过滤器+slf4j(MDC)实现日志记录请求ID

过滤器

从请求取requestid若没有则生成，随后放入MDC上下文中

MDC（Mapped Diagnostic Context，映射调试上下文）是 log4j 和 logback 提供的一种方便在多线程条件下记录日志的功能。

确保了多进程下进程之间在MDC存放的值是没有相互的影响的

MDC的介绍

---

package com.jerry.log;
import org.slf4j.MDC;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.UUID;


/* * 在日志上下文增加参数，在日志中可以打印该参数，如RequestId，则日志配置：%d{yyyy-MM-dd HH:mm:ss.SSS} [%X{RequestId}] [%thread] %-5level %logger{36} - %msg%n
 * 则 RequestId 会打印在中括号里，%X{参数名}  是格式
 **/

@Component
public class MDCFilter implements Filter {
    /**
     * 设置响应头，响应头名字（惯例是大写）
     */
    private static final String REQUEST_ID_HEADER = "RequestId";
    /**
     * 设置到 MDC 里的key（惯例使用小驼峰，为了统一这里也用大写）
     */
    private static final String REQUEST_ID = "RequestId";

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;

        String requestId = httpRequest.getHeader(REQUEST_ID_HEADER);
        if (requestId == null) {
            requestId = UUID.randomUUID().toString();
        }

        // 还有更加准确的方法
        String ip = getRequestSourceIp(httpRequest);

        MDC.put(REQUEST_ID, requestId);
        MDC.put("IP", ip);
        httpResponse.setHeader(REQUEST_ID_HEADER, requestId);

        try {
            chain.doFilter(request, response);
        } finally {
            MDC.clear();
        }
    }

    @Override
    public void destroy() {
    }


    /**
     * 获取请求来源的IP,可以适应前置部署有Nginx等反向代理软件等的情况. HTTP_CLIENT_IP 无法伪造，所以放在第一个
     *
     * @param request
     * @return
     */
    public static String getRequestSourceIp(HttpServletRequest request) {
        String ip = request.getHeader("HTTP_CLIENT_IP");

        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_X_FORWARDED_FOR");
        }

        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_X_FORWARDED");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_FORWARDED");
        }

        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("X-FORWARDED-FOR");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("WL-Proxy-Client-IP");
        }

        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getRemoteAddr();
        }
        return ip;
    }
}

配置过滤器（web.xml）

<filter>
    <filter-name>MDCFilter</filter-name>
    <filter-class>com.jerry.log.MDCFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>MDCFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

日志文件配置（log4j,properties）

log4j.rootLogger = debug,stdout,E,I,C
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}|[%X{RequestId}][ %t:%r ] %m%n

此处可以取到之前mdc上下文中的参数

requestid和线程id

log4j.properties 详解与配置步骤