一、为什么会有MDC(MappedDiagnosticContext)?
审计和调试分布式应用是logback的设计目标之一，在多线程环境中，不同的线程会处理不同的客户端，为了区分不同客户端日志输出，一种轻量级但不可取的做法是为每个实例化一个新的、完全分离日志记录器，这种方法会产生很多的日志记录器而且难以管理。
更轻量级的做法是唯一标记每个来自客户端的日志请求，为了唯一标记每个请求，用户把上下文信息放置到MDC中，MDC类的核心方法如下，完整方法参考MDC javadocs。
package org.slf4j; public class MDC { //Put a context value as identified by key //into the current thread's context map. public static void put(String key, String val); //Get the context identified by the key parameter. public static String get(String key); //Remove the context identified by the key parameter. public static void remove(String key); //Clear all entries in the MDC. public static void clear(); }
1、基本MDC的使用
package chapters.mdc; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.slf4j.MDC; import ch.qos.logback.classic.PatternLayout; import ch.qos.logback.core.ConsoleAppender; public class SimpleMDC { static public void main(String[] args) throws Exception { // You can put values in the MDC at any time. Before anything else // we put the first name MDC.put("first", "Dorothy"); Logger logger = LoggerFactory.getLogger(SimpleMDC.class); // We now put the last name MDC.put("last", "Parker"); // The most beautiful two words in the English language according // to Dorothy Parker: logger.info("Check enclosed."); logger.debug("The most beautiful two words in English."); MDC.put("first", "Richard"); MDC.put("last", "Nixon"); logger.info("I am not a crook."); logger.info("Attributed to the former US president. 17 Nov 1973."); } }
logback配置文件如下：
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender"> <layout> <Pattern>%X{first} %X{last} - %m%n</Pattern> </layout> </appender>
日志输出如下：
Dorothy Parker - Check enclosed. Dorothy Parker - The most beautiful two words in English. Richard Nixon - I am not a crook. Richard Nixon - Attributed to the former US president. 17 Nov 1973.
