最近有一个需要从拦截器中获取post请求的参数的需求，这里记录一下处理过程中出现的问题。
首先想到的就是request.getParameter(String )方法，但是这个方法只能在get请求中取到参数，post是不行的，后来想到了使用流的方式，调用request.getInputStream()获取流，然后从流中读取参数，如下代码所示：
String body = ""; StringBuilder stringBuilder = new StringBuilder(); BufferedReader bufferedReader = null; InputStream inputStream = null; try { inputStream = request.getInputStream(); if (inputStream != null) { bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); char[] charBuffer = new char[128]; int bytesRead = -1; while ((bytesRead = bufferedReader.read(charBuffer)) > 0) { stringBuilder.append(charBuffer, 0, bytesRead); } } else { stringBuilder.append(""); } } catch (IOException ex) { e.printStackTrace(); } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } } body = stringBuilder.toString();
代码中的body就是request中的参数，我这里传的是JSON数据：{"page": 1, "pageSize": 10}，那么body就是：body = "{"page": 1, "pageSize": 10}"，一个JSON字符串。这样是可以成功获取到post请求的body，但是，经过拦截器后，参数经过@RequestBody注解赋值给controller中的方法的时候，却抛出了一个这样的异常：
org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing
在网上查找资料后发现，request的输入流只能读取一次，那么这是为什么呢？下面是答案：
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()。
那么有什么办法可以用户解决呢？上面这篇博客中提到了解决方案，就是重写HttpServletRequestWrapper把request保存下来，然后通过过滤器把保存下来的request再填充进去，这样就可以多次读取request了。步骤如下所示：
①写一个类，继承HttpServletRequestWrapper
import javax.servlet.ReadListener; import javax.servlet.ServletInputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import java.io.*; public class RequestWrapper extends HttpServletRequestWrapper { private final String body; public RequestWrapper(HttpServletRequest request) { super(request); StringBuilder stringBuilder = new StringBuilder(); BufferedReader bufferedReader = null; InputStream inputStream = null; try { inputStream = request.getInputStream(); if (inputStream != null) { bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); char[] charBuffer = new char[128]; int bytesRead = -1; while ((bytesRead = bufferedReader.read(charBuffer)) > 0) { stringBuilder.append(charBuffer, 0, bytesRead); } } else { stringBuilder.append(""); } } catch (IOException ex) { } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } } body = stringBuilder.toString(); } @Override public ServletInputStream getInputStream() throws IOException { final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes()); ServletInputStream servletInputStream = new ServletInputStream() { @Override public boolean isFinished() { return false; } @Override public boolean isReady() { return false; } @Override public void setReadListener(ReadListener readListener) { } @Override public int read() throws IOException { return byteArrayInputStream.read(); } }; return servletInputStream; } @Override public BufferedReader getReader() throws IOException { return new BufferedReader(new InputStreamReader(this.getInputStream())); } public String getBody() { return this.body; } }
②拦截器层面
import com.alibaba.fastjson.JSON; import com.miniprogram.api.douyin.user.req.DyuserReq; import com.miniprogram.common.auth.VisitLimitCount; import com.miniprogram.common.cache.RedisCache; import com.miniprogram.common.config.InterceptorConfigMap; import com.miniprogram.common.config.InterceptorUrlConfig; import com.miniprogram.common.douyin.SearchEngineMapConstants; import com.miniprogram.common.response.Response; import com.miniprogram.common.session.*; import com.miniprogram.common.utils.DateUtil; import com.miniprogram.dao.common.UserLoginEntity.Users; import com.miniprogram.service.douyin.users.UsersService; import com.miniprogram.web.douyin.config.RequestWrapper; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.BeanUtils; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.handler.HandlerInterceptorAdapter; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.BufferedReader; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; @Component("authSecurityInterceptor") public class AuthSecurityInterceptor extends HandlerInterceptorAdapter { private Logger logger = LoggerFactory.getLogger(AuthSecurityInterceptor.class); @Autowired private RedisCache redisCache; @Autowired private VisitLimitCount visitLimitCount; @Override public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception { try { RequestWrapper requestWrapper = new RequestWrapper(httpServletRequest); String body = requestWrapper.getBody(); System.out.println(body); return true; }catch (Exception e){ logger.error("权限判断出错",e); } return false; } @Override public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception { } @Override public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception { } }
③过滤器Filter，用来把request传递下去
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 { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { ServletRequest requestWrapper = null; if(servletRequest instanceof HttpServletRequest) { requestWrapper = new RequestWrapper((HttpServletRequest) servletRequest); } if(requestWrapper == null) { filterChain.doFilter(servletRequest, servletResponse); } else { filterChain.doFilter(requestWrapper, servletResponse); } } @Override public void destroy() { } }
④在启动类中注册拦截器
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.web.servlet.MultipartConfigFactory; import org.springframework.boot.web.servlet.ServletComponentScan; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; @SpringBootApplication // @ServletComponentScan //注册过滤器注解 @Configuration public class WebApplication { public static void main(String[] args) { SpringApplication.run(WebApplication.class, args); } }
经测试，问题解决