通過(guò)JDK動(dòng)態(tài)代理實(shí)現(xiàn)攔截器

gghyoo 發(fā)布于2019-08-15 18:03 / 2400人閱讀

摘要：攔截器攔截器是我們開(kāi)發(fā)中接觸比較多的。今天使用動(dòng)態(tài)代理模式來(lái)實(shí)現(xiàn)攔截器。

攔截器

攔截器是我們開(kāi)發(fā)中接觸比較多的。今天使用JDK動(dòng)態(tài)代理模式來(lái)實(shí)現(xiàn)攔截器。實(shí)現(xiàn)過(guò)程我們通過(guò)代碼來(lái)展示，代碼中有相應(yīng)的解釋：

//攔截器接口
public interface Interceptor {
    /**
     * 調(diào)用真實(shí)方法之前執(zhí)行，寫(xiě)調(diào)用真實(shí)方法的前提邏輯
     * @param proxy 代理對(duì)象
     * @param obj 真實(shí)對(duì)象
     * @param method 方法
     * @param args 方法參數(shù)
     * @return
     */
    public boolean before(Object proxy,Object obj,Method method,Object[] args);
    /**
     * 當(dāng)before方法結(jié)果是false時(shí)，調(diào)用此方法
     * @param proxy
     * @param obj
     * @param method
     * @param args
     */
    public void around(Object proxy,Object obj,Method method,Object[] args);
    /**
     * 調(diào)用完真實(shí)對(duì)象或者執(zhí)行完around方法之后執(zhí)行此方法
     * @param proxy
     * @param obj
     * @param method
     * @param args
     */
    public void after(Object proxy,Object obj,Method method,Object[] args);
    
}

//攔截器實(shí)現(xiàn)類
public class InterceptorImpl implements Interceptor {

    @Override
    public boolean before(Object proxy, Object obj, Method method, Object[] args) {
        System.out.println("反射方法執(zhí)行之前的邏輯~~");
        return false;
    }

    @Override
    public void around(Object proxy, Object obj, Method method, Object[] args) {
        System.out.println("執(zhí)行around方法~~~");
    }

    @Override
    public void after(Object proxy, Object obj, Method method, Object[] args) {
        System.out.println("反射方法之后的邏輯~~");
    }
}

//JDK動(dòng)態(tài)代理所需要的接口
public interface ISayHello {
    public void say();
}

//JDK動(dòng)態(tài)代理接口實(shí)現(xiàn)類
public class SayHelloImpl implements ISayHello {

    @Override
    public void say() {
        System.out.println("真實(shí)對(duì)象邏輯~Hello World!");    
    }

}

//jdk動(dòng)態(tài)代理實(shí)現(xiàn)攔截器
public class InterceptorJdkProxy implements InvocationHandler {
    //真實(shí)對(duì)象
    private Object obj;
    //攔截器權(quán)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;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        //如果沒(méi)有攔截器，直接走原邏輯
        if(interceptorClass == null) {
            return method.invoke(obj, args);
        }
        //接收真實(shí)對(duì)象方法
        Object result = null;
        //反射生成攔截器對(duì)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;
    }
}

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

測(cè)試結(jié)果展示 當(dāng)執(zhí)行before方法返回為true

當(dāng)執(zhí)行before方法返回為false