【Exception】getReader() has already been called for this request-蒲公英云

【Exception】getReader() has already been called for this request

一、问题描述

1、在SpringMVC的拦截器中，使用了一次 HttpServletRequest 的 getInputStream() 或 getReader() 的方法后，再次在调用，就会抛出异常：

getReader() has already been called for this request

2、最简单的触发：

@RequestMapping(value = "/rankData/mapForm")
    @ResponseBody
    public ResultVO mapForm(HttpServletRequest request) {
        try {
            BufferedReader reader = request.getReader();
            String line ; 
            StringBuffer sb = new StringBuffer();
            while((line=  reader.readLine())!= null) {
                sb.append(line);
            }
            System.out.println("resFrom :" + sb.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            ServletInputStream inputStream = request.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,Charset.defaultCharset()));
            String line ; 
            StringBuffer sb = new StringBuffer();
            while((line=  bufferedReader.readLine())!= null) {
                sb.append(line);
            }
            System.out.println("resFrom222 :" + sb.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return ResultVO.success("");
    }

watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hhSGFfU2ly_size_16_color_FFFFFF_t_70

二、解决思路

1、创建MyHttpServletRequestWrapper 类，继承 HttpServletRequestWrapper，重写 getInputStream 和 getReader 方法

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import org.springframework.util.StreamUtils;
/**
 * description: 重写 MyHttpServletRequestWrapper
 * @version v1.0
 * @author w
 * @date 2021年4月20日下午3:56:53
 **/
public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private byte[] requestBody = null;// 用于将流保存下来
    public MyHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        requestBody = StreamUtils.copyToByteArray(request.getInputStream());
    }
    @Override
    public ServletInputStream getInputStream() throws IOException {
        // 读取 requestBody 中的数据
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(requestBody);
        return new ServletInputStream() {
            @Override
            public int read() throws IOException {
                return byteArrayInputStream.read();
            }
        };
    }
    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }
    /**
     * description: 提供获取requestBody的方法
     * 
     * @return byte[]
     * @version v1.0
     * @author w
     * @date 2021年4月20日 下午4:02:29
     */
    public byte[] getRequestBody() {
        return requestBody;
    }
}

2、创建拦截器：实现对 HttpServletRequestWrapper类的重写

import java.io.IOException;
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;
/**
 * description: RequestBodyFilter
 * @version v1.0
 * @author w
 * @date 2021年4月20日下午4:03:09
 **/
public class RequestBodyFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        System.out.println(RequestBodyFilter.class.getName() + " ---->run");
        ServletRequest requestWrapper = null;
        if (request instanceof HttpServletRequest) {
            requestWrapper = new MyHttpServletRequestWrapper((HttpServletRequest) request);
        }
        if (requestWrapper == null) {
            chain.doFilter(request, response);
        } else {
            chain.doFilter(requestWrapper, response);
        }
    }
    @Override
    public void destroy() {
    }
    @Override
    public void init(FilterConfig arg0) throws ServletException {
    }
}