解决HttpServletRequest InputStream（错误提示Request body missin ）只能使用一次的问题

通常我只定义一个拦截器，对请求参数处理的时候，尤其是对post需要用到流，那这样处理完后跑到控制器那边就会报request body missing

错误提示：
流已经关闭，因为如果通过过滤拦截器读取流的话，IO流关闭只能读取一次，即使不关闭的话，流有个read标志位，后续控制器会从read标志位开始读，读过流之后就读取不到数据了，除非利用void reset()方法，把pos位置位开始，重新读，但是不是任何流都可以使用，所以我们写通用的方法时候，读取完流中数据之后，需要进行包装request，将流重新写入，供后续控制器读取。

网络上解释如下：
那是因为流对应的是数据，数据放在内存中，有的是部分放在内存中。read 一次标记一次当前位置（mark position），第二次read就从标记位置继续读（从内存中copy）数据。所以这就是为什么读了一次第二次是空了。怎么让它不为空呢？只要inputstream 中的pos 变成0就可以重写读取当前内存中的数据。javaAPI中有一个方法public void reset() 这个方法就是可以重置pos为起始位置，但是不是所有的IO读取流都可以调用该方法！ServletInputStream是不能调用reset方法，这就导致了只能调用一次getInputStream()。

解决方法

1.自定义一个request

package com.zhongyun.zycx.utils;import org.springframework.util.StreamUtils;import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;/*** @author lc* @version 1.0* @date 2021/10/27 10:27*/
public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {private final byte[] body;private String bodyString;public MyHttpServletRequestWrapper(HttpServletRequest request) throws IOException {super(request);this.bodyString = StreamUtils.copyToString(request.getInputStream(), Charset.forName("UTF-8"));body = bodyString.getBytes("UTF-8");}@Overridepublic BufferedReader getReader() throws IOException {return new BufferedReader(new InputStreamReader(getInputStream()));}@Overridepublic ServletInputStream getInputStream() throws IOException {final ByteArrayInputStream bais = new ByteArrayInputStream(body);return new ServletInputStream() {@Overridepublic boolean isFinished() {return false;}@Overridepublic boolean isReady() {return false;}@Overridepublic void setReadListener(ReadListener readListener) {}@Overridepublic int read() throws IOException {return bais.read();}};}}

写一个过滤器

一定要在启动类上加@ServletComponentScan(“com.zhongyun.zycx.handler”)

package com.zhongyun.zycx.handler;import com.zhongyun.zycx.utils.MyHttpServletRequestWrapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;@WebFilter(urlPatterns = "/*",filterName = "channelFilter")
public class ChannelFilter implements Filter {private Logger logger = LoggerFactory.getLogger(ChannelFilter.class);@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {logger.info("================进入过滤器======================");// 防止流读取一次后就没有了, 所以需要将流继续写出去filterChain.doFilter(new MyHttpServletRequestWrapper((HttpServletRequest) servletRequest), servletResponse);}@Overridepublic void destroy() {}
}

拦截器

package com.zhongyun.zycx.handler;import net.sf.json.JSONObject;
import org.springframework.web.servlet.HandlerInterceptor;
import weixin.popular.util.StreamUtils;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.nio.charset.Charset;/*** @author lc* @version 1.0* @date 2021/10/26 14:51*/
public class TicketsInterceptor implements HandlerInterceptor {@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {crossDomain(request,response); // 设置请求头，解决跨域问题String word = "测试";String method = request.getMethod();if ("GET".equals(method)) {if (request.getParameter("word") != null) {word = request.getParameter("word");}}if ("POST".equals(method)) {String paramstr = StreamUtils.copyToString(request.getInputStream(), Charset.defaultCharset());JSONObject jsonObject = JSONObject.fromObject(paramstr);if (jsonObject.containsKey("word")) {word = jsonObject.getString("word");}}if (word == null || word.length() < 2) {response.setStatus(500, "word最少为2位");return false;}System.out.println("释放拦截器");return true;}// 跨域public void crossDomain(HttpServletRequest request, HttpServletResponse response) {response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));response.setHeader("Access-Control-Allow-Credentials", "true");}
}

拦截器配置

package com.zhongyun.zycx.handler;import org.aopalliance.intercept.Interceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.InterceptorRegistration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;/*** 拦截器的配置** @author lc* @version 1.0* @date 2021/10/26 14:58*/
@Configuration//标识这是一个配置类
public class InterceptorConfiguration implements WebMvcConfigurer {// 拦截路径@Overridepublic void addInterceptors(InterceptorRegistry registry) {//注册Interceptor拦截器(Interceptor这个类是我们自己写的拦截器类)InterceptorRegistration registration = registry.addInterceptor(new TicketsInterceptor());//addPathPatterns()方法添加需要拦截的路径registration.addPathPatterns("/openapi/**");      //路径都被拦截//excludePathPatterns()方法添加不拦截的路径registration.excludePathPatterns(                         //添加不拦截路径"/demo/loginPage",            //登录页面的地址【不拦截】"/**/*.html",            //html静态资源"/**/*.js",              //js静态资源"/**/*.css"              //css静态资源);}// 跨域，上面的拦截器配置了/*@Overridepublic void addCorsMappings(CorsRegistry registry) {}*/
}