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Log4j Examples

static final Logger logger=Logger.getLogger(HelloWorld.class);
public static void main(String args[]) throws IOException
    {
    FileAppender fileAppender=new FileAppender(new PatternLayout(),"service.txt");
        logger.addAppender(fileAppender);
        BasicConfigurator.configure();
        logger.debug("Debug Message."); 
        logger.info("Info Message.");
}

This function will write logs messages in 'service.txt' file.
for this purspose you need to have log4j.properties file configured as

log4j.appender.rollingFile=org.apache.log4j.RollingFileAppender
log4j.appender.rollingFile.File=/data/dev/newworkspace/log4jTry/src/com/anm/log/log.txt
log4j.appender.rollingFile.MaxFileSize=2MB
log4j.appender.rollingFile.MaxBackupIndex=2
log4j.appender.rollingFile.layout = org.apache.log4j.PatternLayout
log4j.appender.rollingFile.layout.ConversionPattern=%p %t %c - %m%n
log4j.rootLogger = INFO, rollingFile

ans by 4p3

// program by Nishanth Thomas - InSolutions Global Bangalore

// example class file

package com.logs;

import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date;

import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpSession;

import org.apache.log4j.BasicConfigurator; import org.apache.log4j.FileAppender;

import org.apache.log4j.Logger; import org.apache.log4j.PatternLayout;

import org.apache.log4j.PropertyConfigurator; import org.apache.log4j.xml.DOMConfigurator;

public class Logscollected {

  static Logger log = Logger.getLogger(Logscollected.class);

public static void logscollection(Exception e, HttpServletRequest request) throws IOException{

  HttpSession session = request.getSession();

    String  exceptiondetail = â??â?? ;

     //create a folder in your application config and place log4j.xml file there  and       
               // get path by the following;

      String strPath =  request.getRealPath("config");

      DOMConfigurator.configure(strPath+"/"+"log4jexp.xml");

      //create log4j.xml file as give name like  shown above log4jexp;

 try{

      ////  /* Get the Stack Trace messages //////
      e = ((e==null)?((Exception)request.getAttribute("Exception")):e);

        StackTraceElement stem[]=e.getStackTrace();

  for(int i=0;i<stem.length;i++){
        if (!exceptiondetail.equals(""))
                    exceptiondetail += "\n";
                exceptiondetail += "\t";

    exceptiondetail=exceptiondetail+stem[i].toString();

       }

          log.debug(exceptiondetail);
                  //log.info(e);
                    // log.warn("Here is some WARN");
                    //  log.info(object);
          log.error(e);

          //  log.fatal("Here is some FATAL");

    }catch(Exception e1){
        e1.printStackTrace();
    }
  }

}

In the catch of any servlet call that function like this

 try{

//     Some code����

 }

 catch(Exception e)
    {

                // Logs collection log 4j------------------------

        Logscollected.logscollection(e,request);

        //---------------------------

   }

Now Finally

Lo4j.xml here we renamed to log4jexp.xml to avoid conflicts with server log4j.xml file palce log4jexp.xml in config folder ( here I used)

<--configure path according to your requrmts to save log file -->

<appender name="daoAppender" 
   class="org.apache.log4j.RollingFileAppender">   
    <param name="maxFileSize" value="100KB" />   
    <param name="maxBackupIndex" value="2" />   
    <param name="File" value="${jboss.server.home.dir}/deploy/myexampleprj.war/serverlogs/serverlogs.txt" />   
    <layout class="org.apache.log4j.PatternLayout">   
        <param name="ConversionPattern"  
               value="%d{dd-MMM-yyyy HH:mm};%5p %c %m%n" />   
    </layout>   
</appender>   

  <--configure path according for diff packge to your requrmts to save log file -->   

<!--appender name="appAppender"  
          class="org.apache.log4j.RollingFileAppender">   
    <param name="maxFileSize" value="100KB" />   
    <param name="maxBackupIndex" value="2" />   
    <param name="File" value="${jboss.server.home.dir}/deploy/myexampleprj.war/serverlogs/serverlogs.txt" />   
    <layout class="org.apache.log4j.PatternLayout">   
        <param name="ConversionPattern"  
               value="%d{ABSOLUTE} %5p %c{1}: %m%n " />   
    </layout>    
</appender-->   

<!â??package name given in category here com is the package give package name  -->    

<!--category name="com.ex.actions">     
    <priority value="DEBUG"/>     
    <appender-ref ref="appAppender"/>       
</category-->

<category name="com">     
    <priority value="DEBUG"/>     
    <appender-ref ref="daoAppender"/>       
</category>    

<root>   
    <!--     
    <appender-ref ref="appAppender" />   
    <appender-ref ref="daoAppender" />   
    -->    
</root>