Java SLF4J

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Introduction

Simple Logging Facade for Java (SLF4J)

The Simple Logging Facade for Java (SLF4J) serves as a simple facade or abstraction for various logging frameworks (e.g. java.util.logging, logback, log4j) allowing the end user to plug in the desired logging framework at deployment time.

Configuation

pom.xml

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<properties>
    <sl4j.version>2.11.1</sl4j.version>
</properties>

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>${sl4j.version}</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>${sl4j.version}</version>
</dependency>

log4j2.xml

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<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="ERROR">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
    </Appenders>
    <Loggers>
        <Logger name="com.anda.engine" level="DEBUG" additivity="false">
            <AppenderRef ref="Console"/>
        </Logger>
        <Root level="WARM">
            <AppenderRef ref="Console"/>
        </Root>
    </Loggers>
</Configuration>

注：如果不添加additivity=”false”属性，输出重复log

Enable AsyncLogger

  1. JVM启动参数（boot.ini）加上“-DLog4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector”

  2. classpath中添加文件“log4j2.component.properties”，文件增加以下内容：“Log4jContextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector”

  3. 手工指定部分Logger采用异步方式log4j2.xml配置文件中使用AsyncRoot/AsyncLogger替代Root/Logger

Usage

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val logger = LogManager.getLogger()
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-Dlog4j.configurationFile=log4j2-dev.xml

Reference

https://www.slf4j.org/manual.html