MDC-链路追踪

1. 不引入MDC的日志打印

public class MDCTestController {

    private static final Logger logger = LoggerFactory.getLogger(MDCTestController.class);

    private static final String TRACE_Id = "traceId";

    public static void main(String[] args) {
        MDC.put(TRACE_Id, UUID.randomUUID().toString());
        logger.info("开始调用服务，进行业务处理");
        logger.info("业务处理完毕，可以释放空间了，避免内存泄露");
        MDC.remove(TRACE_Id);
        logger.info("traceId 还存在吗？{}", MDC.get(TRACE_Id) != null);
    }
}

2. 引入MDC的简单例子

public class MDCTestController {

    private static final Logger logger = LoggerFactory.getLogger(MDCTestController.class);

    private static final String TRACE_Id = "traceId";

    public static void main(String[] args) {
        MDC.put(TRACE_Id, UUID.randomUUID().toString());
        logger.info("开始调用服务，进行业务处理");
        logger.info("业务处理完毕，可以释放空间了，避免内存泄露");
        MDC.remove(TRACE_Id);
        logger.info("traceId 还存在吗？{}", MDC.get(TRACE_Id) != null);
    }
}

logback.xml

<configuration>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>[%t] [%X{traceId}] - %m%nPattern>
        layout>
    appender>
    <root level="debug">
        <appender-ref ref="CONSOLE"/>
    root>
configuration>

3. 使用AOP进行日志打印

1. logback.xml

<configuration>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>[%t] [%X{traceId}] - %m%nPattern>
        layout>
    appender>
    <root level="debug">
        <appender-ref ref="CONSOLE"/>
    root>
configuration>

2. 自定义注解（用于切入点）

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MDCInterface {
}

3. 切面类

@Aspect
@Component
@Slf4j
public class MDCAspect {

    private static final String TRACE_ID = "traceId";

    /**
     * 切入点
     */
    @Pointcut("@annotation(com.example.tooldemo.aspect.MDCInterface)")
    public void mdcPointCut(){}

    @Around("mdcPointCut()")
    public void process(ProceedingJoinPoint joinPoint){
        /**
         * 解析Log注解
         */
        try {
            MDC.put(TRACE_ID, UUID.randomUUID().toString());
            joinPoint.proceed();
        } catch (Throwable e) {
            log.error("MDC标识添加异常 ", e);
            throw new RuntimeException("MDC标识添加异常");
        } finally {
            MDC.clear();
        }
    }
}

4. 在需要追踪的方法上添加注解

@Api(tags = "MDC测试")
@RestController
@Slf4j
public class MDCTestController {

    @Autowired
    MDCService mdcService;

    @ApiOperation(value="MDC-traceId测试")
    @GetMapping("/testMdc")
    @MDCInterface  //添加注解
    public void testMdc(){
        log.info("MDC测试——Controller开始执行");
        mdcService.mdcTest();
        log.info("MDC测试——Controller执行结束");
    }
}

public interface MDCService {

    void mdcTest();

}

@Slf4j
@Service
public class MDCServiceImpl implements MDCService {

    @Override
    public void mdcTest() {
        log.info("MDC测试——service");
    }
}

MDC相关API

• clear(): 移除所有MDC
• get (String key) : 获取当前线程MDC中指定key的值
• getContext() : 获取当前线程MDC的MDC
• put(String key, Object o) : 往当前线程的MDC中存入指定的键值对
• remove(String key) : 删除当前线程MDC中指定的键值对