ProxyFactory.java

/**
 * Copyright 2001-2010 the original author or authors.
 *
 * Licensed 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 be.selckin.swu.pmodel;

import net.sf.cglib.core.CollectionUtils;
import net.sf.cglib.core.VisibilityPredicate;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import org.objenesis.Objenesis;
import org.objenesis.ObjenesisStd;

import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.List;

/**
 * Some code based on and taken from EasyMock
 */
public class ProxyFactory {

    private final Objenesis objenesis = new ObjenesisStd();

    @SuppressWarnings("unchecked")
    public <T> T createProxy(Class<T> type, InvocationHandler handler) {
        MethodInterceptor interceptor = new ProxyMethodInterceptor(handler);

        Enhancer enhancer = new Enhancer() {
            @SuppressWarnings("unchecked")
            @Override
            protected void filterConstructors(Class sc, List constructors) {
                CollectionUtils.filter(constructors, new VisibilityPredicate(sc, true));
            }
        };
        enhancer.setUseCache(false);
        enhancer.setSuperclass(type);
        enhancer.setCallbackType(interceptor.getClass());

        Class<?> mockClass = enhancer.createClass();

        Enhancer.registerCallbacks(mockClass, null);
        Enhancer.registerStaticCallbacks(mockClass, new Callback[]{interceptor});
        Factory mock = (Factory) objenesis.newInstance(mockClass);

        // cglib has code that normally gets called in the constructor, but we instantiated the class without calling the constructor,
        // so call the cglib code this way.
        mock.getCallback(0);
        return (T) mock;
    }

    public static class ProxyMethodInterceptor implements MethodInterceptor, Serializable {

        private final InvocationHandler handler;

        public ProxyMethodInterceptor(InvocationHandler handler) {
            this.handler = handler;
        }

        @SuppressWarnings("ProhibitedExceptionDeclared")
        @Override
        public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
            return handler.invoke(obj, method, args);
        }
    }
}