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前言

有这样一个场景：
在一个springboot项目中，使用了 logback进行日志输出。但是项目中有部分功能使用了线程池，使用MDC进行日志ID的输出。

而默认的 LogbackMDCAdapter 无法传递参数到线程池中。因为它本身的实现是依赖于ThreadLocal进行数据传递的。

本文就将解决这个参数传递的问题，使用阿里巴巴开源的TransmittableThreadLocal 来重新实现一个MDCAdapter。

PS：有了解过 ThreadLocal 原理 以及 TTL 的朋友肯定知道，TTL 可以进行线程池级别的参数传递。这里不做过多描述。

正文

一、实现原理

为了实现在线程池中，可以传递 logid ，我们需要做两个操作：

1. 自定义MDCAdapter，使用 TTL 替换原先的 ThreadLocal；
2. 在自己项目中，创建 “同包同名” 的org.slf4j.impl.StaticMDCBinder，并指定 MDCAdapter 是自己自定义的实现；

二、项目环境

• Java版本：Java 1.8
• SpringBoot版本： 2.7.18
• TTL 版本：2.14.2

三、项目代码

3.1 pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>pine-mdc-ttl</artifactId><version>1.0-SNAPSHOT</version><packaging>jar</packaging><name>pine-mdc-ttl</name><url>http://maven.apache.org</url><properties><java.version>1.8</java.version><java.compiler.source>${java.version}</java.compiler.source><java.compiler.target>${java.version}</java.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><spring-boot.version>2.7.18</spring-boot.version><ttl.version>2.14.2</ttl.version><lombok.version>1.18.34</lombok.version></properties><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>com.alibaba</groupId><artifactId>transmittable-thread-local</artifactId></dependency><!--日志颜色--><dependency><groupId>org.fusesource.jansi</groupId><artifactId>jansi</artifactId><version>2.4.0</version></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.8</source><target>1.8</target><encoding>UTF-8</encoding></configuration></plugin><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><version>${spring-boot.version}</version><configuration><mainClass>org.BootDemoApplication</mainClass><skip>true</skip></configuration><executions><execution><id>repackage</id><goals><goal>repackage</goal></goals></execution></executions></plugin></plugins></build><dependencyManagement><dependencies><dependency><groupId>com.alibaba</groupId><artifactId>transmittable-thread-local</artifactId><version>${ttl.version}</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>${spring-boot.version}</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><version>${spring-boot.version}</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>${lombok.version}</version><scope>provided</scope><optional>true</optional></dependency></dependencies></dependencyManagement>
</project>

3.2 TtlMDCAdapter

package org.pine.mdcttl;import com.alibaba.ttl.TransmittableThreadLocal;
import org.slf4j.spi.MDCAdapter;import java.util.Deque;
import java.util.HashMap;
import java.util.Map;/*** 自定义MDC适配器：与TransmittableThreadLocal结合使用*/
public class TtlMDCAdapter implements MDCAdapter {private final ThreadLocalMapOfStacks threadLocalMapOfDeques = new ThreadLocalMapOfStacks();private final ThreadLocal<Map<String, String>> context = new TransmittableThreadLocal<Map<String, String>>() {@Overrideprotected Map<String, String> initialValue() {return new HashMap<>();}@Overridepublic Map<String, String> copy(Map<String, String> parentValue) {return parentValue != null ? new HashMap<>(parentValue) : null;}};@Overridepublic void put(String key, String val) {context.get().put(key, val);}@Overridepublic String get(String key) {return context.get().get(key);}@Overridepublic void remove(String key) {context.get().remove(key);}@Overridepublic void clear() {context.get().clear();context.remove();}@Overridepublic Map<String, String> getCopyOfContextMap() {return new HashMap<>(context.get());}@Overridepublic void setContextMap(Map<String, String> contextMap) {context.set(new HashMap<>(contextMap));}public void pushByKey(String key, String value) {this.threadLocalMapOfDeques.pushByKey(key, value);}public String popByKey(String key) {return this.threadLocalMapOfDeques.popByKey(key);}public Deque<String> getCopyOfDequeByKey(String key) {return this.threadLocalMapOfDeques.getCopyOfDequeByKey(key);}public void clearDequeByKey(String key) {this.threadLocalMapOfDeques.clearDequeByKey(key);}
}

