使用Slf4j集成Log4j2

1. 添加slf4j和log4j2的依赖

<properties>
    <log4j.version>2.5</log4j.version>
</properties>

<dependencies>
     <!-- slf4j + log4j2 begin -->
    <!-- slf4j核心包-->
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.13</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>jcl-over-slf4j</artifactId>
        <version>1.7.13</version>
        <scope>runtime</scope>
    </dependency>
    <!--用于与slf4j保持桥接-->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j-impl</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <!-- 桥接：告诉commons logging使用Log4j2 -->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-jcl</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <!-- log4j2 核心包-->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <!--web工程需要包含log4j-web，非web工程不需要, 感觉可有可无-->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-web</artifactId>
        <version>2.4.1</version>
        <scope>runtime</scope>
    </dependency>
    <!--需要使用log4j2的AsyncLogger需要包含disruptor-->
    <dependency>
        <groupId>com.lmax</groupId>
        <artifactId>disruptor</artifactId>
        <version>3.2.0</version>
    </dependency>
    <!-- log4j end-->
</dependencies>

2. web.xml中设置log4j2的监听器和过滤器

注意：servlet3.0及以上版本不需要该步操作

<!--对于log4j2，Servlet2.5以前的版本需要-->
<listener>
    <listener-class>org.apache.logging.log4j.web.Log4jServletContextListener</listener-class>
</listener>
<filter>
    <filter-name>log4jServletFilter</filter-name>
    <filter-class>org.apache.logging.log4j.web.Log4jServletFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>log4jServletFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>INCLUDE</dispatcher>
    <dispatcher>ERROR</dispatcher>
</filter-mapping>

注意：log4j2不指定位置的情况下默认在src/main/resources下查找。

如果需要自定义位置，需要在上面的web.xml中添加以下代码

<context-param>  
   <param-name>log4jConfiguration</param-name>  
   <param-value>/WEB-INF/classes/log4j2.xml</param-value>  
</context-param>