代理模式---动态代理之JDK

接口类UserDao：

package com.ant.jdk8.proxy;

public interface UserDao {
    void save();
}

接口类EmployeeDao：

package com.ant.jdk8.proxy;

public interface EmployeeDao {
    void add();
}

目标类UserDaoImpl：

package com.ant.jdk8.proxy;

public class UserDaoImpl implements UserDao {
    @Override
    public void save() {
        System.out.println("保存用户");
    }
}

目标类EmployeeDaoImpl：

package com.ant.jdk8.proxy;

public class EmployeeDaoImpl implements EmployeeDao {
    @Override
    public void add() {
        System.out.println("添加雇员信息");
    }
}

代理类ProxyFactory：

package com.ant.jdk8.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class ProxyFactory {

    //维护一个目标对象
    private Object target;

    public ProxyFactory(Object target){
        this.target = target;
    }

    //生成目标对象的代理对象
    public Object getProxyInstance(){
        return Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                new InvocationHandler(){
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        System.out.println("---开始事务---");
                        Object object = method.invoke(target, args);
                        System.out.println("---提交事务---");
                        return object;
                    }
                });
    }
}

测试类APP：

package com.ant.jdk8.proxy;

public class App {
    public static void main(String[] args) {
        //目标对象
        UserDao target = new UserDaoImpl();
        //代理对象
        UserDao proxy = (UserDao) new ProxyFactory(target).getProxyInstance();
        proxy.save();

        System.out.println("==========================");

        //目标对象
        EmployeeDao target2 = new EmployeeDaoImpl();
        //代理对象
        EmployeeDao proxy2 = (EmployeeDao)new ProxyFactory(target2).getProxyInstance();
        proxy2.add();
    }
}

JDK动态代理总结：

代理对象不需要实现接口，但是目标对象一定要实现接口，否则不能用动态代理。