null pointer exception in struts2

[Pradeep Adibatla]

We all know that the variable name in Action class should be name of the html tag...

I have something like this

<div id="Add" title="foradding" style="display:none;" >
             
                      <table align="left" >
                      <form>
                          <br/>
                          <tr>
                               <td>Conceptname:</td>
                               <td><input  type="text" id="conName" name="conceptName"></td>
                               <td> </td>
                          </tr>
             
                          <tr>
                               <td>Attributename:</td>
                               <td><input type="text" id="atrName"  name="attributeName"></td>
                               <td> </td>
                          </tr>
                           
                          <tr>
                               <td>Datatypename:</td>
                              <td>
                                  <select id="dtName" name='addDTList'>
                                       <option>String</option>
                                       <option>Integer</option>
                                       <option>Real</option>
                                       <option>Boolean</option>
                                       <option>Date</option>
                                   </select>
                                                         
                                </td>  
                                <td> </td>
                          </tr>    
                          <tr>
                              <td><input type="submit" value="Ok" name="addVocOk" onclick="addRow('vocab','Add')"/></td>   <!--addRow('vocab')-->
                              <td><input type="button" value="Cancel" onclick="hideAddVoc('Add')"/></td>
                          </tr>
                      </form>
                      </table>
                  
         </div>

The variable names in action class:
private String conceptName;
private String attributeName;
private String addDTList;

I also have get,set methods for these...

On click on submit

When I print the above values its only printing addDTList while the other 2 are null,,,why is that so??

[Ankit Garg]

Can you show us the code of your action and what you are doing in the addRow('vocab','Add') method...

[Pradeep Adibatla]

code for addRow() method

  

function addRow(vocab,buttonType)
{
    alert(" ---->  in addRow ");

       frm=document.forms[0]


    
    //content,morecontent,mostcontent,
        document.getElementById(buttonType).style.visibility = 'hidden';

         if (!document.getElementsByTagName) return;
         tabBody=document.getElementById(vocab).getElementsByTagName("TBODY").item(0);
         alert(tabBody);

         row=document.createElement("TR");

         vocabBody=row;

 
         cell1 = document.createElement("TD");
         cell2 = document.createElement("TD");
         cell3 = document.createElement("TD");
         cell4 = document.createElement("TD");

         alert("The ct value is :--->"+ct);
        
         cell1.innerHTML=ct;

         alert("cell1 value is :-->"+cell1.innerHTML);

   //      alert(document.getElementById('conName'));
         textnode2=document.getElementById('conName');
         textnode3=document.getElementById('atrName');
         textnode4=document.getElementById('dtName');

   //      alert("The con is :-->"+textnode2.value);
   //      alert("The atr is :-->"+textnode3.value);
   //      alert("The dtp is :-->"+textnode4.value);
   

         cell2.innerHTML=textnode2.value;
         cell3.innerHTML=textnode3.value;
         cell4.innerHTML=textnode4.value;


    //     alert("The val in cell2 is :-->"+cell2.innerHTML);
    //     alert("The val in cell3 is :-->"+cell3.innerHTML);
    //     alert("The val in cell4 is :-->"+cell4.innerHTML);


         row.appendChild(cell1);
         row.appendChild(cell2);
         row.appendChild(cell3);
         row.appendChild(cell4);
         tabBody.appendChild(row);

      //   vocabBody=tabBody;

         ++ct;


        alert("Now ct is :-->"+ct)
   //     alert("row.onmouseover is :---"+row.onmouseover);

        
          frm.addVocabulary.disabled = false;
          frm.modifyVocabulary.disabled = false;
          frm.deleteVocabulary.disabled = false;
          frm.saveVocabulary.disabled = false;

          frm.conceptName.value='';
          frm.attributeName.value='';


}

var a=1;
function Trace(vocab)
{
//alert("---- I am in Trace !!! ");

   //     alert("vocaBody is :-->"+vocabBody);


        if(vocab=='over')
        {
          //  alert("vocab == vocab !!!")
   
      //        alert("its mouseover ---");
              ChangeColor(vocabBody, true);
        }
        if(vocab=='click')
        {
       //       alert("its mouseonclick")
              ChangeColor(vocabBody, true);
        }
         if(vocab=='click')
        {
       //       alert("its mouseonclick")
              a=2;
              ChangeColor(vocabBody, true);
        }
        if(vocab=='out' && a!=2)
        {
            
      //        alert("its mouseout") ;
              ChangeColor(vocabBody, false);
        }
       
}


function ChangeColor(tableRow, highLight)
{
  //  alert(" ---> in ChangeColor function  -- ");
    if (highLight)
    {
  //    alert("its highlight");
      tableRow.style.backgroundColor = '#dcfac9';
    }
    else
    {
  //    alert("in else,no lite !!!");
      tableRow.style.backgroundColor = 'white';
    }
  }
  

and here is the action class...

  

public class VocabularyAction extends ActionSupport
{
  private String gotoRuleset;
  private String conceptName;
  private String attributeName;
  private String  saveVocabulary;
  private String addDTList;
  private String addVocOk;
   private String vocchk2;
  private ArrayList vocabularyList;
  public VocabularyObjectToDBPersistence vocabularyObjectToDBPersistence;
  public Vocabulary vocabulary;
  public Concept concept;
  public Attribute attribute;

    public String getSaveVocabulary()
    {
        System.out.println("in getSaveVoc !!!");
        return saveVocabulary;
    }

    public void setSaveVocabulary(String saveVocabulary)
    {
        System.out.println("in setVocabulary !!!");
        this.saveVocabulary = saveVocabulary;
    }
  

    public String getAddVocOk()
    {
        System.out.println("--- In getAdVocOK ---");
        return addVocOk;
    }

    public void setAddVocOk(String addVocOk) {
        this.addVocOk = addVocOk;
    }
 


    public ArrayList getVocabularyList() {
        return vocabularyList;
    }

    public void setVocabularyList(ArrayList vocabularyList) {
        this.vocabularyList = vocabularyList;
    }

    public String getVocchk2() {
        return vocchk2;
    }

    public void setVocchk2(String vocchk2) {
        this.vocchk2 = vocchk2;
    }

   

    public String getAddDTList() {
        return addDTList;
    }

    public void setAddDTList(String addDTList) {
        this.addDTList = addDTList;
    }

