日志框架LOG4J2系列五——@Plugin插件实现不同线程打印日志

一、实战背景

在实际的业务开发中我们会遇到以下场景：我们为服务开启监控线程，然后按照业务性质可以将线程分为业务线程和监控线程，我们想要将业务线程的日子全部打印到业务日志中，而监控线程的日志全部打印到监控日志中。一种方法是我们根据log4j2日志进行配置，通过指定Logger的方式实现；本文将提供另一种实现方式，根据线程名称打印不同的日志文件。插件说明可以参考上一章日志框架LOG4J2系列四——log4j2的plugins(插件)使用

二、工程配置

• maven依赖

<properties>
    <log4j.version>2.14.1log4j.version>
properties>
<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4jgroupId>
        <artifactId>log4j-slf4j-implartifactId>
        <version>${log4j.version}version>
    dependency>
    <dependency>
        <groupId>org.apache.logging.log4jgroupId>
        <artifactId>log4j-coreartifactId>
        <version>${log4j.version}version>
    dependency>
dependencies>

这里需要使用@Plugin和StrLookup，log4j-slf4j-impl会引入log4j2-core，但是限定了scope是runtime，我们必须手动引入log4j2-core组件。

三、log4j2配置

首先我们先要拓展一个StrLookUp插件，使用@Plugin表明此时一个log4j2的插件，定义插件的名称和属性

package com.demo.log.plugins;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.lookup.StrLookup;

// 表明是一个log4j2的插件，且是拓展了StrLookup 的插件
@Plugin(name = "threadName", category = StrLookup.CATEGORY)
public class ThreadName implements StrLookup {
	// 插件的功能即根据key值获取相应结果，这里我们直接返回线程名字
    @Override
    public String lookup(String key) {
        return Thread.currentThread().getName();
    }

    @Override
    public String lookup(LogEvent event, String key) {
        return event.getThreadName() == null ? Thread.currentThread().getName()
                : event.getThreadName();
    }
}

使用Routing，根据插件lookup的结果即线程名称选择路由routes，routes下面每个route都是一个RollingFile，这样就能将线程打印到不同的地方

<Configuration name="log-demo-config" status="error" monitorInterval="10">
    <Appenders>
        
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="[%d{yyyy-MM-dd;HH:mm:ss.SSS Z}] [%-5p] [%t] [%c] %m%n">PatternLayout>
        Console>
        
        <Routing name="Routing">
            <Routes pattern="$${threadName:threadName}">
                <Route>
                    <RollingFile name="RollingFile-${threadName:threadName}"
                                 fileName="J:\JavaWorkSpace\SpringLearning\src\main\resources\log\thread\thread-${threadName:threadName}.log"
                                 filePattern="J:\JavaWorkSpace\SpringLearning\src\main\resources\log\thread\thread-${threadName:threadName}-%i.log">
                        <PatternLayout pattern="[%d{yyyy-MM-dd HH:mm:ss,SSS Z}] [%-5p] [%t] [%c %L] %m%n"/>
                        <Policies>
                            <SizeBasedTriggeringPolicy size="10 MB" />
                        Policies>
                        <DefaultRolloverStrategy max="10"/>
                    RollingFile>
                Route>
            Routes>
        Routing>
    Appenders>
    <Loggers>
        <Logger name="com.demo.log" level="INFO" additivity="false">
            <AppenderRef ref="Routing">AppenderRef>
        Logger>
    Loggers>
Configuration>

四、实验

package com.demo.log;

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

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class LogDemo {

    private static final Logger LOGGER = LoggerFactory.getLogger(LogDemo.class);

    private static ThreadPoolExecutor threadPoolExecutor;

    public static void main(String[] args) {
        threadPoolExecutor = new ThreadPoolExecutor(10, 20, 1, TimeUnit.MINUTES, new LinkedBlockingDeque<>());
        for (int i = 0; i < 10; i++) {
            int threadNum = i;
            threadPoolExecutor.execute(() -> {
                while (true) {
                    LOGGER.info("thread-" + threadNum);
                }
            });
        }
    }
}

运行logdemo查看效果，将在log\thread下面按线程保存不同日志文件：

[2021-09-22 22:42:30,174 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,241 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,274 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,274 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,275 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,275 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,276 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,289 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,289 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,290 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,290 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,290 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,292 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,293 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,293 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,293 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,301 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0
[2021-09-22 22:42:30,323 +0800] [INFO ] [pool-2-thread-1] [com.demo.log.LogDemo 22] thread-0