近期，碰到需要将项目中的Log4J1升级到Log4J2，现进行下总结。交代下技术背景：web项目，基于Java + Maven
1. 依赖
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.3</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.3</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.2</version>
</dependency>
<!-- slf4j到log4j2的桥梁 -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>2.3</version>
</dependency>
<!-- listener:Log4jServletContextListener依赖 -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-web</artifactId>
<version>2.3</version>
<scope>runtime</scope>
</dependency>
PS：slf4j-log4j12与log4j-slf4j-impl冲突，注意exclusion间接引入的slf4j-log4j12
2. 日志配置
配置log4j2.xml，放于classpath:log/log4j2.xml，或其他位置，则要注意修改下面web.xml中的响应配置
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="off">
<Appenders>
<Console name="STDOUT" target="SYSTEM_OUT">
<PatternLayout pattern="[%d] %-5p [%c %L] %m%n"/>
</Console>
<RollingFile name="AppAppender" fileName="/data/applogs/{项目名称}/logs/app.log"
filePattern="/data/applogs/{项目名称}/logs/app.log.%d{yyyy-MM-dd}">
<PatternLayout>
<Pattern>[%d] %-5p [%c %L] %m%n</Pattern>
</PatternLayout>
<Policies>
<!-- 每天切割日志 -->
<TimeBasedTriggeringPolicy interval="24" modulate="true"/>
</Policies>
</RollingFile>
</Appenders>
<Loggers>
<Root level="info">
<AppenderRef ref="STDOUT"/>
<AppenderRef ref="AppAppender"/>
</Root>
</Loggers>
</Configuration>
PS：
{项目名称} 需替换成自己的项目；
/data/applogs/{项目名称}/logs/app.log 设置日志文件的绝对路径
/data/applogs/{项目名称}/logs/app.log.%d{yyyy-MM-dd} 设置切割后日志的绝对路径
3. 读取配置
web.xml中增加读取log4j2.xml的配置：
<!--由Spring载入的Log4j配置文件位置 -->
<context-param>
<param-name>log4jConfiguration</param-name> <!-- log4j2.xml文件位置，注意与2中的相对应 -->
<param-value>classpath:log/log4j2.xml</param-value>
</context-param>
<!-- the very first listene -->
<listener>
<listener-class>org.apache.logging.log4j.web.Log4jServletContextListener</listener-class>
</listener>
4 参考资料
slf4j与jul、log4j1、log4j2、logback的集成原理