Getting NullPointerException

Hi All
I have written a Servlet program and a JSP program. When I'm trying to execute on Tomcat, am getting a NullPointerException. I'm not able to identify the problem. Here's the program:

RegServlet.java

package com.dbentry.servlet;
 
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
 
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class RegServlet extends HttpServlet {
PreparedStatement pstmt;
Connection con;
 
private static final long serialVersionUID = 1L;
public RegServlet() {
super();
 
}
 
public void init(ServletConfig config) throws ServletException {
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql:///test", "root",
"Varshini@9");
pstmt = con.prepareStatement("INSERT INTO reg VALUES(?,?,?,?)");
} catch (Exception e) {
 
}
 
}
 
public void destroy() {
try {
pstmt.close();
con.close();
} catch (Exception e) {
// e.printStackTrace();
}
 
}
 
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
int regid = Integer.parseInt(request.getParameter("regid").trim());
String name = request.getParameter("name").trim();
String email = request.getParameter("email").trim();
String mobile = request.getParameter("mobile").trim();
 
try {
pstmt.setInt(1, regid);
pstmt.setString(2, name);
pstmt.setString(3, email);
pstmt.setString(4, mobile);
 
out.println("Record inserted successfully");
} catch (SQLException e) {
out.println("Record insertion failed");
}
 
}
 
}

Reg.jsp :

Can anyone tell where the program fails?

Thanks...!

I forgot to mention, the JSP is working fine, i.e , I'm able to enter data on the JSP page but when I click on Submit I'm getting NullPointerException. And the database fields also match....not able to trace out the problem...

Do you not think that letting us know which line is generating the NPE would be a good idea?

Can you post your error message (Exception call stack)?

Sorry for not posting the stack trace earlier.....

This is what I get when I run the JSP on the Tomcat(after submitting the data).

java.lang.NullPointerException
        at com.dbentry.servlet.RegServlet.destroy(RegServlet.java:72)
        at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:
1393)
        at org.apache.catalina.core.StandardWrapper.stop(StandardWrapper.java:17
38)
        at org.apache.catalina.core.StandardContext.stop(StandardContext.java:45
09)
        at org.apache.catalina.core.ContainerBase.removeChild(ContainerBase.java
:924)
        at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java
:1006)
        at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1214)
        at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java
:293)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(Lifecycl
eSupport.java:117)
        at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBas
e.java:1337)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.p
rocessChildren(ContainerBase.java:1601)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.p
rocessChildren(ContainerBase.java:1610)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.r
un(ContainerBase.java:1590)
        at java.lang.Thread.run(Unknown Source)
Dec 5, 2008 6:00:39 PM org.apache.catalina.startup.HostConfig deployWAR
INFO: Deploying web application archive Harsha.war
Dec 5, 2008 6:01:29 PM org.apache.catalina.startup.HostConfig checkResources

And I'm getting this message on the Tomcat console.

I think there is a problem when loading your JDBC driver:

1. try to print out the stack trace in init() method:
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql:///test", "root","Varshini@9");
pstmt = con.prepareStatement("INSERT INTO reg VALUES(?,?,?,?)");
} catch (Exception e) {
e.printStackTrace(System.err); //add this line and run again
}

2. if you want to insert records into your database,
you need to invoke the executeUpdate() method of
the PreparedStatement object, so...

pstmt.setInt(1, regid);
pstmt.setString(2, name);
pstmt.setString(3, email);
pstmt.setString(4, mobile);

pstmt.executeUpdate(); //add this line

Please add the line number when you post stack trace again.

You were right Lin, I'm getting a ClassNotFoundException...Look at the stack trace below : @ line no 29 in the RegServlet.java

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1387)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1233)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Unknown Source)
        at com.dbentry.servlet.RegServlet.init(RegServlet.java:39)
        at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.
java:1172)
        at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.jav
a:808)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:129)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:286)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:845)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ss(Http11Protocol.java:583)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:44
7)
        at java.lang.Thread.run(Unknown Source)

What could be the problem and what do I need to do to get this work? Kindly suggest....And Thanks for reminding me about the executeUpdate statement....

Originally posted by Swapna Gouri Kalanidhi:
What could be the problem and what do I need to do to get this work?

hi you need to put mysql driver jar into your tomcat common/lib folder. if you are not having click here to download

Hope this helps

hi swapna,

put printing stack trace code here. You will get exact idea (root cause of
the problem). printing just a message like "insert failed" wont help you
much.

Thanks a bunch SeethaRaman! My code is working now...!

And Thanks to others too who have helped me fix this problem...!

But SeethaRaman, I would like to know how exactly it worked? I mean, when I did not place the mysql driver in Tomcat lib folder, why did I get NPE? What's the connection between both? Can you explain me in brief?

Originally posted by Swapna Gouri Kalanidhi:
I would like to know how exactly it worked?

so that tomcat can find your mysql jar , your application can communicate with your DataBase .for exact detail you can google it

I mean, when I did not place the mysql driver in Tomcat lib folder, why did I get NPE?

you wont get NullPointerException ,instead you get ClassNotFoundException . your code may throw NullPointerException due to operation on null connection .

What's the connection between both? Can you explain me in brief?

please goto tomcat/webapp/tomcate-doc folder in that read jndi-resources-howto.html document

Originally posted by Swapna Gouri Kalanidhi:
Thanks a bunch SeethaRaman! My code is working now...!

You "try", You "catch" and "finally" You WIN !!!

you are welcome