- 定義一個攔截器的接口
public interface Interceptor {
public boolean before(Object proxy,Object target,Method method,Object[] args);
public void around(Object proxy,Object target,Method method,Object[] args);
public void after(Object proxy,Object target,Method method,Object[] args);
}
這裏定義了3個方法,分別有如下邏輯定義
- before方法返回boolean值,它在真實對象前調用。當返回爲true時,則反射真實對象的方法;當返回爲false時,則調用around方法。
- 在before方法返回爲false時,調用around方法
- 在反射真實對象方法或者around方法執行後,調用after方法
實現這個Interceotor——MyInterceptor
public class MyInterceptor implements Interceptor{
@Override
public boolean before(Object proxy, Object target, Method method, Object[] args) {
System.out.println("反射方法前的邏輯");
return false;
}
@Override
public void around(Object proxy, Object target, Method method, Object[] args) {
System.out.println("取代了被代理對象的方法");
}
@Override
public void after(Object proxy, Object target, Method method, Object[] args) {
System.out.println("反射方法後的邏輯");
}
}
它實現了所有的Interceptor接口方法,使用JDK動態代理,就可以去實現這些方法在是當時的調用邏輯了。
public class InterceptorJdkProxy implements InvocationHandler {
private Object target;//真實對象
private String interceptorClass = null;//攔截器全限定類名
public InterceptorJdkProxy(Object target, String interceptorClass) {
this.target = target;
this.interceptorClass = interceptorClass;
}
public static Object bind(Object target,String interceptorClass) {
return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), new InterceptorJdkProxy(target, interceptorClass));
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if(interceptorClass == null) {
return method.invoke(proxy, args);
}else {
Object result = null;
Interceptor interceptor = (Interceptor) Class.forName(interceptorClass).newInstance();
if(interceptor.before(proxy, target, method, args)) {
result = method.invoke(target, args);
}else {
interceptor.around(proxy, target, method, args);
}
//調用後置方法
interceptor.after(proxy, target, method, args);
return result;
}
}
public static void main(String[] args) {
HelloWorld helloWorld = (HelloWorld) InterceptorJdkProxy.bind(new HelloWorldImpl(), "interceptor.MyInterceptor");
helloWorld.sayHelloWorld();
}
}
上面main方法中的HelloWorld,直接使用了另一篇文章中的對象實現JDK動態代理