    

//    @RequiredFieldValidator(type = ValidatorType.SIMPLE,
//           fieldName = "conceptName",
//           message="conceptName Field is Required.")
    public String getConceptName() 
    {
        System.out.println(" ---- in getConceptName");
        return conceptName;
    }

    public void setConceptName(String conceptName)
    {
        System.out.println(" ---- in setConceptName");
        this.conceptName = conceptName;
    }

//     @RequiredFieldValidator(type = ValidatorType.SIMPLE,
//           fieldName = "attributeName",
//           message="attributeName Field is Required.")
    public String getAttributeName() 
    {
        System.out.println(" ---- in getAttributeName");
        return attributeName;
    }

    public void setAttributeName(String attributeName) 
    {
        System.out.println(" ---- in setAttributeName");

        this.attributeName = attributeName;
    }

   
    public String getGotoRuleset() {
        return gotoRuleset;
    }

    public void setGotoRuleset(String gotoRuleset) {
        this.gotoRuleset = gotoRuleset;
    }


   String target;

    @Override
    public String execute() throws Exception
    {

          vocabularyList=new ArrayList();

          System.out.println("Inside Vocabulary Action Class");

        // -----------  for adding to db/xml  --------------

          System.out.println("The addVocOk is :-->"+addVocOk);
          System.out.println("saveVocabulary-->"+saveVocabulary);
          System.out.println("gotoRuleset-->"+gotoRuleset);

         
          if(addVocOk!=null)
          {
              
              System.out.println(" ---  it's in addVocabulary !!!");
                           
              try
              {
                  System.out.println("The vals are :--->"+conceptName+","+attributeName+","+addDTList);
                  attribute.setAttributeName(attributeName);
                  attribute.setDataType(addDTList);
                  concept.setConceptName(conceptName);

                  vocabulary.addConcept(conceptName, attributeName, addDTList);
                  
                  vocabularyObjectToDBPersistence.setDataToDB(concept, attribute);
                  target="success1";
              }
              catch(DuplicateException de)
              {
                  System.out.println("The de is :-->"+de);
                //  target="failure";
              }
              catch(NullPointerException npe)
              {
                  System.out.println("The npe is :--"+npe);
                //  target="failure";
              }
              catch (Exception e)
               {
                    System.err.println("msg is :-->" + e.getMessage());
                 //   target="failure";
               }

               return target;
            }

          else if(gotoRuleset!=null)
          {
           if (gotoRuleset.equalsIgnoreCase("RuleSets"))
           {
             System.out.println(" ---> its in voc");
             target= "success2";

           }
           else
           {
            target= "failure";
           }
        }

      System.out.println("voc target is :-->"+target);

      return target;

    }


}

 

The output on button click is as follows...

--------------------------------------------------------
Inside Vocabulary Action Class
The addVocOk is :-->Ok
saveVocabulary-->null
gotoRuleset-->null
--- it's in addVocabulary !!!
The vals are :--->,,Integer
The npe is :--java.lang.NullPointerException


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

[Ankit Garg]

I'm clueless what you are trying to do with that method in JS as the dynamic row that you create will be of no use as the page will be posted back. And what's the use of these two lines

 frm.conceptName.value='';  
 frm.attributeName.value='';

[Ankit Garg]

Also in your action, is the field public Attribute attribute; initialized anywhere?? The line The vals are :--->,,Integer in your output shows that the values of conceptName and attributeName are empty and not null...

[Pradeep Adibatla]

Hi Ankit,

I want to add rows dynamically and also allow selection of rows on mouse click (delete,modify both UI and DB)...that's what i am trying to do...

yes the page is being posted back and being a tyro am struggling how to avoid it.

I guess I should create objects of concept and attribute there!

Those 2 lines are incorrect...removed!

Any other suggestions and solutions from your side would be of great help...

[Ankit Garg]

If you want to add dynamically on the server without the page posting back, then you'll have to use an AJAX request. To stop postback of the page, either make the OK button a normal button instead of submit button or return false from the addRow method...

[Pradeep Adibatla]

But If I make OK or normal button, it cuts the interaction with action class and nothing happens...only submit would allow interaction with Action class,itsn't it?correct me I f I am wrong.

Also,congrats on that scjp score...I am writing SCJP 6.0 on NOV 8th as it was a bit haste due to some reasons and I have zero preparation...Do you think I can make the cut? I will be starting my preparation today ans some inputs,papers etc would be of great help.Thanks!

[David Newton]

That's why the previous comment said to use Ajax.

[Ankit Garg]

Pradeep Adibatla wrote:I am writing SCJP 6.0 on NOV 8th as it was a bit haste due to some reasons and I have zero preparation...Do you think I can make the cut? I will be starting my preparation today ans some inputs,papers etc would be of great help.Thanks!

So you are going to rely on 9-10 days of preparation?? That's not good. The SCJP exam is not that easy to crack. Why don't you postpone the exam a bit. Also for further discussion on this, start a new thread in the SCJP Forum...

[Pradeep Adibatla]

In my above mentioned JavaScript I want to add rows and do mouseover and out for all the rows I add and then select any row but alas i could do that only with the recent row added...what should be the change? help...