handling wrong data type entry through servlet

[shaz baluch]

Salaam All!
This servlet works well when I enter the correct data type in the required fields but with wrong entry and blank entry it only shows exception error. So how would I handle this through a message? how to code this?
thanks

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class InsertSTServlet extends HttpServlet
{
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
    {
		try
		{
			PrintWriter out = response.getWriter();


			Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
			Connection conn = DriverManager.getConnection("jdbc:odbc:colConn");
			PreparedStatement stmt = conn.prepareStatement("insert into StudentRecord values (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)");

			String sessionId = request.getParameter("sessionId");
			String cRollNo = request.getParameter("cRollNo");
			String bURegNo = request.getParameter("bURegNo");
			String tutorialGroup = request.getParameter("tutorialGroup");
			String name = request.getParameter("name");
			String fName = request.getParameter("fName");
			String fOccupation = request.getParameter("fOccupation");
			String address = request.getParameter("address");
			String contactNo = request.getParameter("contactNo");
			String day = request.getParameter("day");
			String month = request.getParameter("month");
			String year = request.getParameter("year");
			String local = request.getParameter("local");
            		String district = request.getParameter("district");
			String lT = request.getParameter("lT");
			String examPassed = request.getParameter("examPassed");
			String day1 = request.getParameter("day1");
			String month1 = request.getParameter("month1");
			String year1 = request.getParameter("year1");
			String class1 = request.getParameter("class1");
			String subject1 = request.getParameter("subject1");
			String subject2 = request.getParameter("subject2");
			String subject3 = request.getParameter("subject3");

			stmt.setInt(1,Integer.parseInt(sessionId));
			stmt.setInt(2,Integer.parseInt(cRollNo));
			stmt.setString(3,bURegNo);
			stmt.setString(4,tutorialGroup);
			stmt.setString(5,name);
			stmt.setString(6,fName);
			stmt.setString(7,fOccupation);
			stmt.setString(8,address);
			stmt.setInt(9,Integer.parseInt(contactNo));
			stmt.setInt(10,Integer.parseInt(day));
			stmt.setString(11,month);
			stmt.setInt(12,Integer.parseInt(year));
			stmt.setString(13,local);
			stmt.setString(14,district);
			stmt.setString(15,lT);
			stmt.setString(16,examPassed);
 			stmt.setInt(17,Integer.parseInt(day1));
			stmt.setString(18,month1);
			stmt.setInt(19,Integer.parseInt(year1));
			stmt.setString(20,class1);
			stmt.setString(21,subject1);
			stmt.setString(22,subject2);
			stmt.setString(23,subject3);



			int x = stmt.executeUpdate();

			if (x==1)
			{
					out.println("<center>");
					out.println("<h4>Record has been successfully added!</h4>");
					out.println("</center>");
			}


			else
			{
					out.println("<center>");
					out.println("Error adding record");
					out.println("</center>");
			}
			stmt.close();
			conn.close();
	     }
		catch(Exception e)
		{
			System.out.println(e);
		}
    }
}

[William Brogden]

If you will check the JavaDocs for java.lang.Integer you will find that parseInt can throw a NumberFormat Exception which will naturally stop execution of your method..

You will have to provide for checking all of the field values that are going to be parsed as integers.

In fact, it would be good practice to check all of the form values for valid values before modifying your database. Yes this will take a lot of coding, no there is no super simple shortcut.

Bill

[Hebert Coelho]

Hello shaz baluch,

If you take a look in my signature there is a basic servlet hello world that shows how to do this kind of action.

When you receive a string value from the the web it might come null.

You have to test the value before the parsing method be invoked.

[Rakesh Chaudhary]

Hi,

shaz baluch,

You can try validation for blank entries which looks something like the following before storing your values to the database for the values you receive.Than parse it to Integer and store it to the database.

 sessionId = (sessionId.equalsIgnoreCase("") || sessionId.equalsIgnoreCase(null)) ? "" : sessionId;

and for wrong entries ... use if else blocks as per your conditions

I hope this works.....

[Bear Bibeault]

What does the session is have to do with validating data?

[Paul Clapham]

How does equalsIgnoreCase("") work differently than equals("")? That code seems to be a convoluted and hard-to-understand rewriting of

if (sessionId == null) sessionId = "";

[Rakesh Chaudhary]

Hi Paul,

code seems to be a convoluted and hard-to-understand rewriting of

What I meant by this validation code is to check the null values coming from a dB..Sorry I read the question wrong..

But I think for other string values this guy can use my code.

How does equalsIgnoreCase("") work differently than equals("")?

I think for future reference for any kind of deep comparison ...equals may fail but equalsIgnoreCase wont ..

Please correct me if I am wrong

[Habeeb Shaikh]

Hi everybody,
If you use equalIgnoreCase() it will optimise performance instead of using equals.