log4j配置

添加jar包，log4j-1.2.17.jar
写配置文件，log4j.properties
创建一个log4j对象

log4j.rootLogger =debug,stdout
log4j.logger.com.mingsoft=debug
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern =  %d{ABSOLUTE} %5p %c{1}:%L - %m%n

private static Logger logger = Logger.getLogger(“你的类名”.class);
logger.debug(“hello world!”);