Exception java.lang.NumberFormatException: null in servlets

Question

String Dept  = request.getParameter("dept");
int NumOfEmp = Integer.parseInt(request.getParameter("EmployeeNum"));

if(null != Dept && !Dept.isEmpty()){
       // add criteria for Name
      query += " AND DeptName = '"+ Dept + "'"; // prefer parametrized query
    }

    if(NumOfEmp > 0){

        // add criteria for Age
      query += " AND NumberOfEmployees = "+ NumOfEmp ;  // prefer parametrized query
    }

System.out.println("QUERY ......... " +  query);
pst = c.prepareStatement(query);

The query that gets formed looks just fine :

here is what I got:

select DeptName, NumberOfEmployees from Departments where 1 = 1 AND 

         NumberOfEmployees = 50

The query looks good to me but just after printing the query, noting is printed on console. Then If I explicitly call the url, it gives an exception that says:

 Exception java.lang.NumberFormatException: null

Data string that I passed from ajax:

var dataString ={ "EmployeeNum" : "50"};

How I can I resolve this ?What seems to be the issue here ?

Edit : Here is the complete code:

package com.Charts;

/**
 * Servlet implementation class DBChart
 */
@WebServlet("/db")
public class DBChart extends HttpServlet
{
Connection c = null;
//Statement st = null;
ResultSet rs = null;
String query = null;
JSONObject obj = null;
JSONObject resobj =null;
PreparedStatement pst = null;
//DatabaseMetaData dbmd = null;
String dbURL="jdbc:sqlserver://localhost:1433; databaseName = EMPLOYEE";
String user = "sa";
String password = "minisiminoni";
public  void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{
try
{
List<JSONObject> Details = new LinkedList<JSONObject>();
PrintWriter out = response.getWriter();
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
c = DriverManager.getConnection(dbURL, user, password);
query = "select DeptName, NumberOfEmployees from Departments where 1 = 1";
String Dept = "";
try
{
Dept  = request.getParameter("dept");
}
catch(Exception e)
{
System.out.println("request param dept " + e);
}
String EmployeeNum= "";
try
{
 EmployeeNum = request.getParameter("EmployeeNum");
}
catch(Exception e)
{
System.out.println("error in get param" + e );
}
int NumOfEmp;
try {
    NumOfEmp = Integer.parseInt(EmployeeNum);
} catch(NumberFormatException e){
    StringBuilder sb = new StringBuilder();
    sb.append("Error parsing this EployeeNum: ");
    sb.append(EmployeeNum);
    e.printStackTrace();
    throw new RuntimeException(sb.toString());
}

if (Dept != null && !Dept.isEmpty()) {
      // add criteria for Name
      query += " AND DeptName = '"+ Dept + "'"; // prefer parametrized query
    }
    if (NumOfEmp > 0) {
     // add criteria for Age
      query += " AND NumberOfEmployees = "+ NumOfEmp ;  // prefer parametrized query
    }
System.out.println("QUERY ......... " +  query);
pst = c.prepareStatement(query);
resobj = new JSONObject();
while(rs.next())
{
String DeptName = rs.getString(1);
System.out.println("name " + DeptName);
int NumberOfEmployees = rs.getInt(2);
System.out.println("num " + NumberOfEmployees );
obj = new JSONObject();
obj.put("DeptName", DeptName);
obj.put( "NumberOfEmployees",NumberOfEmployees );
Details.add(obj);
}
resobj.put("Details", Details);
out.write(resobj.toString());

}
catch(Exception e)
{
System.out.println("Exception " + e);  //only this is where exception is caught
}
}
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     doGet(request, response);
  }
}

Console :

INFO: QUERY ......... select DeptName, NumberOfEmployees from Departments where 1 = 1 AND NumberOfEmployees = 50
2015-03-27T14:32:30.604+0530|SEVERE: SLF4J: The requested version 1.6 by your slf4j binding is not compatible with [1.5.5, 1.5.6]
2015-03-27T14:32:30.604+0530|SEVERE: SLF4J: See http://www.slf4j.org/codes.html#version_mismatch for further details.

After then nothing :

Then if I explicitly go to servlet URL , I get this :

2015-03-27T14:33:58.670+0530|INFO: Exception java.lang.NumberFormatException: null

Here is my ajax call:

<script type="text/javascript">
            var dataString ={ "EmployeeNum" : "50"};
            var queryObject="";
            var queryObjectLen="";
            console.log("loading");
            google.load('visualization', '1.0', {'packages':['corechart']});
google.setOnLoadCallback(function() {
    $.ajax({
        type : 'POST',
        data:  dataString,
        url : 'http://localhost:8080/Charts/db',
        success : function(data) {
        alert("success");
            queryObject = jQuery.parseJSON(data);            
            queryObjectLen = queryObject.Details.length;
            console.log("queryObj: "+queryObject+" Length: "+queryObjectLen);
            drawChart();
        },
        error : function(xhr, type) {

            alert('server error occoured')
        }
    }).done(function(msg) {
            alert("aa gya Response: " + msg);
        });
});

