如何简单使用log4j?

世界上并没有完美的程序，但是我们并不因此而沮丧，因为写程序就是一个不断追求完美的过程。

1. 引入依赖

<dependency>
  	<groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

2. 项目根目录中加入配置文件log4j.properties

### 设置###
log4j.rootLogger = debug,stdout

### 输出信息到控制抬 ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = [%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} %l%n%m%n

3. 使用

 public static void main(String[] args){
        Logger logger = Logger.getLogger(Demo1Test.class);
        logger.debug("hello");
        logger.info("hello");
        logger.warn("hello");
        logger.error("hello");
 }

运行结果：

[DEBUG] 2020-06-15 18:11:33,392 com.test.spring.Demo1Test.main(Demo1Test.java:19)
hello
[INFO ] 2020-06-15 18:11:33,395 com.test.spring.Demo1Test.main(Demo1Test.java:20)
hello
[WARN ] 2020-06-15 18:11:33,396 com.test.spring.Demo1Test.main(Demo1Test.java:21)
hello
[ERROR] 2020-06-15 18:11:33,396 com.test.spring.Demo1Test.main(Demo1Test.java:22)
hello