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。
