详解在Spring MVC或Spring Boot中使用Filter打印请求参数问题

使用Spring MVC或Spring Boot中打印或记录日志一般使用AOP记录Request请求和Response响应参数，在不使用AOP的前提下，如果在Filter中打印日志，在打印或消费请求类型为Content-Type:application/json的请求时，会出现严重的问题。

在Spring体系中，过滤器的定义我们一般采用继承OncePerRequestFilter的方式，当然也可以使用原始的Filter。

错误写法一：

如果不对request和response进行处理，使用伪代码采用如下写法打印请求和响应参数（注：此时request请求类型为Post，接收的是Json数据）

  @Override
  protected void doFilterInternal(HttpServletRequest request, HttpServletResponse       
         response, FilterChain filterChain) throws ServletException, IOException {
    filterChain.doFilter(request, response);
    printRequestLog(request);
    printResonseLog(response);
  }

运行测试后你会发现抛出如下异常： 

java.io.IOException: Stream closed
 at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:359) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:132) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
 at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284) ~[na:1.8.0_191]
 at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326) ~[na:1.8.0_191]
 at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178) ~[na:1.8.0_191]
 at java.io.InputStreamReader.read(InputStreamReader.java:184) ~[na:1.8.0_191]
 at java.io.BufferedReader.fill(BufferedReader.java:161) ~[na:1.8.0_191]
 at java.io.BufferedReader.readLine(BufferedReader.java:324) ~[na:1.8.0_191]
 at java.io.BufferedReader.readLine(BufferedReader.java:389) ~[na:1.8.0_191]
 at com.micro.backend.filter.LoggingFilter.getBodyString(LoggingFilter.java:60) [classes/:na]
 at com.micro.backend.filter.LoggingFilter.doFilterInternal(LoggingFilter.java:49) [classes/:na]
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.1.14.RELEASE.jar:5.1.14.RELEASE]
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1639) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_191]
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_191]
 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.31.jar:9.0.31]
 at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]

错误写法二：

如果不对request和response进行处理，使用伪代码采用如下写法打印请求和响应参数（注：此时request请求类型为Post，接收的是Json数据）

  @Override
  protected void doFilterInternal(HttpServletRequest request, HttpServletResponse 
       response, FilterChain filterChain) throws ServletException, IOException {
    printRequestLog(request);
    printResonseLog(response);
    filterChain.doFilter(request, response);
  }

运行测试后你会发现抛出如下异常：  

org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing

遇到这样的问题你是不是有坐立不安、心烦意乱、百爪挠心的痛楚，不要着急，下面我给出一个解决方案。

首先我们使用装饰器模式，创建request和response两个包装类，如下：

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;
import java.nio.charset.Charset;
/**
* @Description:  请求包装器
* @Author:     liuliya
* @CreateDate:   2020/4/29 10:00
*/
public class RequestWrapper extends HttpServletRequestWrapper {
  
  private final byte[] body;
 
  public RequestWrapper(HttpServletRequest request) throws IOException {
    super(request);
    body = getRequestBodyString(request).getBytes(Charset.defaultCharset());
  }
 
  @Override
  public BufferedReader getReader() throws IOException {
    return new BufferedReader(new InputStreamReader(getInputStream()));
  }
 
  @Override
  public ServletInputStream getInputStream() throws IOException {
 
    final ByteArrayInputStream bais = new ByteArrayInputStream(body);
 
    return new ServletInputStream() {
 
      @Override
      public int read() throws IOException {
        return bais.read();
      }
 
      @Override
      public boolean isFinished() {
        return false;
      }
 
      @Override
      public boolean isReady() {
        return false;
      }
 
      @Override
      public void setReadListener(ReadListener listener) {
 
      }
    };
  }
 
  public String getRequestBodyString(ServletRequest request) {
    StringBuilder sb = new StringBuilder();
    InputStream inputStream = null;
    BufferedReader reader = null;
    try {
      inputStream = request.getInputStream();
      reader = new BufferedReader(new InputStreamReader(inputStream, Charset.defaultCharset()));
      String line;
      while ((line = reader.readLine()) != null) {
        sb.append(line);
      }
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      if (inputStream != null) {
        try {
          inputStream.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (reader != null) {
        try {
          reader.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
    return sb.toString();
  }
}

package com.micro.backend.filter.support;
 
import org.apache.commons.io.output.TeeOutputStream; 
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
 
/**
 * @Description: 响应包装器
 * @Author: liuliya
 * @CreateDate: 2020/4/29 10:00
 */
public class ResponseWrapper extends HttpServletResponseWrapper {
 
  private final ByteArrayOutputStream bos = new ByteArrayOutputStream();
  private PrintWriter writer = new PrintWriter(bos);
 
  public ResponseWrapper(HttpServletResponse response) {
    super(response);
  }
 
  @Override
  public ServletResponse getResponse() {
    return this;
  }
 
  @Override
  public ServletOutputStream getOutputStream() throws IOException {
    return new ServletOutputStream() {
      @Override
      public boolean isReady() {
        return false;
      }
 
