1.MDC
1.简介
MDC 介绍 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。MDC 可以看成是一个与当前线程绑定的Map，可以往其中添加键值对。MDC 中包含的内容可以被同一线程中执行的代码所访问。当前线程的子线程会继承其父线程中的 MDC 的内容。当需要记录日志时，只需要从 MDC 中获取所需的信息即可。MDC 的内容则由程序在适当的时候保存进去。对于一个 Web 应用来说，通常是在请求被处理的最开始保存这些数据。 简而言之，MDC就是日志框架提供的一个InheritableThreadLocal，项目代码中可以将键值对放入其中，然后使用指定方式取出打印即可。
原理：当请求来时生成一个traceId放在InheritableThreadLocal里，然后打印时去取就行了。但在不改动原有输出语句的前提下自然需要日志框架的支持了。
2.使用
2.1配置TraceId 过滤器
@Order(1)
@WebFilter(urlPatterns = "/*",filterName = "traceIdFilter")
public class TraceIdFilter implements Filter {
public final static String MDC_TRACE_ID = "traceId";
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest) request;
String traceId = httpRequest.getHeader(MDC_TRACE_ID);
if (StringUtils.isBlank(traceId)) {
traceId = IdUtil.fastSimpleUUID();;
}
MDC.put(MDC_TRACE_ID, traceId);
chain.doFilter(request, response);
}
}
2.2 启动类开启
@SpringBootApplication
@ServletComponentScan
public class OpenApp {
public static void main(String[] args) {
SpringApplication.run(OpenApp.class, args);
}
}
2.3 配置文件配置日志输出格式
# Spring Boot 日志配置
logging:
# 控制台日志输出格式
pattern:
console: "%d{yyyy-MM-dd HH:mm:ss.SSS} %clr(%-5level) %clr([%X{traceId}]) %clr(${PID:-}) --- %clr(%logger{50}) - %m%n"
# 注释说明：
# %d{yyyy-MM-dd HH:mm:ss.SSS}: 时间戳，格式为年-月-日 时:分:秒:毫秒
# %-5level: 日志级别，左对齐且至少占用5个字符宽度
# %clr(...): 使用颜色编码（如果支持）
# [%X{traceId}]: Mapped Diagnostic Context中的traceId，用于记录跟踪请求的唯一标识
# ${PID:-}: 当前进程ID，如果没有则显示空字符串
# ---: 分隔符
# %logger{50}: 日志器名称，最多显示50个字符
# %m: 日志消息内容
# %n: 换行符
三、结果显示
主线程已经得到了我们想要的结果：
创建一个子线程
子线程并没有得到我们想要的结果，那怎么解决呢？？？
四、TransmittableThreadLocal实现链路追踪
4.1引入依赖
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>transmittable-thread-local</artifactId>
<version>2.11.5</version>
<scope>compile</scope>
</dependency>4.2、重写{LogbackMDCAdapter}类
注意：要在org.slf4j包下写才可以。
package org.slf4j;
import ch.qos.logback.classic.util.LogbackMDCAdapter;
import org.slf4j.spi.MDCAdapter;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
/**
* 描述：
* 重写{@link LogbackMDCAdapter}类，搭配TransmittableThreadLocal实现父子线程之间的数据传递
* 内容直接从{@link LogbackMDCAdapter}类中copy。把copyOnThreadLocal实例化对象更改为TransmittableThreadLocal即可
*/
public class TtlMDCAdapter implements MDCAdapter {
final ThreadLocal<Map<String, String>> copyOnThreadLocal = new InheritableThreadLocal();
private static final int WRITE_OPERATION = 1;
private static final int MAP_COPY_OPERATION = 2;
final ThreadLocal<Integer> lastOperation = new ThreadLocal();
private static TtlMDCAdapter mtcMDCAdapter;
static {
mtcMDCAdapter = new TtlMDCAdapter();
MDC.mdcAdapter = mtcMDCAdapter;
}
public TtlMDCAdapter() {
}
public static MDCAdapter getInstance() {
return mtcMDCAdapter;
}
private Integer getAndSetLastOperation(int op) {
Integer lastOp = (Integer)this.lastOperation.get();
this.lastOperation.set(op);
return lastOp;
}
private boolean wasLastOpReadOrNull(Integer lastOp) {
return lastOp == null || lastOp == MAP_COPY_OPERATION;
}
private Map<String, String> duplicateAndInsertNewMap(Map<String, String> oldMap) {
Map<String, String> newMap = Collections.synchronizedMap(new HashMap());
if (oldMap != null) {
synchronized(oldMap) {
newMap.putAll(oldMap);
}
}
this.copyOnThreadLocal.set(newMap);
return newMap;
}
public void put(String key, String val) throws IllegalArgumentException {
if (key == null) {
throw new IllegalArgumentException("key cannot be null");
} else {
Map<String, String> oldMap = (Map)this.copyOnThreadLocal.get();
Integer lastOp = this.getAndSetLastOperation(WRITE_OPERATION);
if (!this.wasLastOpReadOrNull(lastOp) && oldMap != null) {
oldMap.put(key, val);
} else {
Map<String, String> newMap = this.duplicateAndInsertNewMap(oldMap);
newMap.put(key, val);
}
}
}
public void remove(String key) {
if (key != null) {
Map<String, String> oldMap = (Map)this.copyOnThreadLocal.get();
if (oldMap != null) {
Integer lastOp = this.getAndSetLastOperation(WRITE_OPERATION);
if (this.wasLastOpReadOrNull(lastOp)) {
Map<String, String> newMap = this.duplicateAndInsertNewMap(oldMap);
newMap.remove(key);
} else {
oldMap.remove(key);
}
}
}
}
public void clear() {
this.lastOperation.set(WRITE_OPERATION);
this.copyOnThreadLocal.remove();
}
public String get(String key) {
Map<String, String> map = (Map)this.copyOnThreadLocal.get();
return map != null && key != null ? (String)map.get(key) : null;
}
public Map<String, String> getPropertyMap() {
this.lastOperation.set(MAP_COPY_OPERATION);
return (Map)this.copyOnThreadLocal.get();
}
public Set<String> getKeys() {
Map<String, String> map = this.getPropertyMap();
return map != null ? map.keySet() : null;
}
public Map<String, String> getCopyOfContextMap() {
Map<String, String> hashMap = copyOnThreadLocal.get();
return hashMap == null ? null : new HashMap(hashMap);
}
public void setContextMap(Map<String, String> contextMap) {
this.lastOperation.set(WRITE_OPERATION);
Map<String, String> newMap = Collections.synchronizedMap(new HashMap());
newMap.putAll(contextMap);
this.copyOnThreadLocal.set(newMap);
}
}
4.3、更改spring.factories
在resource/META-INF/spring.factories中进行配置。
org.springframework.context.ApplicationContextInitializer=\
com.jarvan.demo.config.TtlMDCAdapterInitializer4.4、TtlMDCAdapterInitializer类如下
package com.by.config;
import org.slf4j.TtlMDCAdapter;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
public class TtlMDCAdapterInitializer implements ApplicationContextInitializer {
@Override
public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
TtlMDCAdapter.getInstance();
}
}4.5、结果展示
