整合log4j日志

1. 优先级
   1. TRACE<DEBUG<INFO<WARN<ERROR<FATAL
   2. 级别高的会自动屏蔽级别低的日志,假如设置级别为INFO,TRACE及DEBUG都不显示
2. 可以设置日志输出目的地
3. 可以配置日志输出格式化
4. 使用
   1. 引入依赖

           <dependency>
               <groupId>org.apache.logging.log4j</groupId>
               <artifactId>log4j-core</artifactId>
               <version>2.19.0</version>
           </dependency>
           <dependency>
               <groupId>org.apache.logging.log4j</groupId>
               <artifactId>log4j-slf4j2-impl</artifactId>
               <version>2.19.0</version>
           </dependency>

   2. 极简配置log4j2.xml

   <?xml version="1.0" encoding="UTF-8"?>
   <Configuration status="WARN">
       <Appenders>
           <Console name="Console" target="SYSTEM_OUT">
               <PatternLayout pattern="%d{MM/dd HH:mm:ss} [%t] %-5level %logger{36} - %msg%n"/>
           </Console>
       </Appenders>
       <Loggers>
           <Root level="DEBUG">
               <AppenderRef ref="Console"/>
           </Root>
       </Loggers>
   </Configuration>

5. 重新运行test方法,输出:

12/13 11:34:35 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3eb77ea8
12/13 11:34:35 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 1 bean definitions from class path resource [bean.xml]
12/13 11:34:35 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'user'

6. 分析
   1. 刷新容器
   2. bean.xml加载1个bean的定义
   3. 创建了一个单例的user对象