MDC的使用（Mapped Diagnostic Context）的使用

通常我們可能會有大量的任務需要提交提交到線程池執行，但是此時如果不對日志添加唯一標識進行區分的話回到錯亂一坨無法進行查看。因此可以對每一天日志添加唯一的標識，例如使用userid作為日志的唯一標志。這樣就可以使用MDC實現，MDC其實就是共享線程上下文。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;

import java.util.Map;
import java.util.concurrent.*;

import static java.util.concurrent.TimeUnit.SECONDS;


public class LogMDC {


    private static final Logger logger = LoggerFactory.getLogger("logic"); // 使用logic打印線程池執行任務的日志

    public static void main(String[] args) {
        MDC.put("sessionId", "sessionId_Value");
        MDC.put("userName", "userName_Value");

        ExecutorService executors = Executors.newFixedThreadPool(4);
        Future<Integer> f = executors.submit(new TaskMDC());


        try {
            System.out.println(f.get(2, SECONDS));
        } catch (InterruptedException e) {
            e.printStackTrace();
            logger.error(e.getMessage());
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (TimeoutException e) {
            e.printStackTrace();
        }

        // You can put values in the MDC at any time. Before anything else
        // we put the first name
        MDC.put("first", "Dorothy");


        // 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.");

    }

    static class TaskMDC implements Callable<Integer> {

        private Map<String, String> map;

        public TaskMDC() {
            this.map = MDC.getCopyOfContextMap();
        }

        @Override
        public Integer call() throws Exception {
            if (map != null) {
                MDC.setContextMap(map);
            }


            // The most beautiful two words in the English language according
            // to Dorothy Parker:
            logger.info("Call Thread Check enclosed.");
            logger.debug("Call Thread  The most beautiful two words in English.");

            MDC.put("first", "Richard");
            MDC.put("last", "Nixon");
            logger.info("Call Thread  I am not a crook.");
            logger.info("Call Thread   Attributed to the former US president. 17 Nov 1973.");
            return 2;
        }
    }
}

　　

log4j.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration>
    <appender name="console" class="org.apache.log4j.ConsoleAppender">
        <param name="target" value="System.out"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%-d{yyyy-MM-dd HH:mm:ss.SSS}  - %X{userName} - %m%n"/>
        </layout>
    </appender>
    <appender name="error" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="File" value="./logs/error.log"/>
        <param name="DatePattern" value="'.'yyyy-MM-dd"/>
        <param name="threshold" value="error"/>
        <param name="append" value="true"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="[%d{yyyy-MM-dd HH:mm:ss.SSS}]  - %X{userName} - %m%n"/>
        </layout>
    </appender>
    <appender name="logic" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="File" value="./logs/logic.log"/>
        <param name="DatePattern" value="'.'yyyy-MM-dd"/>
        <param name="threshold" value="info"/>
        <param name="append" value="true"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="[%d{yyyy-MM-dd HH:mm:ss.SSS}]  - %X{userName}  - %m%n"/>
        </layout>
    </appender>
    <appender name="trace" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="File" value="./logs/trace.log"/>
        <param name="DatePattern" value="'.'yyyy-MM-dd"/>
        <param name="threshold" value="info"/>
        <param name="append" value="true"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern"
                   value="[%d{yyyy-MM-dd HH:mm:ss.SSS}]  - %X{userName} - %m%n"/>
        </layout>
    </appender>
    <logger name="traceLog" additivity="false">
        <level value="info"/>
        <appender-ref ref="trace"/>
    </logger>
    <root>
        <level value="info"/>
        <appender-ref ref="console"/>
        <appender-ref ref="logic"/>
        <appender-ref ref="error"/>
    </root>
</log4j:configuration>

　　

 

pom：

       <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.21</version>
        </dependency>