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Editorial Team
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Asked: 2026-06-05T22:04:02+00:00

I’m new to learning JSPs and Servlets. I have a Java class which calls

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I’m new to learning JSPs and Servlets. I have a Java class which calls a stored procedure and return a list of states from a database (this is my test case while I learn, other more complex actions will come later). The list of states should be returned to a JSP for display/use in a form, etc… For now, I’m happy to just get the data printing via the JSP page to know it is there.

However, when I call the Java code from the JSP, it appears that the result object is returned as null and thus no data is accessible. I’ve tried to return the data as a ResultSet object as well, but the results are the same. I do know the stored procedure works when called from SQL. Additionally I have the Java code as a servlet that responds to a doPost request and that works fine…

What might I be missing / failing to understand? Is this possible? 

package edu.XXXX.ais.userapp;

import java.sql.*;
import java.util.*;

public class DBQueries {

    public static Vector<String> getStatesList() {
        Vector<String> results = new Vector<String>();
        Connection con = null;  
        try {

            // Example of executing a stored procedure
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection ("jdbc:mysql://hostname:3306/dbName","username","password");
            CallableStatement cs = con.prepareCall("{call getStatesList()}");
            ResultSet rs = cs.getResultSet();

            while (rs.next()) {
                results.add(rs.getString(1));
            }
        } catch (SQLException e) {
            System.err.println("Servlet could not display records." + e);

        } catch (ClassNotFoundException e) {
            System.err.println("JDBC driver not found." + e);

        } finally {
            try {
                if (con != null) {
                    con.close();
                    con = null;
                }

            } catch (SQLException e) {
                System.err.println(e);
            }
        }
        return results;
    }
}

JSP page that calls the above Java code (expects to be able to receive results…)

<html>
<head>
<title>Foo</title>
</head>

<body>
<h3>List of states via a servlet call to the database</h3>
<%@ page import="java.util.*" %>
<%@ page import="edu.XXXX.ais.userapp.DBQueries" %>

<%
    Vector rs = DBQueries.getStatesList();
    if (rs != null)
        for (int index = 0; index < rs.size(); index++) {
            out.println("Name : " + (String) rs.get(index));
        }
%>

</body>
</html>

The resulting Tomcat errors are as follows:

org.apache.jasper.JasperException: An exception occurred processing JSP page /states.jsp at line 12

9: <%@ page import="edu.XXXX.ais.userapp.DBQueries" %>
10: 
11: <%
12:     Vector rs = DBQueries.getStatesList();
13:     if (rs != null)
14:         for (int index = 0; index < rs.size(); index++) {
15:             out.println("Name : " + (String) rs.get(index));


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause

java.lang.NullPointerException
    edu.XXXX.ais.userapp.DBQueries.getStatesList(Unknown Source)
    org.apache.jsp.states_jsp._jspService(states_jsp.java:75)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
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1 Answer

  1. Editorial Team

    In your sample code, the CallableStatement is not executed before cs.getResultSet(), so rs will be null, and then NullPointerException will occur when executing rs.next().

    CallableStatement cs = con.prepareCall("{call getStatesList()}");
boolean bIsResultSetOrNot = cs.execute (); // <-- missed
ResultSet rs = cs.getResultSet();

    Make sure the statement is executed, and make sure the execute result is ResultSet not an update count.

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