(原)Java動態代理實現（簡單AOP實現）

本文介紹了簡單Aop實現的方法，意在拋磚引玉。

首先是簡單的Aspect接口

package org.aspect;

/**
 * 切面接口
 */
public interface Aspect {

	/**
	 * 事先執行
	 */
	public void doBefore();

	/**
	 * 事後執行
	 */
	public void doAfter();
}

然後是代理工廠

package org.aspect;

import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

/**
 * 代理工廠類
 */
public class DynamicProxyFactory {

	/**
	 * 私有構造方法
	 */
	private DynamicProxyFactory() {}

	/**
	 * 工廠方法
	 * 
	 * @param instance 代理目標類實例對象
	 * @param aspect 切面對象
	 */
	public static Object newInstance(Object instance, Aspect aspect) {

		List<Aspect> aspectList = new ArrayList<Aspect>();
		aspectList.add(aspect);

		return newInstance(instance, aspectList);
	}

	/**
	 * 工廠方法
	 * 
	 * @param instance 代理目標類實例對象
	 * @param aspectList 切面集合
	 */
	public static Object newInstance(Object instance, List<Aspect> aspectList) {
		SimpleInvocationHandler hander = new SimpleInvocationHandler();
		hander.setAspectList(aspectList);
		hander.setSource(instance);
		return Proxy.newProxyInstance(instance.getClass().getClassLoader(), 
									  instance.getClass().getInterfaces(), 
									  hander);
	}
}

最後是代理執行類

package org.aspect;

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

/**
 * 代理委託接口實現
 */
public class SimpleInvocationHandler implements InvocationHandler {


	private Object source = null;

	private List<Aspect> aspectList = null;


	public Object getSource() {
		return source;
	}


	public void setSource(Object source) {
		this.source = source;
	}


	public List<Aspect> getAspectList() {
		return aspectList;
	}


	public void setAspectList(List<Aspect> aspectList) {
		this.aspectList = aspectList;
	}

	/**
	 * 委託方法
	 * 
	 * @param proxy 代理對象
	 * @param method 代理方法
	 * @param args 方法參數
	 */
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {

		for (Aspect aspect : aspectList) {
			aspect.doBefore();
		}

		Object retObj = method.invoke(getSource(), args);

		for (int index = aspectList.size() - 1; index >= 0; index--) {
			aspectList.get(index).doAfter();
		}

		return retObj;
	}

}

測試代碼

public interface Student {
	public void sayHello();
}

import org.aspect.Aspect;

public class StudentAspectOne implements Aspect {

	@Override
	public void doAfter() {
		System.out.println("do After One");

	}

	@Override
	public void doBefore() {
		System.out.println("do Before One");

	}

}

import org.aspect.Aspect;


public class StudentAspectTwo implements Aspect{
	@Override
	public void doAfter() {
		System.out.println("do After Two");

	}

	@Override
	public void doBefore() {
		System.out.println("do Before Two");

	}
}

public class StudentImpl implements Student {

	@Override
	public void sayHello() {
		System.out.println("Student");
	}

}

import java.util.ArrayList;
import java.util.List;

import org.aspect.Aspect;
import org.aspect.DynamicProxyFactory;

public class Test {

	public static void main(String[] args) {

		List<Aspect> aspectList = new ArrayList<Aspect>();

		aspectList.add(new StudentAspectOne());
		aspectList.add(new StudentAspectTwo());
		Student s = (Student)DynamicProxyFactory.newInstance(new StudentImpl(), aspectList);
		s.sayHello();
	}

}

執行Test，控制檯返回

do Before One
do Before Two
Student
do After Two
do After One