NULL pointer exception.

[sunil khandelwal]

Hi,

I am very new to servlet.

I made a class to connect servlet to database bt i m getting this error.

 HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
	Mysql_connection.query(Mysql_connection.java:21)
	GetData.doPost(GetData.java:48)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.30 logs.
Apache Tomcat/5.5.30   

my servlet class GetData.java is:-

import java.io.IOException;




import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class GetData extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws IOException, ServletException {
		response.setContentType("text/html");
		
		String names[] = new String[7];
		names[0] = request.getParameter("contact_no");
		names[1] = request.getParameter("contract_tittle");
		names[2] = request.getParameter("evergreen");
		names[3] = request.getParameter("contract_val");
		names[4] = request.getParameter("contract_desc");
		names[5] = request.getParameter("exp_date");
		names[6] = request.getParameter("renew_date");

		Mysql_connection msql=new Mysql_connection();
	    try {
			msql.connection(request);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}


        String s2 = "INSERT INTO name_table (contact_no) VALUES (?)";
        try {
			msql.query(s2);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		for(int i=0;i<names.length;i++)
		{
			try {
				msql.getTextvalue(names[i]);
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		try {
			msql.Close_connection();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}    

and my database connection class Mysql_connection.java code is :-

   import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.servlet.http.HttpServletRequest;


public class Mysql_connection {
	Connection connection;
	PreparedStatement PreparedStatement;
	int i=1;	
public void connection(HttpServletRequest request) throws ClassNotFoundException, SQLException
   {
	Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
	String db = "jdbc:sqlserver://192.168.1.80:1633;DatabaseName=TEST_SUNIL";
	 connection = DriverManager.getConnection(db,"TEST_SUNIL","TEST_SUNIL");
	}
	public void query(String s) throws SQLException
	{
		 PreparedStatement = connection.prepareStatement(s);

	}
	public void getTextvalue(String s) throws SQLException
	{
		
		PreparedStatement.setString(i, s);
		PreparedStatement.executeUpdate();
		i++;
	}
   	public void Close_connection() throws SQLException
   	{
   		PreparedStatement.close();
   	}
}

 

please tell me solution ASAP


Thanks in advance.>

[Christophe Verré]

please tell me solution ASAP

Please EaseUp and UseRealWords.

[sunil khandelwal]

k.

ya next time i will do.

by ASAP my means as soon as possible.

[Nicola Garofalo]

You do not initialize Connection object, that's why you are receiving a NullPointerException

I can't see any call to the method that initializes the Connection object.

public void connection(HttpServletRequest request) throws ClassNotFoundException, SQLException

Call method connection before calling the method query

[Christophe Verré]

Nicola Garofalo wrote:I can't see any call to the method that initializes the Connection object.

Line 36

[Ananth Chellathurai]

Is your connection url and parameters valid?

[Nicola Garofalo]

Line 36...Great. Now i see it

[Steven Schwab]

In lines 35-43 of GetData, you're catching any exceptions that DriverManager.getConnection() might be throwing and just printing out stack traces.

If DriverManager.getConnection() throws an exception (and you ignore it like you are now), then Mysql_connection.connection will still be null when you try to use it in query().

Are any stack traces being printed out to the console or the log files?

[subhash kumar]

your exception catching process is not giving you the enough information about exactly where the problem is.
every where you have used throws clause
i think first catch the exception using the try/catch block and then throw the same exception in the catch block
for example:

  
public void connection(HttpServletRequest request) throws ClassNotFoundException, SQLException  
    {  
      try {     
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");  
            String db = "jdbc:sqlserver://192.168.1.80:1633;DatabaseName=TEST_SUNIL";  
            connection = DriverManager.getConnection(db,"TEST_SUNIL","TEST_SUNIL");
           }
      catch(  SQLException ex){
               ex.stackPrintTrace();
               throw ex;
             }
     }

this will give you great advantages like debugging at development time.


Please correct me if i am wrong at any place(in this concept).

[Md Haidar Ali Khan]

Christophe Verré wrote:

please tell me solution ASAP

Please EaseUp and UseRealWords.

Dear
you check out your connection Object. Might be that no connect propery.
Regards,
MD. Haidar Ali Khan