How to log logs using log4j

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1. Why does the logger log not print?
Answer: (1) need to include the log package in the Resin_homg\lib directory, such as: Log4j-1.2.8.jar,commons-logging.jar;
(2) required in the Web-info\classes\ directory must contain: Commons-logging.properties and log4j.properties these two documents;
(3) The contents of the Commons-logging.properties file are as follows: If the log4j logger is used then it must be written as: org.apache.commons.logging.log= Org.apache.commons.logging.impl.Log4JLogger
# #set Log as log4j
Org.apache.commons.logging.log=org.apache.commons.logging.impl.log4jlogger

# # Set Log as Simplelog
#org. Apache.commons.logging.log=org.apache.commons.logging.impl.simplelog
(4) You need to configure initialization log4j in Web. xml:
(5) There are several ways to use Cheng:
The first way:
Importorg.apache.log4j.Logger;
privatestatic Logger Logger = Logger.getlogger (Loginaction.class);
Logger.info ("Now enter Loginaction:execute () method!");
The second way:
Importorg.apache.log4j.Category;
Privatestatic categorylogger=category.getinstance (Loginaction.class);
Logger.info ("Now enter Loginaction:execute () method!");
The Third Way:
Importorg.apache.commons.logging.Log;
Importorg.apache.commons.logging.LogFactory;
Privatestatic Log Logger=logfactory.getlog (loginaction.class);
Logger.info ("Now enter Loginaction:execute () method!");
*******************************************************************************************
See below for details:
One: Introduction
Log4j is a project of Jakarta is mainly for debugging use, in order not to let is written in the program a lot of System.out.println ();
I personally think is a good tool, the program after debugging you can turn off log4j.
Two: Download
You can download it from the address below to ant, current version: 1.13
http://jakarta.apache.org/builds/jakarta-log4j/release/v1.1.3/

Three: Installation
LOG4J does not need to be installed, you only need to put Log4j.jar,log4j-core.jar in classpath you can use.

Four: Using log4j
1:) Copylog4j.jar,log4j-core.jar to Classpath, in tomcat4.03 you can put it in
The Tomcat_home\common\lib directory.
2: Set Properties file
Log4j need to use a log4j.properties file content as follows:
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 offer one way below.
Initservlet.java (a servlet)
==================================
Importjava.io.InputStream;
Importjava.io.IOException;
importjava.util.Hashtable;
Importjava.util.Locale;
Importjava.util.MissingResourceException;
Importjavax.servlet.RequestDispatcher;
Importjavax.servlet.ServletException;
Importjavax.servlet.UnavailableException;
Importjavax.servlet.http.HttpServlet;
Importjavax.servlet.http.HttpServletRequest;
Importjavax.servlet.http.HttpServletResponse;
Importjavax.servlet.http.HttpSession;
importjavax.servlet.*;
importjava.io.*;

Public Classinitservlet 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)