加载lo4j.properties日志文件

1、看下我的工程项目目录结构(maven工程，资源文件一般都是放在src/main/resources目录下,如果是非maven的java工程放到src根目录下就可以)

2、maven工程配置文件pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>hello</groupId>
	<artifactId>test</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>
	<name>test</name>
	<url>http://maven.apache.org</url>
	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>
		<!-- slf4j -->
		<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>1.5.5</version>
		</dependency>

	</dependencies>
</project>

 

3、代码

public class TestLog {
	
	public static final Logger log = LoggerFactory.getLogger(TestLog.class);
	
	public static void main(String[] args) {
		//int count = 0;
		log.info("-------begin----");
		//if(log.isDebugEnabled()){
		//	log.debug("debug");
		//}
		log.debug("debug{}");
		log.info("-------end------");
		
	}
}

 

4、但是有时候我们需要把log4j.properties日志配置文件放到指定的目录下，比如工程目录下的cfg目录下,把log4j.properties文件移到cfg目录下，出现以下错误

log4j:WARN No appenders could be found for logger (hello.test.TestLog).
log4j:WARN Please initialize the log4j system properly.

 5、根据以上信息是没有找到log4j.properties文件,修改下代码就可以了

public static void main(String[] args) {
		PropertyConfigurator.configure("./cfg/log4j.properties");//指定日志配置文件的路径
		//int count = 0;
		log.info("-------begin----");
		//if(log.isDebugEnabled()){
		//	log.debug("debug");
		//}
		log.debug("debug{}");
		log.info("-------end------");
		
	}

 6、输出结果

2017-07-31 22:47:48,662-5p TestLog  - -------begin----
2017-07-31 22:47:48,665-5p TestLog  - debug{}
2017-07-31 22:47:48,665-5p TestLog  - -------end------