匯入log4j-1.2.7.jar和commons-logging-api-1.1.jar（版本沒有規定）

新建log4j.properties配置檔案，內容如下:

log4j.rootLogger=ALL, CA ,file

# ConsoleAppender
log4j.appender.CA=org.apache.log4j.ConsoleAppender
log4j.appender.CA.layout=org.apache.log4j.PatternLayout
log4j.appender.CA.layout.ConversionPattern= %d{yyyy-MM-dd HH:mm:ss} %5p %c %t: - %m%n

# FileAppender
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=${catalina.home}/logs/ddoMsg.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern= %d{yyyy-MM-dd HH:mm:ss} %5p %c %t: - %m%n

log4j.properties檔案放在專案名/src檔案下。

java程式碼如下:

package com;

import org.apache.log4j.Logger;

public class test01 {

private static Logger logger = Logger.getLogger(test01.class);

public static void main(String[] args) {
//輸出等級由小到大
logger.debug("****** debug start ****** ");
logger.info("****** info start ****** ");
logger.warn("****** warn start ****** ");
logger.error("****** error start ****** ");
logger.fatal("****** fatal start ****** ");
}
}