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

浅浅的花香味﹌ 2023-01-18 13:20 72阅读 0赞

## 【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 {
    		
    	}
    }

3、[配置过滤器][Link 1]，略。

**三、总结**

1、经过测试，分别调用： request.getReader() 和 request.getInputStream() 方法多次，没有遇到异常信息。

2、遇到 request.getInputStream() 只能调用一次的问题，咋办呢？ 重写一个HttpServletRequestWrapper 方法， 增加过滤器进行配置，即可。

参考资料： [Spring Boot 添加过滤器][Link 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hhSGFfU2ly_size_16_color_FFFFFF_t_70]: /images/20221021/400a4d286ddb4783a619029d341a5af3.png
[Link 1]: https://thinkcode.blog.csdn.net/article/details/114521445