java反射回顾<四>

jdk动态代理

//动物接口public interface Animal {    void shout(String sound);}

//动物接口实现类public class Cat implements Animal {    @Override    public void shout(String sound) {        for (int i = 0; i < 3; i++) {            System.out.print("cat->"+sound + "! ");        }        System.out.println();    }}

//动物接口实现类public class Dog implements Animal {    @Override    public void shout(String sound) {        for (int i = 0; i < 3; i++) {            System.out.print("dog->"+sound + "! ");        }        System.out.println();    }}

class AnimalProxy implements InvocationHandler {    private Object target;    public Object getInstance(Object target) {        this.target = target;        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);    }    @Override    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {        Object result = null;        System.out.println("方法调用前...");        result = method.invoke(target, args);        System.out.println("方法调用后...");        return result;    }}

public class ProxyTest {    public static void main(String[] args) {        AnimalProxy proxy=new AnimalProxy();        Animal dogProxy= (Animal) proxy.getInstance(new Dog());        dogProxy.shout("wang");    }}

cglib动态代理

JDK动态代理机制缺陷:JDK的动态代理机制只能代理实现了接口的类，而不能实现接口的类就不能实现JDK的动态代理

cglib是针对类来实现代理的，他的原理是对指定的目标类生成一个子类，并覆盖其中方法实现增强，

cglib缺陷 cglib实现动态代理但因为采用的是继承，所以不能对final修饰的类进行代理。

class Snake {    public void makeSound(String name) {        System.out.println("Hi," + name + "");    }}class AnimalProxyCglib implements MethodInterceptor {    private Object target;    public Object getInstance(Object target) {        this.target = target;        Enhancer enhancer = new Enhancer();        enhancer.setSuperclass(this.target.getClass());        enhancer.setCallback(this);        return enhancer.create();    }    @Override    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {        Object result = null;        System.out.println("方法调用前操作...");        result = methodProxy.invokeSuper(o, objects);        System.out.println("方法调用后操作...");        return result;    }}public class DynamicProxyCglibDemo {    public static void main(String[] args) {        AnimalProxyCglib proxy = new AnimalProxyCglib();        Snake dogProxy=(Snake)proxy.getInstance(new Snake());        dogProxy.makeSound("tom");    }}

RPC利用动态代理调用远程函数

HelloService helloService=rpcProxy.create(HelloService.class);

客户端需要调用远程一个服务对象的时候,通过动态代理的方式创建客户端所需的对象

public <T> T create(final Class<?> interfaceClass, final String serviceVersion) {        return (T) Proxy.newProxyInstance(interfaceClass.getClassLoader(), new Class<?>[]{interfaceClass}, new InvocationHandler() {            @Override            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                //创建RPC请求对象，并设置请求属性                RpcRequest request = new RpcRequest();                request.setRequestId(UUID.randomUUID().toString());                request.setInterfaceName(method.getDeclaringClass().getName());                request.setMethodName(method.getName());                request.setParameterTypes(method.getParameterTypes());                request.setServiceVersion(serviceVersion);                request.setParameter(args);                //获取Rpc服务地址                if (serviceDiscovery != null) {                    String serviceName = interfaceClass.getName();                    if (StringUtil.isNotEmpty(serviceVersion)) {                        serviceName += "-"+serviceVersion;                    }                    serviceAddress = serviceDiscovery.discover(serviceName);                    LOGGER.debug("discover service:{}=>", serviceName, serviceVersion);                }                if (StringUtil.isEmpty(serviceAddress)) {                    throw new RuntimeException("service address is empty ");                }                //从rpc服务地址中解析主机名与对应的端口号                String[] array = StringUtil.split(serviceAddress, ":");                String host = array[0];                int port = Integer.parseInt(array[1]);                //创建rpc客户端对象并且发送rpc请求                RpcClient client = new RpcClient(host, port);                long beginTime = System.currentTimeMillis();                RpcResponse response = client.send(request);                LOGGER.debug("time:{}ms", System.currentTimeMillis() - beginTime);                if (response == null) {                    throw new RuntimeException("response is null ");                }                if (response.hasException()) {                    throw response.getException();                } else {                    return response.getResult();                }            }        });    }