使用Spring MVC或Spring Boot中打印或記錄日志一般使用AOP記錄Request請求和Response響應參數，在不使用AOP的前提下，如果在Filter中打印日志，在打印或消費請求類型為Content-Type:application/json的請求時，會出現嚴重的問題。

在Spring體系中，過濾器的定義我們一般采用繼承OncePerRequestFilter的方式，當然也可以使用原始的Filter。

錯誤寫法一：

如果不對request和response進行處理，使用偽代碼采用如下寫法打印請求和響應參數（注：此時request請求類型為Post，接收的是Json數據）

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

運行測試后你會發現拋出如下異常：

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]

錯誤寫法二：

如果不對request和response進行處理，使用偽代碼采用如下寫法打印請求和響應參數（注：此時request請求類型為Post，接收的是Json數據）

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

運行測試后你會發現拋出如下異常：

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

遇到這樣的問題你是不是有坐立不安、心煩意亂、百爪撓心的痛楚，不要著急，下面我給出一個解決方案。

首先我們使用裝飾器模式，創建request和response兩個包裝類，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: 請求包裝器* @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: 響應包裝器 * @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是一種寫入字符的一種操作類，可以寫入字符，TeePrintWriter繼承了他，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(); }}

接下來創建最重要的LoggingFilter類，繼承OncePerRequestFilter，或者直接繼承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@Configurationpublic class LoggingFilter extends OncePerRequestFilter { private static final String REQUEST_PREFIX_NAME = 'Request請求: '; private static final String RESPONSE_PREFIX_NAME = 'Response請求: '; @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()); } }

參考以上我整理出的代碼，你就會發現奇跡?。。?/p>

為什么要這么寫呢，其本質是把請求流拷貝了一份，一個供filterChain向下傳遞，一個來做流的消費，再有一個就是運用裝飾器模式的精髓所在。

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