Change password for user

[Irfan Zubair]

Hi,
I get the following error for change password page.

StandardWrapperValve[password]: PWC1406: Servlet.service() for servlet password threw exception
java.lang.NullPointerException
at view.password.processRequest(password.java:78)
at view.password.doGet(password.java:112)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:718)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:411)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:317)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:198)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:198)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:288)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:271)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:202)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:632)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:577)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:206)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:632)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:577)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:571)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1080)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:150)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:632)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:577)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:571)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1080)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:272)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:637)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:568)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:813)
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.connector.grizzly.TaskBase.run(TaskBase.java:265)
at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)

password

package view;

import java.io.*;
import java.net.*;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.sql.DataSource;

/**
 *
 * @author sony
 */
public class password extends HttpServlet {
   
    /** 
    * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
    * @param request servlet request
    * @param response servlet response
    */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        List errorMsg=new LinkedList();
         errorMsg.clear();
        errorMsg=(List)request.getAttribute("errorMsg");
        String opassword=request.getParameter("opassword");
        String npassword=request.getParameter("npassword");
        String cpassword=request.getParameter("cpassword");
        if(opassword==null)
                opassword="";
        if(npassword==null)
                npassword="";
        if(cpassword==null)
                cpassword="";
          
        try 
        {
                    
                /*     TODO output your page here*/
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Change Password</title>");  
            out.println("</head>");
            out.println("<body>");
            out.println("<h1> Modify Password</h1>");
            out.println("<form method=\"POST\" action=\"pwdvalidate.do\">");
            out.println("<center>");
            out.println("<table border=\"0\" cellspacing=\"5\" cellpadding=\"5\">");
            out.println(" <tr>");
            out.println("<td>Old Password</td>");
            out.println(" <td><input type=\"password\" name=\"opassword\" size=\"30\"></td>");
            out.println("</tr>");
            out.println("<tr>");
            out.println("<td>New Password</td>");
            out.println("<td><input type=\"password\" name=\"npassword\" size=\"30\"></td>");
            out.println("</tr>");
            out.println("<tr>");
            out.println("<td>Confirm Password</td>");
            out.println("<td><input type=\"password\" name=\"cpassword\" size=\"30\"></td>");
            out.println("</tr>");
            if(!errorMsg.isEmpty())
            {
                out.println("<tr><td colspan=\"2\">");
                out.println("<font color=\"red\"");
                out.println("<p>");
                Iterator items=errorMsg.iterator();
                while(items.hasNext()){
                    out.println(items.next());
                }
                out.println("</p>");
                out.println("</font>");
                out.println("</td></tr>");
            }
            out.println("<tr>");
            out.println("<td colspan=\"2\"><input type=\"submit\" value=\"Update Password\"></td>");
            out.println("</tr>");
            out.println("</table>");
            out.println("</center>");
            out.println("</form>");
            out.println("</body>");
            out.println("</html>");
        
        } finally { 
            out.close();
        }
    } 
 // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
    * Handles the HTTP <code>GET</code> method.
    * @param request servlet request
    * @param response servlet response
    */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
        } 
        
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
    * Handles the HTTP <code>POST</code> method.
    * @param request servlet request
    * @param response servlet response
    */
   

   
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
        } 
        

    /** 
    * Returns a short description of the servlet.
    */
    public String getServletInfo() {
        return "Short description";
    }

    private DataSource getPassword() throws NamingException {
        Context c = new InitialContext();
        return (DataSource) c.lookup("java:comp/env/Password");
    }
    // </editor-fold>
}

pwdval.do

package Controller;

import java.io.*;
import java.net.*;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.LinkedList;
import java.util.List;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.sql.DataSource;

/**
 *
 * @author sony
 */
public class pwdvalidate extends HttpServlet {
   
    /** 
    * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
    * @param request servlet request
    * @param response servlet response
    */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        List errorMsg=new LinkedList();
        boolean flag=false;
       
