Java项目中 log4j的用法

1.在程序中导入jar:log4j-1.2.17.jar

2.新建文件log4j.properties放置在项目目录下,并增加代码行:

log4j.rootLogger=INFO,CONSOLE,DayRollingFile

#console

log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender

log4j.appender.Threshold=INFO

log4j.appender.CONSOLE.Target=System.out

log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout

log4j.appender.CONSOLE.layout.ConversionPattern=%d - %c -%-4r [%t] %-5p %x - %m%n

# dayrollingfile

log4j.appender.DayRollingFile=org.apache.log4j.DailyRollingFileAppender

log4j.appender.DayRollingFile.file=D:/logdir/项目名称_

log4j.appender.DayRollingFile.DatePattern=yyyyMMdd'.log'

log4j.appender.DayRollingFile.layout=org.apache.log4j.PatternLayout

log4j.appender.DayRollingFile.layout.ConversionPattern=/n/n[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n

3.在输出文件中添加代码行:

Logger logger = Logger.getLogger(Server.class); //Server为类名

PropertyConfigurator.configure("log4j.properties");

logger.info("hello!");

注意:当天生成的日志文件名为dtclient_,到第二天该日志文件名会自己改成dtclient_20160623.log

若遇到错误：

og4j:ERROR Could not read configuration file [log4j.properties].

log4j:ERROR Could not read configuration file [log4j.properties].

java.io.FileNotFoundException: log4j.properties (系统找不到指定的文件。)

at java.io.FileInputStream.open(Native Method)

at java.io.FileInputStream.<init>(FileInputStream.java:106) at java.io.FileInputStream.<init>(FileInputStream.java:66)

at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:306)

at org.apache.log4j.PropertyConfigurator.configure(PropertyConfigurator.java:324)

at snmp.GetSnmpInfo.<clinit>(GetSnmpInfo.java:32)

log4j:ERROR Ignoring configuration file [log4j.properties].

将log4j.properties 这个文件从src的根目录 转移到 项目的根目录下面