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网站查看空间商,如何自己设计创建一个网站,辽宁建设工程信息网审计报告,客户关系管理系统软件之前有一篇文章简单的介绍过MDC#xff0c;这次结合具体的案例、生产中的具体问题深入了解一下MDC。MDC介绍1、简介#xff1a;MDC#xff08;Mapped Diagnostic Context#xff0c;映射调试上下文#xff09;是 log4j 、logback及log4j2 提供的一种方便在多线程条件下记录…之前有一篇文章简单的介绍过MDC这次结合具体的案例、生产中的具体问题深入了解一下MDC。MDC介绍1、简介MDCMapped Diagnostic Context映射调试上下文是 log4j 、logback及log4j2 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哈希表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2、API说明clear()移除所有MDCget (String key)获取当前线程MDC中指定key的值getContext()获取当前线程MDC的MDCput(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3、优点代码简洁日志风格统一不需要在log打印中手动拼写traceId即LOGGER.info(traceId:{} , traceId)MDC使用1、添加拦截器public class LogInterceptor implements HandlerInterceptor { Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { //如果有上层调用就用上层的ID String traceId request.getHeader(Constants.TRACE_ID); if (traceId null) { traceId TraceIdUtil.getTraceId(); } MDC.put(Constants.TRACE_ID, traceId); return true; } Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { } Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { //调用结束后删除 MDC.remove(Constants.TRACE_ID); } }2、修改日志格式property namepattern[TRACEID:%X{traceId}] %d{HH:mm:ss.SSS} %-5level %class{-1}.%M()/%L - %msg%xEx%n/property重点是%X{traceId}traceId和MDC中的键名称一致简单使用就这么容易但是在有些情况下traceId将获取不到MDC 存在的问题子线程中打印日志丢失traceIdHTTP调用丢失traceId丢失traceId的情况来一个再解决一个绝不提前优化解决MDC存在的问题子线程日志打印丢失traceId子线程在打印日志的过程中traceId将丢失解决方式为重写线程池对于直接new创建线程的情况不考略【实际应用中应该避免这种用法】重写线程池无非是对任务进行一次封装线程池封装类ThreadPoolExecutorMdcWrapper.javapublic class ThreadPoolExecutorMdcWrapper extends ThreadPoolExecutor { public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueueRunnable workQueue) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue); } public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueueRunnable workQueue, ThreadFactory threadFactory) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory); } public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueueRunnable workQueue, RejectedExecutionHandler handler) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler); } public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueueRunnable workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) { super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler); } Override public void execute(Runnable task) { super.execute(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap())); } Override public T FutureT submit(Runnable task, T result) { return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()), result); } Override public T FutureT submit(CallableT task) { return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap())); } Override public Future? submit(Runnable task) { return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap())); } }说明继承ThreadPoolExecutor类重新执行任务的方法通过ThreadMdcUtil对任务进行一次包装线程traceId封装工具类ThreadMdcUtil.javapublic class ThreadMdcUtil { public static void setTraceIdIfAbsent() { if (MDC.get(Constants.TRACE_ID) null) { MDC.put(Constants.TRACE_ID, TraceIdUtil.getTraceId()); } } public static T CallableT wrap(final CallableT callable, final MapString, String context) { return () - { if (context null) { MDC.clear(); } else { MDC.setContextMap(context); } setTraceIdIfAbsent(); try { return callable.call(); } finally { MDC.clear(); } }; } public static Runnable wrap(final Runnable runnable, final MapString, String context) { return () - { if (context null) { MDC.clear(); } else { MDC.setContextMap(context); } setTraceIdIfAbsent(); try { runnable.run(); } finally { MDC.clear(); } }; } }说明【以封装Runnable为例】判断当前线程对应MDC的Map是否存在存在则设置设置MDC中的traceId值不存在则新生成针对不是子线程的情况如果是子线程MDC中traceId不为null执行run方法代码等同于以下写法会更直观public static Runnable wrap(final Runnable runnable, final MapString, String context) { return new Runnable() { Override public void run() { if (context null) { MDC.clear(); } else { MDC.setContextMap(context); } setTraceIdIfAbsent(); try { runnable.run(); } finally { MDC.clear(); } } }; }重新返回的是包装后的Runnable在该任务执行之前【runnable.run()】先将主线程的Map设置到当前线程中【 即MDC.setContextMap(context)】这样子线程和主线程MDC对应的Map就是一样的了判断当前线程对应MDC的Map是否存在存在则设置设置MDC中的traceId值不存在则新生成针对不是子线程的情况如果是子线程MDC中traceId不为null执行run方法HTTP调用丢失traceId在使用HTTP调用第三方服务接口时traceId将丢失需要对HTTP调用工具进行改造在发送时在request header中添加traceId在下层被调用方添加拦截器获取header中的traceId添加到MDC中HTTP调用有多种方式比较常见的有HttpClient、OKHttp、RestTemplate所以只给出这几种HTTP调用的解决方式1、HttpClient实现HttpClient拦截器public class HttpClientTraceIdInterceptor implements HttpRequestInterceptor { Override public void process(HttpRequest httpRequest, HttpContext httpContext) throws HttpException, IOException { String traceId MDC.get(Constants.TRACE_ID); //当前线程调用中有traceId则将该traceId进行透传 if (traceId ! null) { //添加请求体 httpRequest.addHeader(Constants.TRACE_ID, traceId); } } }实现HttpRequestInterceptor接口并重写process方法如果调用线程中含有traceId则需要将获取到的traceId通过request中的header向下透传下去为HttpClient添加拦截器private static CloseableHttpClient httpClient HttpClientBuilder.create() .addInterceptorFirst(new HttpClientTraceIdInterceptor()) .build();通过addInterceptorFirst方法为HttpClient添加拦截器2、OKHttp实现OKHttp拦截器public class OkHttpTraceIdInterceptor implements Interceptor { Override public Response intercept(Chain chain) throws IOException { String traceId MDC.get(Constants.TRACE_ID); Request request null; if (traceId ! null) { //添加请求体 request chain.request().newBuilder().addHeader(Constants.TRACE_ID, traceId).build(); } Response originResponse chain.proceed(request); return originResponse; } }实现Interceptor拦截器重写interceptor方法实现逻辑和HttpClient差不多如果能够获取到当前线程的traceId则向下透传为OkHttp添加拦截器private static OkHttpClient client new OkHttpClient.Builder() .addNetworkInterceptor(new OkHttpTraceIdInterceptor()) .build();调用addNetworkInterceptor方法添加拦截器3、RestTemplate实现RestTemplate拦截器public class RestTemplateTraceIdInterceptor implements ClientHttpRequestInterceptor { Override public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException { String traceId MDC.get(Constants.TRACE_ID); if (traceId ! null) { httpRequest.getHeaders().add(Constants.TRACE_ID, traceId); } return clientHttpRequestExecution.execute(httpRequest, bytes); } }实现ClientHttpRequestInterceptor接口并重写intercept方法其余逻辑都是一样的不重复说明为RestTemplate添加拦截器restTemplate.setInterceptors(Arrays.asList(new RestTemplateTraceIdInterceptor()));调用setInterceptors方法添加拦截器4、第三方服务拦截器HTTP调用第三方服务接口全流程traceId需要第三方服务配合第三方服务需要添加拦截器拿到request header中的traceId并添加到MDC中public class LogInterceptor implements HandlerInterceptor { Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { //如果有上层调用就用上层的ID String traceId request.getHeader(Constants.TRACE_ID); if (traceId null) { traceId TraceIdUtils.getTraceId(); } MDC.put(traceId, traceId); return true; } Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { } Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { MDC.remove(Constants.TRACE_ID); } }说明先从request header中获取traceId从request header中获取不到traceId则说明不是第三方调用直接生成一个新的traceId将生成的traceId存入MDC中除了需要添加拦截器之外还需要在日志格式中添加traceId的打印如下property namepattern[TRACEID:%X{traceId}] %d{HH:mm:ss.SSS} %-5level %class{-1}.%M()/%L - %msg%xEx%n/property“注意需要添加%X{traceId}”最后说一句别白嫖求关注如果这篇文章对你有所帮助或者有所启发的话帮忙点赞、在看、转发、收藏你的支持就是我坚持下去的最大动力