返回值输出代理类：这个类主要是为了吧Response里面的返回值获取到，因为直接Response没有提供直接拿到返回值的方法。所以要通过代理来取得返回值

package com.channel.filter;
 
 
import java.io.ByteArrayOutputStream;
import java.io.IOException;
 
import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
 
 
/**
 * 返回值输出代理类
 * 
 * @Title: ResponseWrapper
 * @Description:
 * @author kokJuis
 * @date 上午9:52:11
 */
public class ResponseWrapper extends HttpServletResponseWrapper
{
 
    private ByteArrayOutputStream buffer;
 
    private ServletOutputStream out;
 
    public ResponseWrapper(HttpServletResponse httpServletResponse)
    {
        super(httpServletResponse);
        buffer = new ByteArrayOutputStream();
        out = new WrapperOutputStream(buffer);
    }
 
    @Override
    public ServletOutputStream getOutputStream()
        throws IOException
    {
        return out;
    }
 
    @Override
    public void flushBuffer()
        throws IOException
    {
        if (out != null)
        {
            out.flush();
        }
    }
 
    public byte[] getContent()
        throws IOException
    {
        flushBuffer();
        return buffer.toByteArray();
    }
 
    class WrapperOutputStream extends ServletOutputStream
    {
        private ByteArrayOutputStream bos;
 
        public WrapperOutputStream(ByteArrayOutputStream bos)
        {
            this.bos = bos;
        }
 
        @Override
        public void write(int b)
            throws IOException
        {
            bos.write(b);
        }
 
        @Override
        public boolean isReady()
        {
 
            // TODO Auto-generated method stub
            return false;
 
        }
 
        @Override
        public void setWriteListener(WriteListener arg0)
        {
 
            // TODO Auto-generated method stub
 
        }
    }
 
}

过滤器类：

package com.channel.filter;
 
 
import java.io.IOException;
 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
 
import com.channel.util.RsaEncryptUtil;
 
 
/**
 * 返回值输出过滤器，这里用来加密返回值
 * 
 * @Title: ResponseFilter
 * @Description:
 * @author kokJuis
 * @date 上午9:52:42
 */
public class ResponseFilter implements Filter
{
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
        throws IOException, ServletException
    {
        ResponseWrapper wrapperResponse = new ResponseWrapper((HttpServletResponse)response);//转换成代理类
        // 这里只拦截返回，直接让请求过去，如果在请求前有处理，可以在这里处理
        filterChain.doFilter(request, wrapperResponse);
        byte[] content = wrapperResponse.getContent();//获取返回值
	//判断是否有值
        if (content.length > 0)
        {
 
            String str = new String(content, "UTF-8");
            System.out.println("返回值:" + str);
            String ciphertext = null;
 
            try
            {
                //......根据需要处理返回值
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
		//把返回值输出到客户端
            ServletOutputStream out = response.getOutputStream();
            out.write(ciphertext.getBytes());
            out.flush();
            out.close();
        }
 
    }
 
    @Override
    public void init(FilterConfig arg0)
        throws ServletException
    {
 
    }
 
    @Override
    public void destroy()
    {
 
    }
 
}

启动配置：

 /**
     * 配置过滤器，这里过滤器主要是对返回值做后继处理
     * 
     * @return
     */
    @Bean
    public FilterRegistrationBean someFilterRegistration()
    {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new ResponseFilter());// 配置一个返回值加密过滤器
        registration.addUrlPatterns("/*");
        registration.addInitParameter("paramName", "paramValue");
        registration.setName("responseFilter");
        return registration;
    }

如果是spring mvc 在web.xml下添加配置即可

<!-- 返回值过滤器 -->
	<filter>
		<filter-name>responseFilter</filter-name>
		<filter-class>com.im.filter.ResponseFilter</filter-class>
	</filter>
 
	<filter-mapping>
		<filter-name>responseFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

原文：