动态代理中存在的概念

目标类、目标对象【target】
代理类、代理对象【proxy】
增强逻辑【advice】

JDK动态代理

要求：目标类必须要实现接口
原理：和目标类实现同一个接口，对目标类进行增强

代理工厂【ProxyFactory】实现【InvocationHandler】

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;public class ProxyFactory<T> implements InvocationHandler {// 目标对象private final T target;public ProxyFactory(T target) {this.target = target;}/*** 获取代理对象*/@SuppressWarnings("all")public T getProxy() {// 类加载器ClassLoader classLoader = getClassLoader();// 接口Class<?>[] interfaces = getInterfaces(target);// 返回代理对象return (T) Proxy.newProxyInstance(classLoader, interfaces, this);}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {Object obj;try {// 前置增强before();obj = method.invoke(target, args);// 返回后增强afterReturning();return obj;} catch (Throwable throwable) {// 异常后增强afterThrowing();throw throwable;} finally {// 后置增强after();}}private ClassLoader getClassLoader() {return Thread.currentThread().getContextClassLoader();}private Class<?>[] getInterfaces(T target) {return target.getClass().getInterfaces();}private void before() {System.out.println("before...");}private void after() {System.out.println("after...");}private void afterThrowing() {System.out.println("afterThrowing...");}private void afterReturning() {System.out.println("afterReturning...");}
}

目标类的接口【TargetInterface】

public interface TargetInterface {void method();
}

目标类【Target】实现了接口

public class Target implements TargetInterface {public void method() {System.out.println("执行目标方法...");}
}

测试类【JDKDynamicProxyTest】

/*** 测试JDK动态代理*/
public class JDKDynamicProxyTest {public static void main(String[] args) {// 目标对象TargetInterface target = new Target();ProxyFactory<TargetInterface> proxyFactory = new ProxyFactory<>(target);// 代理对象TargetInterface proxy = proxyFactory.getProxy();// 目标对象方法执行逻辑 + 增强逻辑proxy.method();}
}

CGLIB动态代理

要求：目标类非final关键字修饰
原理：将目标类作为父类，通过子类来对父类进行增强

添加Maven依赖

<!--CGLIB依赖-->
<dependency><groupId>cglib</groupId><artifactId>cglib</artifactId><version>3.3.0</version>
</dependency>

代理工厂【ProxyFactory】实现【MethodInterceptor】

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;import java.lang.reflect.Method;public class ProxyFactory<T> implements MethodInterceptor {/*** 获取代理对象*/@SuppressWarnings("all")public T getProxy(Class<T> cls) {Enhancer enhancer = new Enhancer();// 设置父类enhancer.setSuperclass(cls);// 设置回调enhancer.setCallback(this);// 返回创建的代理对象return (T) enhancer.create();}@Overridepublic Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {Object result;try {System.out.println("前置增强...");// 调用目标对象的方法result = methodProxy.invokeSuper(o, args);System.out.println("正常返回时增强...");return result;} catch (Throwable throwable) {System.out.println("异常时增强...");throw throwable;} finally {System.out.println("后置增强...");}}
}

目标类【Target】没有实现接口

public class Target {public void method() {System.out.println("目标方法执行++++++++");}
}

测试类【CGLIBDynamicProxyTest】

public class CGLIBDynamicProxyTest {public static void main(String[] args) {ProxyFactory<Target> proxyFactory = new ProxyFactory<>();// 代理对象Target proxy = proxyFactory.getProxy(Target.class);// 原始逻辑 + 增强逻辑proxy.method();}
}