关于SSM框架的那些事（三）------动态代理模式（拦截器）

1.使用拦截器的简单demo

1.1真实对象

public interface HelloWord {
    public void sayHello();
}

/**
 * @author wfb
 * @date 2020/3/25 20:28
 */
public class HelloWordImpl implements HelloWord {
    @Override
    public void sayHello() {
        System.out.println("helloWord");
    }
}

1.2拦截器接口与实现

import java.lang.reflect.Method;

/**
 * @author wfb
 * @date 2020/3/25 20:29
 */
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);
}

/**
 * @author wfb
 * @date 2020/3/25 20:31
 */
public class MyInterceptor implements Interceptor {
    @Override
    public boolean before(Object proxy, Object target, Method method, Object[] args) {
        System.err.println("执行前的方法");
        return true;
    }

    @Override
    public void around(Object proxy, Object target, Method method, Object[] args) {
        System.err.println("环绕");
    }

    @Override
    public void after(Object proxy, Object target, Method method, Object[] args) {
        System.err.println("执行后的方法");
    }
}

1.3代理对象

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * @author wfb
 * @date 2020/3/25 20:33
 */
public class JdkInterceptorExample implements InvocationHandler {

    //真实对象
    private Object target = null;
    //拦截器全限定名
    private String classInterceptor = null;

    public JdkInterceptorExample(Object target,String classInterceptor){
        this.target = target;
        this.classInterceptor = classInterceptor;
    }

    public static Object bind(Object target,String classInterceptor){
        return Proxy.newProxyInstance(target.getClass().getClassLoader(),target.getClass().getInterfaces(),
                new JdkInterceptorExample(target,classInterceptor));
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        //如果没有设置拦截器，直接通过代理对象执行真实对象方法
        if (classInterceptor==null){
            return method.invoke(target,args);
        }
        Object result = null;
        //通过反射生成拦截器
        Interceptor interceptor = ((Interceptor) Class.forName(classInterceptor).newInstance());
        if(interceptor.before(proxy,target,method,args)){
            result = method.invoke(target,args);
        }
        else{//返回false执行around方法
            interceptor.around(proxy,target,method,args);
        }
        //调用后置方法
        interceptor.after(proxy,target,method,args);

        return result;
    }
}

1.4调用者

/**
 * @author wfb
 * @date 2020/3/25 20:46
 */
public class InterceptorDemo {
    public static void main(String[] args){
        HelloWord proxy = ((HelloWord) JdkInterceptorExample.bind(new HelloWordImpl(),
                "com.javababy.test.MyInterceptor"));
        proxy.sayHello();
    }
}

1.5 结果

"C:\Program Files\Java\jdk1.8.0_144\bin\java.exe" "-javaagent:D:\IntelliJ IDEA 2018.1.5\lib\idea_rt.jar=51142:D:\IntelliJ IDEA 2018.1.5\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_144\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_144\jre\lib\rt.jar;E:\idea_workspace\interceptor-jdk\out\production\interceptor-jdk" com.javababy.test.InterceptorDemo
执行前的方法
helloWord
执行后的方法

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