动态代理-初级篇

小灰灰 2021-04-17 16:34 412阅读 0赞

最近想总结一下java的动态代理，动态代理有很多种实现方案，下面介绍三种最常用的动态搭理方案：1.jdk自带动态代理2.javassist实现动态代理3.cglib实现动态代理

接口和实现类代码：

````
package com.java.day1.dynamicproxy.one;

public interface Interface {
    void doSomeThing();
}
````

````
package com.java.day1.dynamicproxy.one;

public class RealSubject implements Interface {
    @Override
    public void doSomeThing() {
        System.out.println("do some things..");
    }
}
````

jdk自带动态搭理实现

````
package com.java.day1.dynamicproxy.one;

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

public class JdkProxyHandler implements InvocationHandler {
    //　这个就是我们要代理的真实对象 
    private Object subject;

// 构造方法，给我们要代理的真实对象赋初值 
    public JdkProxyHandler(Object subject) {
        this.subject = subject;
    }

@Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("do otherthings..jdk..");
        return method.invoke(subject, args);
    }
}
````

````
package com.java.day1.dynamicproxy.one;

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

public class JdkTest {
    public static void main(String[] args) {
        //被代理的类 
        RealSubject rs = new RealSubject();
        // 代理增强类 
        InvocationHandler ih = new JdkProxyHandler(rs);
        // 用java反射生成代理类 
        Interface proxy = (Interface) Proxy.newProxyInstance(ih.getClass().getClassLoader(), rs.getClass().getInterfaces(), ih);
        proxy.doSomeThing();
    }
}
````

javassist实现动态代理

````
package com.java.day1.dynamicproxy.one;

import java.lang.reflect.Method;

import javassist.util.proxy.MethodHandler;

public class JavassitInterceptor implements MethodHandler {
    private Object subject;

public JavassitInterceptor(Object subject) {
        this.subject = subject;
    }

@Override
    public Object invoke(Object self, Method m, Method prosess, Object[] args) throws Throwable {
        System.out.println("do other thing..javassist.");
        return m.invoke(subject, args);
    }
}
````

````
package com.java.day1.dynamicproxy.one;

import javassist.util.proxy.ProxyFactory;
import javassist.util.proxy.ProxyObject;

public class javassistTest {
    public static void main(String[] args) throws Exception {
        //被代理的类 
        RealSubject rs = new RealSubject();
        // 代理增强类 
        JavassitInterceptor ih = new JavassitInterceptor(rs);
        // 用javassist反射生成代理类 
        ProxyFactory pf = new ProxyFactory();
        pf.setInterfaces(rs.getClass().getInterfaces());
        Class<?> proxyClass = pf.createClass();
        Interface proxy = (Interface) proxyClass.newInstance();
        ((ProxyObject) proxy).setHandler(ih);
        proxy.doSomeThing();
    }
}
````

cglib实现动态搭理

````
package com.java.day1.dynamicproxy.one;

import java.lang.reflect.Method;

import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class CglibInterceptor implements MethodInterceptor {
    private Object subject;

public CglibInterceptor(Object subject) {
        this.subject = subject;
    }

@Override
    public Object intercept(Object object, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("do other things..cglib...");
        return methodProxy.invoke(subject, objects);
    }
}
````

````
package com.java.day1.dynamicproxy.one;

import net.sf.cglib.proxy.Enhancer;

public class CgligTest {
    public static void main(String[] args) {
        //被代理的类 
        RealSubject rs = new RealSubject();
        // 代理增强类 
        Enhancer enhancer = new Enhancer();
        CglibInterceptor ci = new CglibInterceptor(rs);
        enhancer.setCallback(ci);
        enhancer.setInterfaces(rs.getClass().getInterfaces());
        Interface proxy = (Interface) enhancer.create();
        proxy.doSomeThing();
    }
}
````

我还做了实验，但从创建来看jdk是最快的cglib最慢，但创建好后调用，javassist最快，jdk次之，不过是同一个数量级的，cglib最慢比其他2种慢5倍