springBoot: 引入log4j2日志时报错！

Problem：

引入log4j2日志配置时报错:

Logging system failed to initialize using configuration from 'classpath:log4j2.xml'
java.lang.IllegalStateException: Logback configuration error detected: 

Solution：

实际上是pom中jar包冲突的问题！

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
	<exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

注意：
不能仅在starter-web中除去(exclusions) logging！其他dependency中也可能默认配置了logging！

所以，要直接在根starter中除去(exclusions)！

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>