CODEWITHSUNDEEP
javahtmljspservlets
iika-
iika-

Reputation: 91

Getting NullPointerException while executing display JSP page using servlets

I am trying to display details of a user from the database. Getting NullPointerException Below are my Jsp and Servlet Pages

Also I am new to it,so there must be some silly mistake I guess.

JSP Page

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" isELIgnored="false"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>View Profile</title>
</head>
<html>  
<body>  
<form action="ProfileServlet?ac=view">  
Enter your username:<input type=text name=username><br/>  
  
<input type=submit value=Submit>  
</form>  
</body>  
</html>

Servlet

package com.Webhtml.controller;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*; 
  
public class ProfileServlet extends HttpServlet {  
  
public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
    
String a=request.getParameter("ac");    
response.setContentType("text/html");  
PrintWriter out = response.getWriter();  
if(a.equals("view")) {
String username=request.getParameter("username");
          
try{  
Class.forName("com.mysql.jdbc.Driver");  
Connection con=DriverManager.getConnection("jdbc:mysql://75.20.205.173:3306/,"contact","root","root");  
              
PreparedStatement ps=con.prepareStatement("select * from user where username=?");  
ps.setString(13,username);  
              
out.print("<table width=50% border=1>");  
out.print("<caption>Result:</caption>");  
  
ResultSet rs=ps.executeQuery();  
              
/* Printing column names */  
ResultSetMetaData rsmd=rs.getMetaData();  
int total=rsmd.getColumnCount();  
out.print("<tr>");  
for(int i=1;i<=total;i++)  
{  
out.print("<th>"+rsmd.getColumnName(i)+"</th>");  
}  
  
out.print("</tr>");  
              
/* Printing result */  
  
while(rs.next())  
{  
out.print("<tr><td>"+rs.getString(2)+ "</td><td>"+rs.getString(3)+"</td><td>"+rs.getLong(4)+"</td><td>"+rs.getString(5)+"</td><td>"+rs.getDate(6)+"</td><td>"+rs.getString(7)+"</td><td>"+rs.getString(8)+"</td><td>"+rs.getString(9)+"</td><td>"+rs.getString(10)+"</td><td>"+rs.getString(11)+"</td></tr>");  
                  
}  
  
out.print("</table>");  
              
}catch (Exception e2) {e2.printStackTrace();}  
          
finally{out.close();}  

}
}  
}

Error

Sep 20, 2021 7:31:29 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [ProfileServlet] in context with path [/Webhtml] threw exception
java.lang.NullPointerException
    at com.Webhtml.controller.ProfileServlet.doGet(ProfileServlet.java:20)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:500)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

Upvotes: 0

Views: 40

Answers (1)

Miguel Angel Muela
Miguel Angel Muela

Reputation: 36

You are not performing null checks in the variable "a". This variable is a parameter, can be null, so your code crashes at :

if(a.equals("view"))

Because a in this case is null.

Why "a" is null? maybe you need to specify the params inside an input type hidden inside the form instead of putting them directly in the action of the form:

<form action="ProfileServlet">  
   Enter your username:<input type=text name=username><br/>  
   <input type="hidden" id="ac" name="ac" value="view">
   <input type=submit value=Submit>  
</form>

Upvotes: 1

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