Java中的一些代理技术

使用cglib,asm 对接口进行拦截,这里需要调用Invoke方法

        final IUserService userService=new UserService();

        

        Enhancer enhancer=new Enhancer();

        enhancer.setSuperclass(IUserService.class);

        enhancer.setCallback(new MethodInterceptor() {

            

            @Override

            public Object intercept(Object arg0, Method arg1, Object[] arg2,

                    MethodProxy arg3) throws Throwable {

                System.out.println(arg1.getName());

                

                return arg3.invoke(userService, arg2);

            }

        });

        IUserService proxy= (IUserService) enhancer.create();

        System.out.println(proxy.getNameById(3));

View Code

        final IUserService userService=new UserService();

        

        Enhancer enhancer=new Enhancer();

        enhancer.setSuperclass(UserService.class);

        enhancer.setCallback(new MethodInterceptor() {

            

            @Override

            public Object intercept(Object arg0, Method arg1, Object[] arg2,

                    MethodProxy arg3) throws Throwable {

                System.out.println(arg1.getName());

                

                return arg3.invoke(userService, arg2);

            }

        });

        IUserService proxy= (IUserService) enhancer.create();

        System.out.println(proxy.getNameById(3));

View Code

 
拦截一些自开发类(自己控制类的创建)，非其他框架生成的，就不需要代理中引用的Target了

        Enhancer enhancer=new Enhancer();

        enhancer.setSuperclass(UserService.class);

        enhancer.setCallback(new MethodInterceptor() {

            

            @Override

            public Object intercept(Object arg0, Method arg1, Object[] arg2,

                    MethodProxy arg3) throws Throwable {

                System.out.println(arg1.getName());

                

                return arg3.invokeSuper(arg0, arg2);

            }

        });

        IUserService proxy= (IUserService) enhancer.create();

        System.out.println(proxy.getNameById(3));

View Code

 使用动态代理,只支持接口

        final IUserService userService=new UserService();

       IUserService proxy2=(IUserService) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{ IUserService.class}, new InvocationHandler() {

            

            @Override

            public Object invoke(Object proxy, Method method, Object[] args)

                    throws Throwable {

                    System.out.println(method.getName());

                    return method.invoke(userService, args);

            }

        });

View Code

 使用Enhancer与动态代理，拦截Request，注意Enhancer需要设置类加载器

package cn.haoda.web.filter;



import java.io.IOException;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;



import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;



import cn.haoda.web.filter.imp.UserService;



import net.sf.cglib.proxy.Enhancer;

import net.sf.cglib.proxy.MethodInterceptor;

import net.sf.cglib.proxy.MethodProxy;



/**

 * Servlet Filter implementation class Filter1

 */

public class Filter1 implements Filter {



    /**

     * Default constructor. 

     */

    public Filter1() {

        // TODO Auto-generated constructor stub

    }



    /**

     * @see Filter#destroy()

     */

    public void destroy() {

        // TODO Auto-generated method stub

    }



    /**

     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)

     */

    public void doFilter(final ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {

        // TODO Auto-generated method stub

        // place your code here



        // pass the request along the filter chain

        

        final HttpServletRequest request = (HttpServletRequest) req;

        HttpServletResponse response = (HttpServletResponse) resp;

        

    

        

        Enhancer enhancer=new Enhancer();

        enhancer.setSuperclass(HttpServletRequest.class);

        enhancer.setClassLoader(this.getClass().getClassLoader()); //需要指定这句不然会报错

        enhancer.setCallback(new MethodInterceptor() {

            

            @Override

            public Object intercept(Object arg0, Method arg1, Object[] arg2,

                    MethodProxy arg3) throws Throwable {

                System.out.println("Enhancer->" +arg1.getName());

                

                return arg3.invoke(request, arg2);

            }

        });

    

        

        ServletRequest proxyReq=(ServletRequest) Proxy.newProxyInstance(this.getClass().getClassLoader(), request.getClass().getInterfaces(), new InvocationHandler() {

            

            @Override

            public Object invoke(Object proxy, Method method, Object[] args)

                    throws Throwable {

                System.out.println("动态代理->" +method.getName());

                return method.invoke(request, args);

            }

        });

        

        chain.doFilter((HttpServletRequest)enhancer.create(), response);

        //chain.doFilter(proxyReq, response);

    }



    /**

     * @see Filter#init(FilterConfig)

     */

    public void init(FilterConfig fConfig) throws ServletException {

        // TODO Auto-generated method stub

    }



}

View Code

 

参考：
http://llying.iteye.com/blog/220452
http://stackoverflow.com/questions/11574049/cglib-with-spring-throws-illegalaccesserror
关于类加载器:http://www.ibm.com/developerworks/cn/java/j-lo-classloader/