依赖

版本： 2.10.0

<!-- log4j 核心jar包 -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- log4j 核心jar包 -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 将 common-logging 的日志桥接到 log4j -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-jcl</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 将 log4j 1.x 的日志桥接到 log4j 2.x -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-1.2-api</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 将 java.util.logging 的日志桥接到 log4j 2.x -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-jul</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 将 slf4j 的日志桥接到 log4j 2.x。不要同时引用 log4j-to-slf4j -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>2.10.0</version>
</dependency>
<!-- 将 log4j 2.x 的日志桥接到 slf4j。不要同时引用 log4j-slf4j-impl -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-to-slf4j</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 在servlet或jsp容器中强烈建议引入该依赖，以解决log4j启动和卸载时的资源清理问题 -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-web</artifactId>
    <version>2.10.0</version>
</dependency>

配置

基本配置

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Properties>
        <!-- 自定义属性 -->
        <!-- 设置 log 目录 -->
        <Property name="log.dir">D:/logs/demo</Property>
        <!-- 设置日志文件编码 -->
        <Property name="charset.">D:/logs/demo</Property>
    </Properties>
    <Appenders>
        <!-- 控制台appender -->
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout charset="${log.charset}" pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %-5level %logger - %msg %ex %n"/>
        </Console>
        <RollingFile name="appFileLog" fileName="${log.dir}/app.log"
              filePattern="${log.dir}/%d{yyyy-MM-dd}/app.log">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %-5level %logger - %msg %ex %n"/>
            <Policies>
                <TimeBasedTriggeringPolicy />
            </Policies>
        </RollingFile>
    </Appenders>
    <Loggers>
        <!-- 默认日志级别 debug -->
        <Root level="debug">
            <!-- 默认日志输出到 控制台 -->
            <AppenderRef ref="Console"/>
            <AppenderRef ref="appFileLog" />
        </Root>
        <!-- 打印spring info日志 -->
        <logger name="org.springframework" level="info" />
    </Loggers>
</Configuration>

web环境配置

指定log4j日志配置文件

<context-param>
    <param-name>log4jConfiguration</param-name>
    <param-value>/WEB-INF/log4j.xml</param-value>
</context-param>

servlet 3.0

在servlet 3.0 环境中，log4j2 可以自动注册启动和卸载监听器。如果不需要自动注册，可以通过以下配置禁用。

<context-param>
    <param-name>isLog4jAutoInitializationDisabled</param-name>
    <param-value>true</param-value>
</context-param>

servlet 2.5

在servlet 2.5 环境中，必须手动指定 Log4jServletContextListener 以注册 log4j 启动和卸载监听器

<listener>
    <listener-class>org.apache.logging.log4j.web.Log4jServletContextListener</listener-class>
</listener>

使用

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
 
public class HelloWorld {
    private static final Logger logger = LogManager.getLogger("HelloWorld");
    public static void main(String[] args) {
        logger.info("Hello, World!");
        if (logger.isDebugEnabled()) {
          logger.debug("args[0]={}", args[0]);
        }
    }
}