null pointer exception occuring in java servlet

Question

I am developing a comment forum that is people will comment and can see their comments after posting but i am getting null pointer exception in servlet.

index.jsp

<form action="Comment" method="post">

  <textarea style="resize: none;" cols="30" rows="3" id="myTextarea" name="myTextarea"></textarea>

</form>

Comment servlet

  try{
    String comment=request.getParameter("myTextarea");

       ArrayList al1=null;
        ArrayList emp_list =new ArrayList();
         al1.add(comment);       
         emp_list.add(al1);                 
         request.setAttribute("empList",emp_list);        
        String nextJSP = "/result.jsp";
       RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(nextJSP);
      dispatcher.forward(request,response);
    }       
    catch(Exception e){       
    out.println("exception"+e);//exception coming 

    }

sje397 · Accepted Answer · 2012-04-18 06:33:43Z

2

You al1 will be null when you try to add to it:

ArrayList al1=null;
ArrayList emp_list =new ArrayList();
al1.add(comment);

Try changing the first line to:

ArrayList al1 = new ArrayList();

This will result in forwarding an array list inside an array list to your next jsp page. It might be simpler to just do:

ArrayList emp_list =new ArrayList();
emp_list.add(comment);

...and remove the varialble al1 altogether.

answered Apr 18, 2012 at 6:33

sje397

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4 Comments

sujit Over a year ago

yes this solved the problem, i just need few help , how can i get this emp_list.add(comment) in result.jsp ? will i get multiple comments?

sje397 Over a year ago

Your call to setAttribute should make it a request parameter you can access in result.jsp. No, as it is you will get one comment inside an array in the parameter empList.

sujit Over a year ago

ya i am getting only one comment and it is getting replaced if i am entering a different comment, how can i get multiple comments? please help me little bit

sje397 Over a year ago

@sujit - A lot depends on the other parts of your code. Often, you would just write the comment to a database in this handler, and read a list from there for display inside your results page. Can you create another question with more explanation of the path the data takes?

tanyehzheng · Accepted Answer · 2012-04-18 06:32:56Z

1

Your al1 arraylist is instantiated to null! try

ArrayList<String> al1 = new ArrayList<String>();
al1.add(comment);

answered Apr 18, 2012 at 6:32

tanyehzheng

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2 Comments

sujit Over a year ago

i have added string comment to al1 by al1.add(comment)

tanyehzheng Over a year ago

when you call al1.add(comment), you're not adding the string to the an arraylist object, you're adding your "comment" to "null" because you instantiated al1 = null;

deepmoteria · Accepted Answer · 2012-04-18 07:13:44Z

0

Dude you are assigning the reference to a null. that is al1.add(), just assign it with the memory using new, it will solve your problem....... Enjoy........

answered Apr 18, 2012 at 7:13

deepmoteria

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