3.3 ThreadLocalMapOfStacks

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package org.pine.mdcttl;import com.alibaba.ttl.TransmittableThreadLocal;import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;public class ThreadLocalMapOfStacks {final ThreadLocal<Map<String, Deque<String>>> tlMapOfStacks = new TransmittableThreadLocal<>();public ThreadLocalMapOfStacks() {}public void pushByKey(String key, String value) {if (key != null) {Map<String, Deque<String>> map = (Map)this.tlMapOfStacks.get();if (map == null) {map = new HashMap();this.tlMapOfStacks.set(map);}Deque<String> deque = (Deque)((Map)map).get(key);if (deque == null) {deque = new ArrayDeque();}((Deque)deque).push(value);((Map)map).put(key, deque);}}public String popByKey(String key) {if (key == null) {return null;} else {Map<String, Deque<String>> map = (Map)this.tlMapOfStacks.get();if (map == null) {return null;} else {Deque<String> deque = (Deque)map.get(key);return deque == null ? null : (String)deque.pop();}}}public Deque<String> getCopyOfDequeByKey(String key) {if (key == null) {return null;} else {Map<String, Deque<String>> map = (Map)this.tlMapOfStacks.get();if (map == null) {return null;} else {Deque<String> deque = (Deque)map.get(key);return deque == null ? null : new ArrayDeque(deque);}}}public void clearDequeByKey(String key) {if (key != null) {Map<String, Deque<String>> map = (Map)this.tlMapOfStacks.get();if (map != null) {Deque<String> deque = (Deque)map.get(key);if (deque != null) {deque.clear();}}}}
}

3.4 StaticMDCBinder

package org.slf4j.impl;import org.pine.mdcttl.TtlMDCAdapter;
import org.slf4j.spi.MDCAdapter;/*** 自定义MDC绑定器实现：* 1. 绑定自定义的ttl-MDC适配器* 2. 覆盖原先的org.slf4j.impl.StaticMDCBinder,使自定义的ttl-mdc适配器生效*/
public class StaticMDCBinder {public static final StaticMDCBinder SINGLETON = new StaticMDCBinder();public MDCAdapter getMDCA() {return new TtlMDCAdapter();}public String getMDCAdapterClassStr() {return TtlMDCAdapter.class.getName();}
}

3.5 启动类& 线程池配置

package org.pine;import com.alibaba.ttl.threadpool.TtlExecutors;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;import java.util.concurrent.ExecutorService;@SpringBootApplication
public class BootDemoApplication {public static void main(String[] args) {SpringApplication.run(BootDemoApplication.class, args);}@Bean(name = "ttlExecutorService")public ExecutorService ttlExecutorService() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(10);executor.setMaxPoolSize(100);executor.initialize();// 关键步骤：用TTL包装线程池return TtlExecutors.getTtlExecutorService(executor.getThreadPoolExecutor());}
}

3.6 logback-spring.xml

<?xml version="1.0" encoding="UTF-8" ?>
<configuration debug="false"><!-- 启用ANSI颜色支持（需要Jansi库） --><conversionRule conversionWord="clr" converterClass="org.springframework.boot.logging.logback.ColorConverter"/><conversionRule conversionWord="wex" converterClass="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter"/><appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"><encoder><!-- 带颜色的日志格式 --><!-- 格式化输出： %d表示日期， %thread表示线程名， %-5level: 级别从左显示5个字符宽度 %msg:日志消息, %n是换行符 %logger{0}：表示类名不进行任何缩写，输出完整的类名，%logger{50}：表示类名的最大长度为50个字符，超过的部分会被截断。--><!-- %clr(...){color}是Spring Boot对Logback的扩展，用于输出带颜色的日志。 颜色名称支持：black, red, green, yellow, blue, magenta, cyan, white等--><pattern>[%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){green}] %clr([%thread]){faint} %clr([logid=%X{logid:-system}]){red} %highlight(%-5level) %cyan(%logger{50}) - %msg%n</pattern></encoder></appender><!-- 日志输出级别 --><root level="INFO"><appender-ref ref="STDOUT"/></root>
</configuration>

四、测试

4.1 TestController

package org.pine.testcontroller;import lombok.extern.slf4j.Slf4j;
import org.slf4j.MDC;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import java.util.UUID;
import java.util.concurrent.ExecutorService;@RestController
@Slf4j
@RequestMapping("/test")
public class TestController {@Resource(name = "ttlExecutorService")private ExecutorService executorService;@RequestMapping("/test1")public String test() {String logId = UUID.randomUUID().toString();MDC.put("logid",logId );log.info("logId:{}", logId);executorService.submit(() -> {log.info("executorService-logId:{}", MDC.get("logid"));});return "test";}
}

4.2 调拥接口，观察日志

访问：http://localhost:8080/test/test1

观察到的日志结果：

[2025-03-14 14:54:10.304] [http-nio-8080-exec-1] [logid=a5610ff9-f250-4c3f-81f5-15c36d1a6278] INFO  org.pine.testcontroller.TestController - logId:a5610ff9-f250-4c3f-81f5-15c36d1a6278
[2025-03-14 14:54:10.317] [ThreadPoolTaskExecutor-1] [logid=a5610ff9-f250-4c3f-81f5-15c36d1a6278] INFO  org.pine.testcontroller.TestController - executorService-logId:a5610ff9-f250-4c3f-81f5-15c36d1a6278

可以看到线程池中输出的结果中，拼接了与其主线程相同的logid。这也是本文需要实现的效果。