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初识代理——Proxy
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无处不在的模式——Proxy
最近在看《设计模式之禅》,看到代理模式这一章的时候,发现自己在写spring项目的时候其实很多时候都用到了代理,无论是依赖注入、AOP还是其他,可以说是无处不在。
于是自己便自己摸索写了一些小例子,当然也参考了网上其他博主的博客,毕竟小白一枚hhhhhh
进入正题:
图1-1:代理Proxy
代理模式 现在主流的有两大类:1、JDK代理 2、CGLB代理
(JDK静态代理就不说了,网上很多都有,主要我觉得现在面向企业项目,静态代理局限性有点大,对于我而言可能就只是去了解了一下,而并没有说想要去深入这个)
Th1:JDK动态接口代理(需要实现InvocationHandler接口中的invoke(...)方法,必须实现某个接口)
public class MyJdkProxy implements InvocationHandler {
// 目标对象
public Object target;
// 初始化传入代理对象
public MyJdkProxy(Object target){
this.target = target;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("xsc");
return method.invoke(target,args);
}
public Object newProxy(){
// 获取代理目标对象实例
return Proxy.newProxyInstance(
target.getClass().getClassLoader(),
target.getClass().getInterfaces(),
this
);
}
}
Th2:CGLB动态接口代理(需要实现MethodInterceptor接口中的intercept(...)方法,当然也可无需实现接口,可直接代理类)
public class MyCgljProxy implements MethodInterceptor {
// 目标对象
public Object target;
// 初始化传入代理对象
public MyCgljProxy(Object target){
this.target = target;
}
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
System.out.println("cj");
return methodProxy.invoke(target,objects);
}
public Object newProxy(){
// 获取代理目标对象实例
return Enhancer.create(target.getClass(),this);
}
}
Th3:测试类Test.java
public class Test{
// 需要代理的接口
interface Subject{
void sayHi();
void sayHallo();
}
// 代理接口实现类
static class SubjectImpl implements Subject{
@Override
public void sayHi() {
System.out.println("Hi");
}
@Override
public void sayHallo() {
System.out.println("Hello");
}
}
public static void main(String[] args) {
// JDK动态接口代理方式
Subject target1 = new SubjectImpl();
MyJdkProxy proxy = new MyJdkProxy(target1);
target1 = (Subject) proxy.newProxy();
target1.sayHallo();
target1.sayHi();
System.out.println("----------------------------");
// CGLB动态接口代理方式
Subject target2 = new SubjectImpl();
MyCgljProxy myCgljProxy = new MyCgljProxy(target2);
target2 = (Subject) myCgljProxy.newProxy();
target2.sayHi();
target2.sayHallo();
}
}
Th4:测试结果
public class MyJdkProxy implements InvocationHandler { // 目标对象
public Object target; // 初始化传入代理对象
public MyJdkProxy(Object target){
this.target = target;
} @Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("xsc");
return method.invoke(target,args);
} public Object newProxy(){
// 获取代理目标对象实例
return Proxy.newProxyInstance(
target.getClass().getClassLoader(),
target.getClass().getInterfaces(),
this
);
}
}
public class MyCgljProxy implements MethodInterceptor { // 目标对象
public Object target; // 初始化传入代理对象
public MyCgljProxy(Object target){
this.target = target;
} @Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
System.out.println("cj");
return methodProxy.invoke(target,objects);
} public Object newProxy(){
// 获取代理目标对象实例
return Enhancer.create(target.getClass(),this);
}
}
Th3:测试类Test.java
public class Test{
// 需要代理的接口
interface Subject{
void sayHi();
void sayHallo();
}
// 代理接口实现类
static class SubjectImpl implements Subject{
@Override
public void sayHi() {
System.out.println("Hi");
}
@Override
public void sayHallo() {
System.out.println("Hello");
}
}
public static void main(String[] args) {
// JDK动态接口代理方式
Subject target1 = new SubjectImpl();
MyJdkProxy proxy = new MyJdkProxy(target1);
target1 = (Subject) proxy.newProxy();
target1.sayHallo();
target1.sayHi();
System.out.println("----------------------------");
// CGLB动态接口代理方式
Subject target2 = new SubjectImpl();
MyCgljProxy myCgljProxy = new MyCgljProxy(target2);
target2 = (Subject) myCgljProxy.newProxy();
target2.sayHi();
target2.sayHallo();
}
}
Th4:测试结果
public class Test{
// 需要代理的接口
interface Subject{
void sayHi();
void sayHallo();
} // 代理接口实现类
static class SubjectImpl implements Subject{ @Override
public void sayHi() {
System.out.println("Hi");
} @Override
public void sayHallo() {
System.out.println("Hello");
}
} public static void main(String[] args) {
// JDK动态接口代理方式
Subject target1 = new SubjectImpl();
MyJdkProxy proxy = new MyJdkProxy(target1);
target1 = (Subject) proxy.newProxy(); target1.sayHallo();
target1.sayHi(); System.out.println("----------------------------"); // CGLB动态接口代理方式
Subject target2 = new SubjectImpl();
MyCgljProxy myCgljProxy = new MyCgljProxy(target2);
target2 = (Subject) myCgljProxy.newProxy();
target2.sayHi();
target2.sayHallo();
}
}
总结:
当然这些只是简单的代理,感觉其实一通百通,目的都是为对象提供个代理来控制对其的访问,而我们的代理类则委托预处理、过滤、转发消息,以及委托后进行的后续处理,解决了在直接访问对象时可能带来的问题