java 动态代理

动态代理就是通过反射来生成一个代理

在java中java.lang.reflect包下提供了一个Proxy类和一个InvocationHandler接口,通过这个类和接口就可以生成动态代理对象.JDK提供的代理只能针对接口做代理.我们有更强大的代理cglib,Proxy类中的方法创建动态代理对象

Student.java

public interface Student {
	public void login();
	
	public void submit();
}

StudentImp.java

public class StudentImp implements Student {

	@Override
	public void login() {
		System.out.println("登录");
	}

	@Override
	public void submit() {
		System.out.println("提交");
	}

}

User.java

public interface User {
	public void add();
	
	public void delete();
}

UserImp.java

public class UserImp implements User {

	@Override
	public void add() {
		//System.out.println("权限校验");
		System.out.println("添加功能");
		//System.out.println("日志记录");
	}

	@Override
	public void delete() {
		//System.out.println("权限校验");
		System.out.println("删除功能");
		//System.out.println("日志记录");
	}

}

MyInvocationHandler.java

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

public class MyInvocationHandler implements InvocationHandler {
	private Object target;
	
	public MyInvocationHandler(Object target) {
		this.target = target;
	}
	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		System.out.println("权限校验");
		method.invoke(target, args);					//执行被代理target对象的方法 
		System.out.println("日志记录");
		return null;
	}

}

Test.java

import java.lang.reflect.Proxy;

public class Test {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		/*UserImp ui = new UserImp();
		ui.add();
		ui.delete();
		
		System.out.println("-------------------------------");*/
		/*
		 * public static Object newProxyInstance(ClassLoader loader,Class[] interfaces,
		 * InvocationHandler h)
		 */
		/*MyInvocationHandler m = new MyInvocationHandler(ui);
		User u = (User)Proxy.newProxyInstance(ui.getClass().getClassLoader(), ui.getClass().getInterfaces(), m);
		u.add();
		u.delete();*/
		
		StudentImp si = new StudentImp();
		si.login();
		si.submit();
		
		System.out.println("-------------------------------");
		MyInvocationHandler m = new MyInvocationHandler(si);
		Student s = (Student)Proxy.newProxyInstance(si.getClass().getClassLoader(), si.getClass().getInterfaces(), m);
		
		s.login();
		s.submit();
	}

}