Post the entire Stack Trace !!! it will explain better exactly on which line you are getting this exception ! — Neeraj Jain, Mar 27 '15 at 08:41
Possible your Connection reference Variable `c` , might not be initialized yet !! — Neeraj Jain, Mar 27 '15 at 08:43
I am using GlassFish and there is nothing else in stacktrace. — Simran kaur, Mar 27 '15 at 08:43
@Simrankaur , then you might wrap up your code snippet in `try-Catch block` — Neeraj Jain, Mar 27 '15 at 08:44
@vijay: This is the only relevant piece of code. Besides,I am just passing parameters from ajax which seem to have been passed just fine/ — Simran kaur, Mar 27 '15 at 08:44
From what you have provided so far, the NFE can happen at the statement >> Integer.parseInt(request.getParameter("EmployeeNum")); request.getParameter("EmployeeNum") returning a non integer value — RahulArackal, Mar 27 '15 at 08:44
@Simrankaur, you did not provide query variable initialization part of code — vijay, Mar 27 '15 at 08:45
@iMmo: I just updated post with the data string.Also, it if it was happening there I would have my query printed on log just fine , isn't it ? — Simran kaur, Mar 27 '15 at 08:46
then try a Sysout of request.getParameter("EmployeeNum") and check if it alwys gives you a value which is convertable to Integer. — RahulArackal, Mar 27 '15 at 08:47
@Simrankaur , i think you can not directly parse JSON with request.getParameter(parameterName) !!! — Neeraj Jain, Mar 27 '15 at 08:49
Why was the question marked as duplicate when two cases are different and it clearly does not answer mine. — Simran kaur, Mar 27 '15 at 08:52
@NeerajJain: http://stackoverflow.com/questions/9293991/how-to-get-the-data-via-ajax-in-servlet See this link, it clearly states that what I am doing is just the right way to do it. — Simran kaur, Mar 27 '15 at 08:56
there is a difference between JSON Object and JSON String !!!! Hope you got what i wanted to explain , GSON will parse both too smoothly — Neeraj Jain, Mar 27 '15 at 08:57
@NeerajJain: No, I actually have not yet. If you see that example, they have JSON object via which parameters were passed to servlet. Do you mind explaining how do you see them any different ? — Simran kaur, Mar 27 '15 at 08:59
Pls provide the query building block and query execution in full. Put the entire block within try / catch block The prepareStatement(query); only throws SQLException. So thats not the case — RahulArackal, Mar 27 '15 at 08:59
I think try/catch & some basic debugging will be enough for this issue. — RahulArackal, Mar 27 '15 at 09:00
@iMmo: Please check the edit 1. I do not get anything printed after Query . and then If I explicitly use servlet url in browser, I get this exception.Please check the post update. — Simran kaur, Mar 27 '15 at 09:08
Hi, can you keep you code in try catch, and post exactly in which line u r getting the issue, by details of exception there is only one line where it can be throw, but your print of query suggest something else. — Techfist, Mar 27 '15 at 09:18
@Techfist: Could you please check the code now ? I have multiple try catch now and none of them seems to catch the exception. — Simran kaur, Mar 27 '15 at 09:24
@iMmo: This is where it gets data in JSON format .This is the same servlet url. — Simran kaur, Mar 27 '15 at 10:59
@Techfist: true condition to be able to make dynamic sql. ( so that I could havewhere clause there before appending more conditions) — Simran kaur, Mar 27 '15 at 11:00

score 1 · Answer 1 · answered Mar 27 '15 at 09:03

There are many corrections to your code

1st : SQL Query
Do you really need this 1 = 1 it smeels like SQL Injection.. so remove it

2nd Java Code
A. Always try{}catch(){} code blocks that can generate an exception;
B. Always print a comprehensive error message;
C. it is a must to use log4j for ex;

3rd Business rules
A. You must check if number of employees is as you expect it Great or Equal to Zero
B. Prevent your Code from SQL Injection

Try with this code

String Dept  = request.getParameter("dept");
String EmployeeNum = request.getParameter("EmployeeNum");
try {
    int NumOfEmp = Integer.parseInt(EmployeeNum);
} catch(NumberFormatException e){
    StringBuilder sb = new StringBuilder();
    sb.append("Error parsing this EployeeNum: ");
    sb.append(EmployeeNum);
    e.printStackTrace();
    throw new RuntimeException(sb.toString());
}

if (Dept != null && !Dept.isEmpty()) {
      // add criteria for Name
      query += " AND DeptName = '"+ Dept + "'"; // prefer parametrized query
    }
    if (NumOfEmp > 0) {
     // add criteria for Age
      query += " AND NumberOfEmployees = "+ NumOfEmp ;  // prefer parametrized query
    }
System.out.println("QUERY ......... " +  query);
pst = c.prepareStatement(query);

Hey, I tried this and I still have exactly the same behavior. I get exception when I explicitly call the url otherwise console prints untiil query is formed and then nothing at all. — Simran kaur, Mar 27 '15 at 09:12

Exception java.lang.NumberFormatException: null in servlets

1 Answers1