the proxy class must implement
     * @return all methods that the proxy class must implement
     */
    public static Method[] getImplementationMethods(Class<?>[] proxyClasses)
    {
        final Map<MethodSignature, Method> signatureMethodMap = new HashMap<MethodSignature, Method>();
        final Set<MethodSignature> finalizedSignatures = new HashSet<MethodSignature>();
        for (int i = 0; i < proxyClasses.length; i++)
        {
            Class<?> proxyInterface = proxyClasses[i];
            final Method[] methods = proxyInterface.getMethods();
            for (int j = 0; j < methods.length; j++)
            {
                final MethodSignature signature = new MethodSignature(methods[j]);
                if (Modifier.isFinal(methods[j].getModifiers()))
                {
                    finalizedSignatures.add(signature);
                }
                else if (!signatureMethodMap.containsKey(signature))
                {
                    signatureMethodMap.put(signature, methods[j]);
                }
            }
        }
        final Collection<Method> resultingMethods = signatureMethodMap.values();
        for (MethodSignature signature : finalizedSignatures)
        {
            resultingMethods.remove(signatureMethodMap.get(signature));
        }
        return resultingMethods.toArray(new Method[resultingMethods.size()]);
    }
}