Log4J的使用

1.首先導入log4j的包

2.寫log4j.properties文件

### set log levels ### log4j.rootLogger = DEBUG , stdout , D , E ### to console ### 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 = %d{ABSOLUTE} %5p %l - %m%n ### to file ### log4j.appender.D = org.apache.log4j.DailyRollingFileAppender log4j.appender.D.File = setup log4j.appender.D.Threshold = DEBUG log4j.appender.D.Append = true 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 ### error to file ### log4j.appender.E = org.apache.log4j.DailyRollingFileAppender log4j.appender.E.File = setup log4j.appender.E.Threshold = WARN log4j.appender.E.Append = true 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

輸出到控制檯，文件，警告以上的信息輸出到單獨的文件。File的屬性隨便寫的，不能寫死，在後面配置。

3.創建LogListener監聽器類

package listener; import java.io.FileInputStream; import java.io.IOException; import java.util.Properties; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import org.apache.log4j.Logger; import org.apache.log4j.PropertyConfigurator; public class LogListener extends HttpServlet { private static final long serialVersionUID = 1L; static Logger log = Logger.getLogger(LogListener.class); public LogListener() { } public void init(ServletConfig config) throws ServletException { String prefix = config.getServletContext().getRealPath("/"); String properties = config.getInitParameter("log4j_properties"); String logger = config.getInitParameter("logFile"); String errors = config.getInitParameter("errorFile"); String logFile = (prefix + logger).replace('//', '/');// 設置日誌文件路徑 String errorFile = (prefix + errors).replace('//', '/');//錯誤日誌文件路徑 String propertiesPath = prefix + properties; Properties props = new Properties(); try { FileInputStream istream = new FileInputStream(propertiesPath); props.load(istream); istream.close(); props.setProperty("log4j.appender.D.File", logFile); props.setProperty("log4j.appender.E.File", errorFile); PropertyConfigurator.configure(props);// 裝入log4j配置信息 log.info("LOG被加載 日誌文件位置：" + props.getProperty("log4j.appender.D.File")); log.info("error LOG被加載 日誌文件位置：" + props.getProperty("log4j.appender.E.File")); } catch (IOException ioe) { log.error(ioe); return; } } }

4.在web.xml中配置一下

<servlet> <servlet-name>LogListener</servlet-name> <servlet-class>listener.LogListener</servlet-class> <init-param> <param-name>log4j_properties</param-name> <param-value>WEB-INF/classes/log4j.properties</param-value> </init-param> <init-param> <param-name>logFile</param-name> <param-value>logs/log.log</param-value> </init-param> <init-param> <param-name>errorFile</param-name> <param-value>logs/error.log</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet>

然後就可以使用日誌了。

在類中使用如下：

private static Logger log = Logger.getLogger(DataManager.class.getName());

log.error("");

log.warn("");

log.info("");

log.debug("");

這四種就夠了，層次由高到低。