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This article introduces the relevant knowledge of "how to solve the problem of relative path in Log4j". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. In properties file:

Log4j.appender.logfile.File=$ {WORKDIR} / logs/app.log

Where "${WORKDIR} /" is a variable and will be replaced by the value of "WORKDIR" in System Property. In this way, we can set the root path with System.setProperty before log4j loads the configuration file.

In jsp, you can do this:

String path = pageContext.getServletContext () .getRealPath ("/")

String realPath = path+ "WEB-INFclasseslog4j.properties"

System.setProperty ("WORKDIR", path.replace ("," / "))

PropertyConfigurator.configure (realPath.replace ("", "/")); / / load the .properties file

[@ more@]

Second, you can use environmental variables (I have never tried to read it online)

Log4j.appender.R=org.apache.log4j.RollingFileAppender

Log4j.appender.R.File=$ {catalina.base} / logs/logs_tomcat.log

Log4j.appender.R.MaxFileSize=10KB

Third, the concrete realization: (I have not tried to read it on the Internet)

Generally speaking, in the course of our development project, the output path of the log4j log is fixed to a certain folder, so if I change the environment, the log path needs to be modified again, which is not convenient. At present, I use the method of dynamically changing the log path to save the log file relative to the path.

(1)。 When the project starts, load the initialization class:

Public class Log4jInit extends HttpServlet {

Static Logger logger = Logger.getLogger (Log4jInit.class)

Public Log4jInit () {}

Public void init (ServletConfig config) throws ServletException {

String prefix = config.getServletContext () .getRealPath ("/")

String file = config.getInitParameter ("log4j")

String filePath = prefix + file

Properties props = new Properties ()

Try {

FileInputStream istream = new FileInputStream (filePath)

Props.load (istream)

Istream.close ()

/ / toPrint (props.getProperty ("log4j.appender.file.File"))

String logFile = prefix + props.getProperty ("log4j.appender.file.File"); / / set the path

Props.setProperty ("log4j.appender.file.File", logFile); PropertyConfigurator.configure (props)

/ / load log4j configuration information

} catch (IOException e) {

ToPrint ("Could not read configuration file [" + filePath + "].")

ToPrint ("Ignoring configuration file [" + filePath + "].")

Return

}

}

Public static void toPrint (String content) {

System.out.println (content)

}

}

(2) configuration in .Web.xml

Log4j-init

Log4jInit

Log4j

WEB-INF/classes/log4j.properties

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