拦截器

拦截器是我们开发中接触比较多的。今天使用JDK动态代理模式来实现拦截器。实现过程我们通过代码来展示，代码中有相应的解释：

//拦截器接口
public interface Interceptor {/*** 调用真实方法之前执行，写调用真实方法的前提逻辑* @param proxy 代理对象* @param obj 真实对象* @param method 方法* @param args 方法参数* @return*/public boolean before(Object proxy,Object obj,Method method,Object[] args);/*** 当before方法结果是false时，调用此方法* @param proxy* @param obj* @param method* @param args*/public void around(Object proxy,Object obj,Method method,Object[] args);/*** 调用完真实对象或者执行完around方法之后执行此方法* @param proxy* @param obj* @param method* @param args*/public void after(Object proxy,Object obj,Method method,Object[] args);}

//拦截器实现类
public class InterceptorImpl implements Interceptor {@Overridepublic boolean before(Object proxy, Object obj, Method method, Object[] args) {System.out.println("反射方法执行之前的逻辑~~");return false;}@Overridepublic void around(Object proxy, Object obj, Method method, Object[] args) {System.out.println("执行around方法~~~");}@Overridepublic void after(Object proxy, Object obj, Method method, Object[] args) {System.out.println("反射方法之后的逻辑~~");}
}

//JDK动态代理所需要的接口
public interface ISayHello {public void say();
}

//JDK动态代理接口实现类
public class SayHelloImpl implements ISayHello {@Overridepublic void say() {System.out.println("真实对象逻辑~Hello World!");    }}

//jdk动态代理实现拦截器
public class InterceptorJdkProxy implements InvocationHandler {//真实对象private Object obj;//拦截器权限定名private String interceptorClass = null;public Object bind(Object obj,String interceptorClas) {this.obj = obj;this.interceptorClass = interceptorClas;Object proxy = Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), this);return proxy;}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {//如果没有拦截器，直接走原逻辑if(interceptorClass == null) {return method.invoke(obj, args);}//接收真实对象方法Object result = null;//反射生成拦截器对象Interceptor interceptor = (Interceptor) Class.forName(interceptorClass).newInstance();if(interceptor.before(proxy, obj, method, args)) {result = method.invoke(obj, args);} else {interceptor.around(proxy, obj, method, args);}interceptor.after(proxy, obj, method, args);return result;}
}

//测试代码
public class TestInterceptor {public static void main(String[] args) {InterceptorJdkProxy interceptorJdkProxy = new InterceptorJdkProxy();ISayHello bind = (ISayHello) interceptorJdkProxy.bind(new SayHelloImpl(), "interceptor.InterceptorImpl");bind.say();}
}

测试结果展示

当执行before方法返回为true

当执行before方法返回为false