Can you help me with these exceptions??

Question

Hi guys,
from sunday i try to eliminate these exceptions from my jsf application and i've lost any confidence in my possibility to realize it.....
It's surely a simple problem but i'm a newbie of jsf and java.
These are the exadel msg
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: #{MyBean.retrieveblob}: javax.faces.el.EvaluationException: java.lang.NullPointerException
     javax.faces.webapp.FacesServlet.service(FacesServlet.java:209)
     org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:144)
root cause
javax.faces.FacesException: #{MyBean.retrieveblob}: javax.faces.el.EvaluationException: java.lang.NullPointerException
     com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:78)
     javax.faces.component.UICommand.broadcast(UICommand.java:312)
     javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:267)
     javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:381)
     com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:75)
     com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
     com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:90)
     javax.faces.webapp.FacesServlet.service(FacesServlet.java:197)
     org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:144)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
ant these are the files
MyBean.java
package giu;
import org.apache.myfaces.custom.fileupload.UploadedFile;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import java.util.Vector;
public class MyBean {
     private UploadedFile myFile;
     private String geneid=null;
    private int row=0;
    private int numberOfNumericColumns=0;
    private int col=0;
    String[]intest=null;
    private ArrayList rows = new ArrayList();
    Head h;
    byte middlerow=' ';
    byte endrow=';';
    byte[] data=null;
    Vector temp=new Vector(100000);
    String g=null;
    Riga r;
    Double val[];
    private String[] arraylinee;
    public boolean insRighe(Riga nuovo){
           return rows.add(nuovo);
    public List stampaRows(){
         return rows;}
    public Head stampaHead(){
         return h;}
    public byte[] getdata(){
         return data;
    public UploadedFile getMyFile() {
        return myFile;
    public void setMyFile(UploadedFile myFile) {
        this.myFile = myFile;
    public int getcol(){
         return col;
    public void setcol(int col){
         this.col=col;
    public int getrow(){
         return row;
    public void setrow(int row){
         this.row=row;
    public String[] getarraylinee(){
         return arraylinee;
    public void setarraylinee(String[] arraylinee){
         this.arraylinee=arraylinee;
public String retrieveblob(){
          Database2 db = new Database2("nomeDB","root","shevagol");     
          try
          Connection dbo=db.getConnection();
          System.out.println("eccezione buona2");
               System.out.println("eccezione buona2,5");
               Statement st = dbo.createStatement();
               System.out.println("eccezione buona3");
               ResultSet rs;
               rs = st.executeQuery("SELECT Data FROM tbl WHERE Nome='16'");
               rs.first();
               Blob blob = rs.getBlob("Data");
               byte[] read = blob.getBytes(1, (int) blob.length());
               st.close();
               String lettura=new String(read);
               String[] arraylinee=lettura.split(";");
               /*for (int i = 0; i < arraylinee.length; i++) {
                 System.out.println(arraylinee);
          catch(SQLException e)
               System.out.println("Si � verificato il seguente errore: " + e.getMessage());
               e.printStackTrace();
          return "retrOk";
This is my result.jsp page
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
<%@ page import="giu.MyBean" %>
<%-- Instantiate class --%>
<jsp:useBean id="myBean" class="giu.MyBean" scope="request"/>
<html>
     <head>
          <title></title>
     </head>
     <body>
          <f:view>
               <c:forEach items="${myBean.arraylinee}" var="linea" >
<tr>
<td>
<c:out value="${linea}" />
</td>
</tr>
</c:forEach>
          </f:view>
     </body>     
</html>
and these are web.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
     <context-param>
          <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
          <param-value>client</param-value>
     </context-param>
     <filter>
          <filter-name>ExtensionsFilter</filter-name>
          <filter-class>org.apache.myfaces.component.html.util.ExtensionsFilter</filter-class>
          <init-param>
               <param-name>uploadMaxFileSize</param-name>
               <param-value>100m</param-value>
          </init-param>
          <init-param>
               <param-name>uploadThresholdSize</param-name>
               <param-value>100k</param-value>
          </init-param>
     </filter>
     <filter-mapping>
          <filter-name>ExtensionsFilter</filter-name>
          <servlet-name>FacesServlet</servlet-name>
     </filter-mapping>
     <servlet>
          <servlet-name>FacesServlet</servlet-name>
          <servlet-class>
          javax.faces.webapp.FacesServlet</servlet-class>
          <load-on-startup>1</load-on-startup>
     </servlet>
     <servlet-mapping>
          <servlet-name>FacesServlet</servlet-name>
          <url-pattern>/faces/*</url-pattern>
     </servlet-mapping>
     <servlet-mapping>
          <servlet-name>FacesServlet</servlet-name>
          <url-pattern>*.faces</url-pattern>
     </servlet-mapping>
     <welcome-file-list>
          <welcome-file>index.jsp</welcome-file>
     </welcome-file-list>
</web-app>
and faces-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN"
                              "http://java.sun.com/dtd/web-facesconfig_1_1.dtd">
<faces-config>
<managed-bean>
  <managed-bean-name>MyBean</managed-bean-name>
  <managed-bean-class>giu.MyBean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
</managed-bean>
<navigation-rule>
  <from-view-id>/pages/MyForm.jsp</from-view-id>
  <navigation-case>
   <from-outcome>success</from-outcome>
   <to-view-id>/pages/MyResult.jsp</to-view-id>
  </navigation-case>
</navigation-rule>
<navigation-rule>
  <from-view-id>/pages/Login.jsp</from-view-id>
  <navigation-case>
   <from-outcome>Ok</from-outcome>
   <to-view-id>/pages/Menu.jsp</to-view-id>
  </navigation-case>
</navigation-rule>
<navigation-rule>
  <from-view-id>/pages/Menu.jsp</from-view-id>
  <navigation-case>
   <from-outcome>upload</from-outcome>
   <to-view-id>/pages/MyForm.jsp</to-view-id>
  </navigation-case>
  <navigation-case>
   <from-outcome>admin</from-outcome>
   <to-view-id>/pages/UserForm.jsp</to-view-id>
  </navigation-case>
  <navigation-case>
   <from-outcome>view</from-outcome>
   <to-view-id>/pages/ViewForm.jsp</to-view-id>
  </navigation-case>
  <navigation-case>
   <from-outcome>register</from-outcome>
   <to-view-id>/pages/Register.jsp</to-view-id>
  </navigation-case>
</navigation-rule>
<navigation-rule>
  <from-view-id>/pages/ViewForm.jsp</from-view-id>
  <navigation-case>
   <from-outcome>Result</from-outcome>
   <to-view-id>/pages/Result.jsp</to-view-id>
  </navigation-case>
</navigation-rule>
</faces-config>I hope someone can helps me...............
P.S.
Can someone says me a good program to debug my applications...?
I try with exadel but i find it bit intuitive....

Answer 1

I don't know JSF, but it appears you haven't included part of your application - the one causing the error with the line: #{MyBean.retrieveblob}
I would assume the error is that you instantiate the bean with the name "myBean" (<jsp:useBean id="myBean" class="giu.MyBean" scope="request"/>) then refer to it as "MyBean". Java is case sensitive.