java.lang.NullPointerException in servlet

Question

When I run my servlet I get this error in my Tomcat console. I guess I have to look at my SimpleDateformat, but can anyone see what is wrong here? My code is compiling fine, so I am a little in doubt what to look after:

Video of the error: https://www.youtube.com/watch?v=3hdmIkwuB6k&feature=youtu.be

Have a nice day/evening to everybody From Julie

My Servlet:

package WorkPackage;

import java.io.*;
import java.sql.*;
import java.text.SimpleDateFormat;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;

@WebServlet("/getHoursSQL")
public class getHoursSQL extends HttpServlet{

    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest req, HttpServletResponse res) 
        throws ServletException, IOException{

        String connectionURL = "jdbc:mysql://localhost/NekiWork";
        Connection connection=null;

        try {
            //Load database driver
            Class.forName("com.mysql.jdbc.Driver");
            //Connection to the database
            connection = DriverManager.getConnection(connectionURL, "root", ""); 
            //Getting the data from database

            String sql = "SELECT *, (Day_hours + (Day_minutes / 60)) AS Allday_hours FROM Workdata "
                    + "WHERE startdate = ? AND endDate = ? ";
            PreparedStatement pst = connection.prepareStatement(sql);

            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");

            java.util.Date util_StartDate = format.parse( req.getParameter("startDate") );
            java.sql.Date sql_StartDate = new java.sql.Date( util_StartDate.getTime() );

            java.util.Date util_EndDate = format.parse( req.getParameter("endDate") );
            java.sql.Date sql_EndDate = new java.sql.Date( util_EndDate.getTime() );
                pst.setDate( 1, sql_StartDate );
                pst.setDate(2, sql_EndDate );

            //Show the result from database
                ResultSet rs = pst.executeQuery();

            float Allday_hours_sum = 0;
                while (rs.next()){                                      
                    Allday_hours_sum += rs.getFloat("Allday_hours"); 

                }   
                res.setContentType("text/html;charset=UTF-8");          
                res.getWriter().print(Allday_hours_sum); 

                pst.close();

        }
        catch(ClassNotFoundException e){

            System.out.println("Couldn't load database driver: " + e.getMessage());
        }
        catch(SQLException e){
            System.out.println("SQLException caught: " + e.getMessage());
        }
        catch (Exception e){
            e.printStackTrace();
        }
        finally {

            try {
                if (connection != null) connection.close();
            }
            catch (SQLException ignored){
                System.out.println(ignored);
            }
        }
    }
}

Javascript:

    <form id="myForm">
        <input type="text" id="startDate"/>                     
        <input type="text" id="endDate"/>
    </form>
    <div id="startresult"></div>
    <div id="endresult"></div>
    <script>

    $(function(){
        $("#startDate").datepicker({
            dateFormat: 'yy-mm-dd',
            onSelect: function(dateText,inst){
                $('.selected-date').html(dateText);
                 var JSON = $('#myForm').serializeArray(); //you forgot to create JSON data
                $.ajax({
                      url: "../getHoursSQL",
                      type: "post",
                      data: JSON,
                      success: function(data){
                          start: $("#startDate").val();
                          alert("success");
                          $("#startresult").html(data);

                      },
                      error:function(){
                          alert("failure");
                          $("#startresult").html('there is error while submit');
                      }  
                    });
            }
        });
    });

    $(function(){
        $("#endDate").datepicker({
            dateFormat: 'yy-mm-dd',
            onSelect: function(dateText,inst){
                $('.selected-date').html(dateText);
                 var JSON = $('#myForm').serializeArray(); //you forgot to create JSON data
                $.ajax({
                      url: "../getHoursSQL",
                      type: "post",
                      data: JSON,
                      success: function(data){
                          start: $("#endDate").val();
                          alert("success");
                          $("#startresult").html(data);

                      },
                      error:function(){
                          alert("failure");
                          $("#startresult").html('there is error while submit');
                      }  
                    });
            }
        });
    });

</script>

New console error with new javascript code:

java.lang.NullPointerException
at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1234)
at java.text.DateFormat.parse(DateFormat.java:335)
at WorkPackage.getHoursSQL.doPost(getHoursSQL.java:40)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:695)

Solution

I think there is no parameter with 'startDate' (which makes req.getParameter("startDate") return null) there for causing SimpleDateFormat to throw a NullPointerException

Comments

[Julie24]

Hello. Thanks a lot for your answer. the startDate and endDate should be in my: <form> <input id="startDate"/> <input id="endDate"/> </form> and in the javascript?

[geoand]

It should definitely be the form whose input is sent to the Servlet. I don't know what how you are handling your UI, but Javascript is needed just to submit values for in a form to a Servlet.

[Abhishek Nayak]

@Julie24 check updated answer

[Julie24]

I am handling my javascript as a calendar like this: postimg.org/image/spe7u93nh

[Abhishek Nayak]

@Julie24 you have not given form id to serializeArray("#endDate") endDate is not form id.. check my updated answer there is html form with id

[geoand]

Are you sure that input elements for the dates are inside the form?

[Abhishek Nayak]

@Julie24 you mean still NullPointerException getting in Console?

[Julie24]

They should be: <form id="myForm"> <input type="text" id="startDate"/> <input type="text" id="endDate"/> </form> <div id="startresult"></div> <div id="endresult"></div>

[Julie24]

I have just made a short video of what happenes when I run the code, if that helps anything in my question. Yes I will try to find out to do that. I will write in 5 minutes again here

[Julie24]

Shouldn't it go here:onSelect: function(dateText,inst){ $('.selected-date').html(dateText); var JSON = $('#myForm').serializeArray(); Console.log(JSON); $.ajax({

[Abhishek Nayak]

@Julie24 k, the problem is when you select startDate AJAX request is triggered, that time endDate is null because you have not selected the endDate, So do one thing trigger the AJAX request when endDate is selected..

[Julie24]

In my javascript I have 2 functions. One with startDate and one with endDate. The endDate should be triggered when I choose the second form as I see it?

[Abhishek Nayak]

let us continue this discussion in chat

[Abhishek Nayak]

@Julie24 if any answer solved your problem mark it as answer.