Forum:

Null Pointer Execption error when running application

Ranch Hand

Posts: 88

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi folks...

I am trying to display content from a table in a database. I am using datasource to do this. When I run the application I
am getting the following error:

HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.NullPointerException
root cause

java.lang.NullPointerException

-----------------------------------------------------------------------------------

The 3 files involed are as follows:

us_states.jsp:

JDBCSelectServlet.java:

package net.ensode.glassfishbook.jdbcselect;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

public class JDBCSelectServlet extends HttpServlet
{
  @Override
  protected void doGet(HttpServletRequest request,
                       HttpServletResponse response) throws
                       ServletException, IOException
  {
    String sql = "select us_state_nm, " +
        "us_state_cd from us_states order by us_state_nm";
    ArrayList<UsStateBean> stateList =
        new ArrayList<UsStateBean>();

try
    {
      InitialContext initialContext = new InitialContext();
      DataSource dataSource = (DataSource) initialContext
          .lookup("jdbc/__CustomerDB1Pool");
      Connection connection = dataSource.getConnection();
      PreparedStatement preparedStatement =
          connection.prepareStatement(sql);
      ResultSet resultSet = preparedStatement.executeQuery();
      while (resultSet.next())
      {
        stateList.add(new
            UsStateBean(resultSet.getString("us_state_nm"),
            resultSet.getString("us_state_cd")));
      }

resultSet.close();
      preparedStatement.close();
      connection.close();

request.setAttribute("stateList", stateList);

request.getRequestDispatcher("us_states.jsp").
          forward(request, response);
    }
    catch (NamingException namingException)
    {
      namingException.printStackTrace();
    }
    catch (SQLException sqlException)
    {
      sqlException.printStackTrace();
    }
  }
}

UsStateBean.java:

I am not sure what is wrong. Can anyone point out the problem to me? Thanks.

Bear Bibeault

Sheriff

Posts: 67754

173

I like...

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Where is the stack trace?

[Asking smart questions] [About Bear] [Books by Bear]

HTML 5 (verified skill)
Skill verified by Jeanne Boyarsky

CSS 3 (verified skill)
Skill verified by Jeanne Boyarsky

JavaScript (verified skill)
Skill verified by Jeanne Boyarsky

Varnam Aayiram

Ranch Hand

Posts: 88

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi..

Thanks for the reply, the stack trace is as follows:

StandardWrapperValve[jsp]: PWC1406: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
        at org.apache.jsp.us_005fstates_jsp._jspService(us_005fstates_jsp.java from :75)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:389)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:486)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:380)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:427)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:315)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:287)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:218)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:222)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:166)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:288)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:647)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:579)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:831)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214)
        at com.sun.enterprise.web.portunif.PortUnificationPipeline$PUTask.doTask(PortUnificationPipeline.java:380)
        at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265)
        at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)

Bear Bibeault

Sheriff

Posts: 67754

173

I like...

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

OK, so at least we now know that it's coming from the JSP.

Most likely reason is that either of stateList or state ends up as null.

By the way, why are you still using outdated scriptlets and scriptlet expressions? You've already separated the logic form the JSP, using the JSTL and EL should be a snap.

[Asking smart questions] [About Bear] [Books by Bear]

Varnam Aayiram

Ranch Hand

Posts: 88

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Bear Bibeault wrote:OK, so at least we now know that it's coming from the JSP.

Most likely reason is that either of stateList or state ends up as null.

By the way, why are you still using outdated scriptlets and scriptlet expressions? You've already separated the logic form the JSP, using the JSTL and EL should be a snap.

Hi there Bear Bibeault ,

Appreciate the reply. I will look into the possibility that you have highlighted. I am also wondering if the setting up of the datasource in my glassfish server could also be a possible cause, but I am able to do a ping sucessfully after setting up the datasource...

Actually these codes are something that I got from a book. I am trying them out on my machine to better understand them, so that I can implement something similar on an application I am developing. Yes, I have heard of JSTL and EL and how they can make life easier. Once I settle this 'nullpointer' issue, I will replace the scriplets with JSTL/EL. Thanks once again.

Varnam Aayiram

Ranch Hand

Posts: 88

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi...

I am just curious, the file us_states.jsp does not explictly 'call' any particular servlet, unlike a form submission where a servlet is mentioned explicitly. So how does the server know which servlet to call/invoke?

Bear Bibeault

Sheriff

Posts: 67754

173

I like...

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

I'm not sure what you mean by that. The verb "call" is completely ambiguous in this context.

[Asking smart questions] [About Bear] [Books by Bear]

Mark E Hansen

Ranch Hand

Posts: 650

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Varnam Aayiram wrote:Hi...

I am just curious, the file us_states.jsp does not explictly 'call' any particular servlet, unlike a form submission where a servlet is mentioned explicitly. So how does the server know which servlet to call/invoke?

It looks like your JSP page is going to display a list of states, but not otherwise do anything at all. Is this what was intended?
Did you want the user to select a state, then click on a Submit button or something? That appears to not be there.

Shinelin Samuel

Ranch Hand

Posts: 55

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi,

Like you mentioned you are setting up the environment for this project, double check if you the table us_states has records, loaded in it.

Probably that could the reason for your issue.

Regards,
Shinelin

Shailendra Mishra

Greenhorn

Posts: 4

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi,

WHILE YOU ARE PUTTING THE VALUE IN ARRAY LIST EITHER resultset is nothing return or the way you Are ptting need to watch it again.

Jinglong Wang

Greenhorn

Posts: 12

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

hi,
i need know how do you run this.
direct run the jsp or request a servlet?

if you direct run the jsp,the nullpoint is right.
the nullpointException throw out in line 25.
because the stateList is null.

Varnam Aayiram

Ranch Hand

Posts: 88

posted 15 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Hi Guys..

Thanks for the replies, I appreciate it. Yes as some of you had pointed out, the mistake was in running from the jsp direct. I have rectified the mistake. Thanks everyone.

Did you see how Paul cut 87% off of his electric heat bill with 82 watts of micro heaters?