Java log4j usage details (SSH, SSM framework)

What is log4j?

Log4j is an open source project of Apache . By using Log4j, we can control the destination of log information delivery to consoles , files, GUI components, and even socket servers, NT event loggers, UNIX Syslog daemons , etc.; we also The output format of each log can be controlled; by defining the level of each log information, we can control the log generation process in more detail. Most interestingly, these can be flexibly configured via a configuration file without modifying the application code.

1. Introduce log4j

There are two ways to use log4j

1. Introduce the corresponding Jar package

Add log4j-1.2.8.jar (you can choose a later version of log4j) to lib.

2. Using Maven

<!-- Add log4j support-->
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

2. Placement log4j.properties

Take the SSH framework as an example, create a log4j.properties

log4j.rootLogger = debug,stdout,D,E  
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} method:%l%n%m%n  
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender  
log4j.appender.D.File = D://logs/log.log  
log4j.appender.D.Append = true  
log4j.appender.D.Threshold = DEBUG   


log4j.appender.D.layout = org.apache.log4j.PatternLayout  
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n  
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender  
log4j.appender.E.File =D://logs/error.log   
log4j.appender.E.Append = true  
log4j.appender.E.Threshold = ERROR   
log4j.appender.E.layout = org.apache.log4j.PatternLayout  
log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n

3. Add the following content in web.xml

<context-param>
  <param-name>webAppRootKey</param-name>
  <param-value>webapp.root</param-value>
</context-param>
<context-param>
  <param-name>log4jConfigLocation</param-name>
  <param-value>classpath:log4j.properties</param-value>
</context-param>
<context-param>
  <param-name>log4jRefreshInterval</param-name>
  <param-value>3000</param-value>
</context-param>
<listener>
  <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>

四.如何使用

private static Logger logger = Logger.getLogger(XXX.class);

该语句获得了一个Logger,然后在需要输出日志的地方

Logger.debug ( Object message ) ;
Logger.info ( Object message ) ;
Logger.warn ( Object message ) ;
Logger.error ( Object message ) ;

#日志等级

#TRACE：详细等级，堆栈信息
#debug：类似于System.out.print
#info：类似于Hibernate的show_sql
#warn：不影响运行， 只是提示
#error：出现异常

四条语句对应了4个不同的级别,debug的级别最低,error级别最高,Threshold如果设置成DEBUG,则4个级别只会输出error级别.

Java log4j usage details (SSH, SSM framework)

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