Spring MVC 使用 HttpServletResponseWrapper 修改返回结果

HttpServletResponseWrapper 是什么?
　　ServletResponse 的包装类，相关设计模式 装饰者模式。

运行环境
　　jdk 1.7
　　spring boot 整合的web环境

关键代码
Wrapper

package com.basic.m.web.config;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

public class CustomizeResponseWrapper extends HttpServletResponseWrapper {

    private ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    private PrintWriter printWriter = new PrintWriter(outputStream);

    public CustomizeResponseWrapper(HttpServletResponse response) {
        super(response);
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        return printWriter;
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return new ServletOutputStream() {
            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setWriteListener(WriteListener listener) {

            }

            @Override
            public void write(int b) throws IOException {
                outputStream.write(b);
            }
        };
    }

    public void flush(){
        try {
            printWriter.flush();
            printWriter.close();
            outputStream.flush();
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public ByteArrayOutputStream getByteArrayOutputStream(){
        return outputStream;
    }

    public String getTextContent() {
        flush();
        return outputStream.toString();
    }
}

Filter

 package com.basic.m.web.config;

 import com.alibaba.fastjson.JSONObject;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.core.annotation.Order;

 import javax.servlet.*;
 import javax.servlet.annotation.WebFilter;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;

 @Order(2)
 @WebFilter(urlPatterns = "/*", filterName = "responseFilter")
 public class ResponseFilter implements Filter {
     private static final Logger logger = LoggerFactory.getLogger(ResponseFilter.class);

     @Override
     public void init(FilterConfig filterConfig) throws ServletException {
         logger.info("enter ResponseFilter init method");
     }

     @Override
     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
         logger.info("enter ResponseFilter doFilter method");
         CustomizeResponseWrapper responseWrapper = new CustomizeResponseWrapper((HttpServletResponse) response);
         chain.doFilter(request, responseWrapper);

         System.out.println(responseWrapper.getTextContent());

       /*  MyResponseWrapper responseWrapper = new MyResponseWrapper((HttpServletResponse) response);
         chain.doFilter(request, responseWrapper);*/

         System.out.println(responseWrapper.getTextContent());

         String content = responseWrapper.getTextContent();
         JSONObject resultJson = new JSONObject();
         resultJson.put("code", "ok");
         resultJson.put("msg", "success");
         resultJson.put("result", content);

         response.setContentLength(resultJson.toJSONString().length());
         response.setContentType("application/json;charset=utf-8");
         ((HttpServletResponse) response).setStatus(203);
         response.getOutputStream().write(resultJson.toJSONString().getBytes());
     }

     @Override
     public void destroy() {

     }
 }

参考

　　通过百度和google 零零散散的查询相关代码后自己实现了一个，这里需要特别注意的是网络上搜索出来的大部分结果都是通过重写 getWriter() 方法来写入流。这里我一直搞不明白为什么。因为个人调试时用于都只会进入 getOutputStream() 方法来写入流。