Java代理

对于诸如以下代码，代理可以实现在不改变原有实现逻辑的情况下，对代码增加修饰内容。

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public interface Subject {
  void request();
  void hello();
}

public class RealSubject implements Subject {

    @Override
    public void request() {        
      System.out.println("real subject execute request");
    }

    @Override
    public void hello() {        
      System.out.println("real subject execute hello");
    }
}

静态代理

以下为静态代理的实现方式。

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public class Proxy implements Subject {
    private RealSubject realSubject;

    public Proxy(RealSubject realSubject) {
        this.realSubject = realSubject;
    }

    @Override
    public void request() {        
      System.out.println("before");
        try {
            realSubject.request();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {            
          System.out.println("after");
        }
    }

    @Override
    public void hello() {        realSubject.hello();
    }
}

动态代理

静态代理的缺点，每当

JDK实现动态代理

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

public class JdkProxySubject implements InvocationHandler {
    private RealSubject realSubject;//此处为实际被代理的Class

    public JdkProxySubject(RealSubject realSubject) {
        this.realSubject = realSubject;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {        
        System.out.println("before");
        Object result = null;
        try {
            result = method.invoke(realSubject, args);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            System.out.println("after");
        }
        return result;
    }
}

CGLIB实现动态代理

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import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;

public class DemoMethodInterceptor implements MethodInterceptor {    
    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {        
      System.out.println("before in cglib");
        Object result = null;
        try {
            result = methodProxy.invokeSuper(obj, args);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            System.out.println("after in cglib");
        }
        return result;
    }
}