http://www.codeceo.com/article/log4j-usage.html

获取构造器和记录日志：

public class a{    private static final Logger logger = Logger.getLogger(a.class);    public void testLog(){                   SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd");        try {              sdf.parse("");        } catch (ParseException e) {             logger.fatal("testLog method log:"+ex.getMessage());            }    }}