      @Override
      public void setWriteListener(WriteListener listener) {
 
      }
 
      private TeeOutputStream tee = new TeeOutputStream(ResponseWrapper.super.getOutputStream(), bos);
 
      @Override
      public void write(int b) throws IOException {
        tee.write(b);
      }
    };
  }
 
  @Override
  public PrintWriter getWriter() throws IOException {
    return new TeePrintWriter(super.getWriter(), writer);
  }
 
  public byte[] toByteArray() {
    return bos.toByteArray();
  }
}

package com.micro.backend.filter.support;
import java.io.PrintWriter;
//PrintWriter是一种写入字符的一种操作类，可以写入字符，TeePrintWriter继承了他，主要功能是把原始的字符流copy到branch里面。
public class TeePrintWriter extends PrintWriter {
 
  PrintWriter branch;
 
  public TeePrintWriter(PrintWriter main, PrintWriter branch) {
    super(main, true);
    this.branch = branch;
  }
 
  public void write(char buf[], int off, int len) {
    super.write(buf, off, len);
    super.flush();
    branch.write(buf, off, len);
    branch.flush();
  }
 
  public void write(String s, int off, int len) {
    super.write(s, off, len);
    super.flush();
    branch.write(s, off, len);
    branch.flush();
  }
 
  public void write(int c) {
    super.write(c);
    super.flush();
    branch.write(c);
    branch.flush();
  }
 
  public void flush() {
    super.flush();
    branch.flush();
  }
}

接下来创建最重要的LoggingFilter类，继承OncePerRequestFilter，或者直接继承Servlet中原始的Filter。

package com.micro.backend.filter;
 
import com.micro.backend.filter.support.RequestWrapper;
import com.micro.backend.filter.support.ResponseWrapper;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.OncePerRequestFilter;
 
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
 
/**
* @Author:     liuliya
* @CreateDate:   2020/4/28 23:30
*/
@Slf4j
@Configuration
public class LoggingFilter extends OncePerRequestFilter {
  
  private static final String REQUEST_PREFIX_NAME = "Request请求: ";
  private static final String RESPONSE_PREFIX_NAME = "Response请求: ";
 
  @Override
  protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
    request = new RequestWrapper(request);
    response = new ResponseWrapper(response);
    filterChain.doFilter(request, response);
    printRequestLog(request);
    printResponseLog((ResponseWrapper) response);
  }
 
  private void printRequestLog(final HttpServletRequest request) {
    StringBuilder msg = new StringBuilder();
    msg.append(REQUEST_PREFIX_NAME);
    HttpSession session = request.getSession(false);
    if (session != null) {
      msg.append("sessionId = ").append(session.getId()).append("; ");
    }
    if (request.getMethod() != null) {
      msg.append("method = ").append(request.getMethod()).append("; ");
    }
    if (request.getContentType() != null) {
      msg.append("contentType = ").append(request.getContentType()).append("; ");
    }
    msg.append("uri = ").append(request.getRequestURI());
    if (request.getQueryString() != null) {
      msg.append('?').append(request.getQueryString());
    }
 
    if (request instanceof RequestWrapper && !isMultipart(request) && !isBinaryContent(request)) {
      RequestWrapper requestWrapper = (RequestWrapper) request;
      msg.append("; payload = ").append(requestWrapper.getRequestBodyString(request));
    }
    log.info(msg.toString());
  }
 
  private boolean isBinaryContent(final HttpServletRequest request) {
    if (request.getContentType() == null) {
      return false;
    }
    return request.getContentType().startsWith("image")
        || request.getContentType().startsWith("video")
        || request.getContentType().startsWith("audio");
  }
 
  private boolean isMultipart(final HttpServletRequest request) {
    return request.getContentType() != null
        && request.getContentType().startsWith("multipart/form-data");
  }
 
  private void printResponseLog(final ResponseWrapper response) {
    StringBuilder msg = new StringBuilder();
    msg.append(RESPONSE_PREFIX_NAME);
    try {
      msg.append("; payload = ")
          .append(new String(response.toByteArray(), response.getCharacterEncoding()));
    } catch (UnsupportedEncodingException e) {
      log.warn("Failed to parse response payload", e);
    }
    log.info(msg.toString());
  } 
}

参考以上我整理出的代码，你就会发现奇迹！！！

为什么要这么写呢，其本质是把请求流拷贝了一份，一个供filterChain向下传递，一个来做流的消费，再有一个就是运用装饰器模式的精髓所在。

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