利用过滤器修改response中的返回值

1. 继承HttpServletResponseWrapper 重新覆盖Response对象,用来获取response中的返回值

package com.example.demo.wrapper;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.*;

public class ResponseWrapper extends HttpServletResponseWrapper {
    private ByteArrayOutputStream buffer = null;
    private ServletOutputStream out = null;
    private PrintWriter writer = null;

    public ResponseWrapper(HttpServletResponse resp) throws IOException {
        super(resp);
        buffer = new ByteArrayOutputStream();// 真正存储数据的流
        out = new WapperedOutputStream(buffer);
        writer = new PrintWriter(new OutputStreamWriter(buffer));
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return out;
    }

    @Override
    public PrintWriter getWriter() throws UnsupportedEncodingException {
        return writer;
    }

    @Override
    public void flushBuffer() throws IOException {
        if (out != null) {
            out.flush();
        }
        if (writer != null) {
            writer.flush();
        }
    }

    @Override
    public void reset() {
        buffer.reset();
    }

    public byte[] getResponseData() throws IOException {
        flushBuffer();
        return buffer.toByteArray();
    }

    public String getContent() throws IOException {
        flushBuffer();
        return buffer.toString();
    }


    private class WapperedOutputStream extends ServletOutputStream {
        private ByteArrayOutputStream bos = null;

        public WapperedOutputStream(ByteArrayOutputStream stream) throws IOException {
            bos = stream;
        }

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

        @Override
        public void write(byte[] b) throws IOException {
            bos.write(b, 0, b.length);
        }

        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            bos.write(b, off, len);
        }

        @Override
        public boolean isReady() {
            return false;
        }

        @Override
        public void setWriteListener(WriteListener writeListener) {

        }
    }
}

2、创建过滤器，修改response中的内容，返回

package com.example.demo.filter;

import com.example.demo.wrapper.ResponseWrapper;
import org.apache.commons.lang.StringUtils;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;

@Component
public class ResponseFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        ResponseWrapper responseWrapper = new ResponseWrapper((HttpServletResponse) servletResponse);
        filterChain.doFilter(servletRequest, responseWrapper);
        String contentType = responseWrapper.getContentType();
        byte[] content = responseWrapper.getResponseData();
        String str="";
        if (StringUtils.isNotBlank(contentType) && (contentType.contains(MediaType.APPLICATION_JSON_VALUE) || contentType.contains(MediaType.TEXT_HTML_VALUE))) {
           str = new String(content);
            str=str+"xiaoming";
            System.out.println("filter:"+str);
            HttpServletResponse response=(HttpServletResponse)servletResponse;
            writeResponse(response,200,str);
        }
    }
    public static void writeResponse(HttpServletResponse response, int status, String json) {
        try {
            response.reset();//很重要
            response.setHeader("Access-Control-Allow-Origin", "*");
            response.setHeader("Access-Control-Allow-Methods", "*");
            response.setContentType("application/json;charset=UTF-8");
            response.setStatus(status);
            response.getWriter().write(json);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3、配置过滤器

package com.example.demo.config;

import com.example.demo.filter.ResponseFilter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;

import java.util.ArrayList;
import java.util.List;

@SpringBootConfiguration
public class FilterConfig {
    @Autowired
   private ResponseFilter  responseFilter;
    @Bean
    public FilterRegistrationBean getFilterConfig(){
        FilterRegistrationBean filterRegistrationBean=new FilterRegistrationBean();
        filterRegistrationBean.setFilter(responseFilter);
        List<String> filterList=new ArrayList<>();
        filterList.add("/*");
        filterRegistrationBean.setUrlPatterns(filterList);
        return filterRegistrationBean;
    }


}