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Context Log Example Using Servlet


This example illustrates about how to use of Context Log in servlet. Context Log is used to write specified message to server log file when servlet is called. In the following JSP page (message.jsp) we have simply taken a text area where user give his/her message and post the form. After posting the form, the servlet ContextLogExample is called. Source code of the message.jsp is given below:




Source code of message.jsp:

<%@page language="java" session="true" contentType="text/html;charset=ISO-8859-1"%> 
<form name="frm" method="post" action=../ContextLogExample>
    <table border = "0">
        <tr align="left" valign="top">
            <td>Give your Message:</td>
            <td><TEXTAREA NAME="message" COLS=30 ROWS=6></TEXTAREA></td>
        <tr align="left" valign="top">
            <td><input type="submit" name="submit" value="submit"/></td>

Running the jsp page (message.jsp) on this url: http://localhost:8080/JavaExample/JSP/message.jsp 
the will displays as below:

In the following servlet  (ContextLogExample) we get parameter of jsp page in "message" variable and set this message to the log file by log() method of ServletContext interface

The Source code of ContextLogExample.java is given below:

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ContextLogExample extends HttpServlet {
  public void doPost(HttpServletRequest request, 
HttpServletResponse response
throws ServletException, IOException{
    PrintWriter out = response.getWriter();
    String message = request.getParameter("message");
    ServletContext context = getServletContext();
    if(message == null || message.equals("")){
      context.log("No message received:"
IllegalStateException("Parameter not Found"));
      context.log("Parameter Found: Successfully 
received your message: " 
+ message);
    out.println("<html><head><title>Context Log 
    out.println("<h2><font color='green'>Successfully 
send your Message</font></h2>"

Mapping of servlet (ContextLogExample.java) in web.xml


User enters the  message in the text area that is sent to the servlet (ContextLogExample)

Servlet sets the message in the log file which is shown like below:

Download Source Code


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