One: Introduction
LOG4J is a Jakarta project is mainly for debugging use, in order not to let is in the program to write a lot of System.out.println ();
I personally think is a good tool, the program after debugging, you can turn off the log4j.
Two: Download
You can download from the address below to ant, current version: 1.13
http://jakarta.apache.org/builds/jakarta-log4j/release/v1.1.3/
Three: Installation
log4j do not need to install, you only need to put Log4j.jar,log4j-core.jar in the classpath you can use.
IV: Using LOG4J
1: Copy Log4j.jar,log4j-core.jar to Classpath, in tomcat4.03 you can put it in
The Tomcat_home\common\lib directory.
2: Set the properties file
Log4j need to use a log4j.properties file with the following contents:
Log4j.properties
=====================================
log4j.rootcategory=, A1
Log4j.appender.a1.layout=org.apache.log4j.patternlayout
The simplest configuration, if you want to be complex, look at the document yourself.
3: Write Startup file
There are several ways to initialize log4j, and I only provide one way below.
Initservlet.java (a servlet)
==================================
Import Java.io.InputStream;
Import java.io.IOException;
Import java.util.Hashtable;
Import Java.util.Locale;
Import java.util.MissingResourceException;
Import Javax.servlet.RequestDispatcher;
Import javax.servlet.ServletException;
Import javax.servlet.UnavailableException;
Import Javax.servlet.http.HttpServlet;
Import Javax.servlet.http.HttpServletRequest;
Import Javax.servlet.http.HttpServletResponse;
Import javax.servlet.http.HttpSession;
Import javax.servlet.*;
Import java.io.*;
public class Initservlet extends HttpServlet {
Protected String config = "/log4j.properties";
public void Init () throws Servletexception {
ServletContext SCT = Getservletcontext ();
System.out.println ("[log4j]: The Root Path:" + sct.getrealpath ("/"));
System.out.println ("[log4j]: Initservlet init start ...");
Org.apache.log4j.PropertyConfigurator.configure (Sct.getrealpath ("/") + Getservletconfig (). Getinitparameter (" Log4j "));
System.out.println ("[log4j]: Initservlet init over.");
}
public void doget (HttpServletRequest request,
HttpServletResponse response)
Throws IOException, Servletexception {
;
}
public void DoPost (HttpServletRequest request,
HttpServletResponse response)
Throws IOException, Servletexception {
;
}
}
4: Set Web.xml
The servlet that is written above is appserver to run, so you need to configure the Web.xml
Add the following content:
<servlet>
<servlet-name>init</servlet-name>
<servlet-class>com. Initservlet</servlet-class>
<init-param>
<param-name>log4j</param-name>
<param-value>/log4j.properties</param-value>
<!--the relative aplication path is above root/log4j.properties reference-->
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
5: Use log4j in the program;
private static Org.apache.log4j.Category log =
Org.apache.log4j.Category.getInstance (classname);
ClassName Java filename \ r
Log.debug ("...");
Log.error ("...");
.....
You can look at log4j's documents in concrete use.