        HttpSession session=request.getSession(true);
        try 
        {
            /* TODO output your page here*/
            String opassword=request.getParameter("opassword").trim();
            String npassword=request.getParameter("npassword").trim();
            String cpassword=request.getParameter("cpassword").trim();
            String currentPassword=new String();
            String username;
            username=(String) session.getAttribute("username");
            DataSource ds=getPwdValidate();
            Connection con=ds.getConnection();
            Statement st=con.createStatement();
            String sql="select password from logintablefl where username=\""+username+"\"";
            ResultSet rs=st.executeQuery(sql);
            System.out.println(sql);
            while(rs.next())
            {
                  currentPassword=rs.getString("password");
                  if(opassword.equals(currentPassword))
                  {
                         System.out.println(opassword);
                         flag=true;
                  }
                  if(npassword.equals(cpassword))
                  {
                      errorMsg.add("Updated");
                      out.println("Password update successfully");
                      session.setAttribute("username", username);
                      RequestDispatcher view = request.getRequestDispatcher("/faculty.view");
                      view.forward(request, response);
                      return;
                  }
             }
             if(opassword.isEmpty()&&npassword.isEmpty()&&cpassword.isEmpty())
             {
                     errorMsg.add("Please Enter All Fields");
             }
             else if(opassword.isEmpty())
             {
                     errorMsg.add("Please Enter Old Password.");
             }else if(npassword.isEmpty())
             {
                     errorMsg.add("Please Enter New Password.");
             }else if(cpassword.isEmpty())
             {
                     errorMsg.add("Please Enter Retype Password.");
             }
            request.setAttribute("errorMsg", errorMsg);
            if(!errorMsg.isEmpty())
            {
                RequestDispatcher view=request.getRequestDispatcher("password.view");
                view.forward(request, response);
                return;
            }
                 
          /*  out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet pwdvalidate</title>");  
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet pwdvalidate at " + request.getContextPath () + "</h1>");
            out.println("</body>");
            out.println("</html>");*/
            
      } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (NamingException ex) {
            ex.printStackTrace();
        } finally { 
            out.close();
        }
    } 

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
    * Handles the HTTP <code>GET</code> method.
    * @param request servlet request
    * @param response servlet response
    */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    } 

    /** 
    * Handles the HTTP <code>POST</code> method.
    * @param request servlet request
    * @param response servlet response
    */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /** 
    * Returns a short description of the servlet.
    */
    public String getServletInfo() {
        return "Short description";
    }

    private DataSource getPwdValidate() throws NamingException {
        Context c = new InitialContext();
        return (DataSource) c.lookup("java:comp/env/PwdValidate");
    }
    // </editor-fold>
}

[Bear Bibeault]

Here's the important part:

ava.lang.NullPointerException
at view.password.processRequest(password.java:78)

What does it tell you?

[Irfan Zubair]

Hi Bear Bibeault,
object which is null is being accessed. I don't know what is the mistake in the code?

[Jaikiran Pai]

Irfan Zubair wrote:
object which is null is being accessed. I don't know what is the mistake in the code?

It's simple - Find out what line number 78 of view.password class is and then look at that code to see which object is possibly null. Then find out why it's null and if it is a valid case for it to be null (in which case, you will need a null check there).

[Irfan Zubair]

Hi Jaikiran Pai,
The error found on if(!errorMsg.isEmpty()) in password.view
I tried to find why NullPointerException is raised, but I couldn't find it.

[Jaikiran Pai]

Irfan Zubair wrote:
The error found on if(!errorMsg.isEmpty()) in password.view
I tried to find why NullPointerException is raised, but I couldn't find it.

Here's an hint - What are the object(s) that are being accessed on that if(!errorMsg.isEmpty()) line?

[Irfan Zubair]

 Iterator items=errorMsg.iterator();  
                while(items.hasNext()){  
                    out.println(items.next());  
                }  

[Irfan Zubair]

I am struck with NullPointerException.

[Palak Mathur]

Irfan Zubair wrote:

 Iterator items=errorMsg.iterator();  
                while(items.hasNext()){  
                    out.println(items.next());  
                }  

If line 78 is if(!errorMsg.empty()), then the object being accessed is errorMsg. Check if errorMsg is a null.

[Irfan Zubair]

Hi Palak Mathur,
I am aware that errorMsg is somewhere null. I couldn't find. request.serAttribute("errorMsg",errorMsg) is set in pwd validate and request.getAttribute("errorMsg",errorMsg); is retrived in password.view. I don't know what has to be done futher.

[Ulf Dittmer]

Irfan Zubair wrote:I couldn't find. ... I don't know what has to be done futher.

That's easy: do some debugging. If you don't have, or are not familiar with, an actual debugger like JSwat or something built into your IDE, you can put a "System.out.println(errorMsg)" statement before every single usage of "errorMsg". That way you can see in your log files what value it has at which point. You'll also want to customize each println statement so that you can tell them apart, like System.out.println("1 "+errorMsg), System.out.println("2 "+errorMsg) etc.