Java记录日志的MDC全链路追踪方案

// 示例：在请求开始时设置MDC
public void onRequestStart(String traceId) {
    MDC.put("traceId", traceId); // 设置traceId
    // ... 业务逻辑 ...
    logger.info("处理请求...");
}

// 示例：在请求结束时清除MDC
public void onRequestEnd() {
    MDC.clear(); // 清除所有MDC内容，或者MDC.remove("traceId")
}

// 示例：Logback配置，在pattern中加入%X{traceId}
// <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - [traceId=%X{traceId}] %msg%n</pattern>

// Web请求拦截器示例
@Component
public class TraceIdInterceptor implements HandlerInterceptor {

    private static final String TRACE_ID_HEADER = "X-B3-TraceId"; // 常用请求头

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        String traceId = request.getHeader(TRACE_ID_HEADER);
        if (traceId == null || traceId.isEmpty()) {
            traceId = UUID.randomUUID().toString().replace("-", ""); // 生成新的Trace ID
        }
        MDC.put("traceId", traceId);
        // 如果需要，也可以把traceId放回response header，方便前端或下游服务获取
        response.setHeader(TRACE_ID_HEADER, traceId);
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        MDC.clear(); // 清理MDC，非常重要！
    }
}

// RestTemplate拦截器示例
@Component
public class RestTemplateTraceIdInterceptor implements ClientHttpRequestInterceptor {
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        String traceId = MDC.get("traceId");
        if (traceId != null) {
            request.getHeaders().add("X-B3-TraceId", traceId);
        }
        return execution.execute(request, body);
    }
}

// 配置RestTemplate
// @Bean
// public RestTemplate restTemplate(RestTemplateBuilder builder) {
//     return builder.additionalInterceptors(new RestTemplateTraceIdInterceptor()).build();
// }

// 异步任务MDC上下文传递示例
@Configuration
public class AsyncConfig implements AsyncConfigurer {

    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(10);
        executor.setMaxPoolSize(20);
        executor.setQueueCapacity(200);
        executor.setThreadNamePrefix("async-task-");
        executor.setTaskDecorator(new MDCTaskDecorator()); // 关键在这里
        executor.initialize();
        return executor;
    }

    // 自定义TaskDecorator
    static class MDCTaskDecorator implements TaskDecorator {
        @Override
        public Runnable decorate(Runnable runnable) {
            Map<String, String> contextMap = MDC.getCopyOfContextMap(); // 获取当前线程的MDC副本
            return () -> {
                if (contextMap != null) {
                    MDC.setContextMap(contextMap); // 在子线程中设置MDC
                }
                try {
                    runnable.run();
                } finally {
                    MDC.clear(); // 子线程执行完后也要清理
                }
            };
        }
    }
}