經過JDK動態代理實現攔截器

攔截器

攔截器是咱們開發中接觸比較多的。今天使用JDK動態代理模式來實現攔截器。實現過程咱們經過代碼來展現，代碼中有相應的解釋：

//攔截器接口
public interface Interceptor {
    /**
     * 調用真實方法以前執行，寫調用真實方法的前提邏輯
     * @param proxy 代理對象
     * @param obj 真實對象
     * @param method 方法
     * @param args 方法參數
     * @return
     */
    public boolean before(Object proxy,Object obj,Method method,Object[] args);
    /**
     * 當before方法結果是false時，調用此方法
     * @param proxy
     * @param obj
     * @param method
     * @param args
     */
    public void around(Object proxy,Object obj,Method method,Object[] args);
    /**
     * 調用完真實對象或者執行完around方法以後執行此方法
     * @param proxy
     * @param obj
     * @param method
     * @param args
     */
    public void after(Object proxy,Object obj,Method method,Object[] args);
    
}

//攔截器實現類
public class InterceptorImpl implements Interceptor {

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

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

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

//JDK動態代理所須要的接口
public interface ISayHello {
    public void say();
}

//JDK動態代理接口實現類
public class SayHelloImpl implements ISayHello {

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

}

//jdk動態代理實現攔截器
public class InterceptorJdkProxy implements InvocationHandler {
    //真實對象
    private Object obj;
    //攔截器權限定名
    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 {
        //若是沒有攔截器，直接走原邏輯
        if(interceptorClass == null) {
            return method.invoke(obj, args);
        }
        //接收真實對象方法
        Object result = null;
        //反射生成攔截器對象
        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();
    }
}

測試結果展現

當執行before方法返回爲true

當執行before方法返回爲false