以编程方式覆盖log4j配置：FileAppender的文件位置

要在运行时更改log4j属性，请访问此链接

http://alperkaratepe.wordpress.com/2010/01/16/how-to-change-log4j-properties-
at-runtime/

 private void updateLog4jConfiguration(String logFile) {     Properties props = new Properties();     try {         InputStream configStream = getClass().getResourceAsStream( "/log4j.properties");         props.load(configStream);         configStream.close();     } catch (IOException e) {         System.out.println("Error: Cannot laod configuration file ");     }     props.setProperty("log4j.appender.FILE.file", logFile);     PropertyConfigurator.configure(props);  }