整理自网上:
一般在我们开发项目过程中,log4j日志输出路径固定到某个文件夹,这样如果我换一个环境,日志路径又需要重新修改,比较不方便,
1.log4j的FileAppender本身就有这样的机制,
如:log4j.appender.logfile.File=${WORKDIR}/logs/app.log
其中“${WORKDIR}/”是个变量,会被System Property中的“WORKDIR”的值代替。这样,我们就可以在log4j加载配置文件之前,先用System.setProperty设置好根路径。
在 没有发现这个技巧之前,为了解决这个问题,我曾自己扩展了log4j的RollingFileAppender类,其他的FileAppender同样道 理。
扩展的方法,就是用一个子类去覆盖setFile方法,这个方法在log4j读取配置文件生成appender的时候调用,传入的就是配置文件中的路 径,这样我就可以按照自己的想法在路径前面加上根路径了。
2.可以使用环境变量,(一般比较方便的配置)
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=${catalina.base}/logs/logs_tomcat.log
log4j.appender.R.MaxFileSize=10KB
3.自定义实现:
(1).在项目启动时,装入初始化类:
1 public class Log4jInit extends HttpServlet {
2 static Logger logger = Logger.getLogger(Log4jInit.class);
3
4 public Log4jInit() {
5 }
6
7 public void init(ServletConfig config) throws ServletException {
8 String prefix = config.getServletContext().getRealPath("/");
9 String file = config.getInitParameter("log4j");
10 String filePath = prefix + file;
11 Properties props = new Properties();
12 try {
13 FileInputStream istream = new FileInputStream(filePath);
14 props.load(istream);
15 istream.close();
16 //toPrint(props.getProperty("log4j.appender.file.File"));
17 String logFile = prefix + props.getProperty("log4j.appender.file.File");//设置路径
18 props.setProperty("log4j.appender.file.File",logFile);
19 PropertyConfigurator.configure(props);//装入log4j配置信息
20 } catch (IOException e) {
21 toPrint("Could not read configuration file [" + filePath + "].");
22 toPrint("Ignoring configuration file [" + filePath + "].");
23 return;
24 }
25
26 }
27
28 public static void toPrint(String content) {
29 System.out.println(content);
30 }
31
32 }
2 static Logger logger = Logger.getLogger(Log4jInit.class);
3
4 public Log4jInit() {
5 }
6
7 public void init(ServletConfig config) throws ServletException {
8 String prefix = config.getServletContext().getRealPath("/");
9 String file = config.getInitParameter("log4j");
10 String filePath = prefix + file;
11 Properties props = new Properties();
12 try {
13 FileInputStream istream = new FileInputStream(filePath);
14 props.load(istream);
15 istream.close();
16 //toPrint(props.getProperty("log4j.appender.file.File"));
17 String logFile = prefix + props.getProperty("log4j.appender.file.File");//设置路径
18 props.setProperty("log4j.appender.file.File",logFile);
19 PropertyConfigurator.configure(props);//装入log4j配置信息
20 } catch (IOException e) {
21 toPrint("Could not read configuration file [" + filePath + "].");
22 toPrint("Ignoring configuration file [" + filePath + "].");
23 return;
24 }
25
26 }
27
28 public static void toPrint(String content) {
29 System.out.println(content);
30 }
31
32 }
Web.xml中的配置
1 <servlet>
2 <servlet-name>log4j-init</servlet-name>
3 <servlet-class>Log4jInit</servlet-class>
4 <init-param>
5 <param-name>log4j</param-name>
6 <param-value>WEB-INF/classes/log4j.properties</param-value>
7 </init-param>
8 <load-on-startup>1</load-on-startup>
9 </servlet>
2 <servlet-name>log4j-init</servlet-name>
3 <servlet-class>Log4jInit</servlet-class>
4 <init-param>
5 <param-name>log4j</param-name>
6 <param-value>WEB-INF/classes/log4j.properties</param-value>
7 </init-param>
8 <load-on-startup>1</load-on-startup>
9 </servlet>