JAVA动态代理模式

这是我要实现的效果

 

 

public static void main(String[] args) {
		UserDao proxy  = (UserDao)   BeanProxyFactory.getProxyObject(UserDaoImpl.class.getName());
		proxy.save(new User());//我想实现保存的时候，自动调用一些动作
	} 

 

 

看代码

 

 

package org.dao;

import org.pojo.User;

public interface UserDao {
	public void save(User user);
	public void update(User user);

}

 

package org.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(value = RetentionPolicy.RUNTIME)
public @interface Transaction {
}

 

package org.dao.impl;

import org.annotation.Transaction;
import org.dao.UserDao;
import org.pojo.User;

@Transaction
public class UserDaoImpl implements UserDao {

	public void save(User user) {
		System.out.println("save user!" + user.getUserId());
	}

	public void update(User user) {
		System.out.println("save user!" + user.getUserId());
	}

}

 

package org.aop;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.HashSet;
import java.util.Set;

import org.annotation.Transaction;


public class MethodInvocationHandler implements InvocationHandler {
	private Object originalObject;
	private Set<String> transactionMethod = new HashSet<String>();

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		Object result = null;

		if (transactionMethod.contains(method.getName())) {
			System.out.println("事务开启");
			result = method.invoke(originalObject, args);
			System.out.println("事务结束");
		} else {
			result = method.invoke(originalObject, args);
		}
		return result;
	}

	public MethodInvocationHandler(Object originalObject) {
		this.originalObject = originalObject;
		for (Method m : originalObject.getClass().getMethods()) {
			if (m.isAnnotationPresent(Transaction.class)
					|| originalObject.getClass().isAnnotationPresent(
							Transaction.class)) {
				this.transactionMethod.add(m.getName());
			}
		}
	}
}

 

package org.aop;

import java.lang.reflect.Proxy;
import org.dao.UserDao;
import org.dao.impl.UserDaoImpl;
import org.pojo.User;

public class BeanProxyFactory {
	public static Object getProxyObject(String className) {
		Object proxyObject = null;
		try {
			Class claszz = Class.forName(className);
			MethodInvocationHandler handler = new MethodInvocationHandler(
					claszz.newInstance());
			proxyObject = Proxy.newProxyInstance(claszz.getClassLoader(),
					claszz.getInterfaces(), handler);
		} catch (Exception e) {
		}
		return proxyObject;
	}

	public static void main(String[] args) {
		UserDao proxy = (UserDao) BeanProxyFactory
				.getProxyObject(UserDaoImpl.class.getName());
		proxy.save(new User());// 我想实现保存的时候，自动调用一些动作
	}
}