Day: October 30, 2021

I have a program that displays a list of vaccines and for each vaccine listed in the table, you can edit them. When I click on edit for the specified vaccine, one of the values allowed to be modified is the number of doses required, which can be changed from a drop down list. I'm having trouble being able to pass that value selected to the doPost method, as when I try changing, it goes back to the main page and shows the value for doses required as null. How can I fix this?

Here's the main vaccine list servlet:

package vaccineList.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import NewVaccine.servlet.NewVaccine;
import NewDose.servlet.NewDose;

//import cs3220.model.GuestBookEntry;
//import cs3220.utilities.*;

@WebServlet(urlPatterns = "/ListVaccine", loadOnStartup = 1)
public class ListVaccine extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public ListVaccine()
    {
        super();
    }

    public void init( ServletConfig config ) throws ServletException
    {
        super.init( config );

        List<VaccineEntry> entries = new ArrayList<VaccineEntry>();
        entries.add( new VaccineEntry( "Pfizer/BioNTech", "2", "21", "10000", "10000" ) );
        entries.add( new VaccineEntry( "Johnson&Johnson", "1", "0", "5000", "5000"  ) );

        getServletContext().setAttribute( ServletFunctions.VaccineEntries, entries );
    }

    @SuppressWarnings("unchecked")
    protected void doGet( HttpServletRequest request,
        HttpServletResponse response ) throws ServletException, IOException
    {
        StringBuilder html = new StringBuilder();
        List<VaccineEntry> entries = ServletFunctions.getVaccineEntriesFromServletContext(getServletContext());

        response.setContentType( "text/html" );
        PrintWriter out = response.getWriter();

        html.append( "<p>List Vaccine</p>" );

        html.append( "<p><a href='NewVaccine'>New Vaccine</a> |" );
        html.append( "<a href='NewDose'> New Dose</a></p>" );

        html.append("<table border='1'>");

        html.append("<tr>");
        html.append( "<td>   " + " <b>Vaccine</b>   </td>" );
        html.append( "<td>" + " <b>Doses Required</b></td>" );
        html.append( "<td>" + " <b>Days Between Doses</b></td>" );
        html.append( "<td>" + " <b>Total Doses Recieved</b></td>" );
        html.append( "<td>" + " <b>Total Doses Left</b></td>" );
        html.append("<td></td>" );
        html.append( "</tr>" );

        for( VaccineEntry entry : entries )
        {

            html.append("<tr>");
            html.append( "<td>" + entry.getName() + "</td>" );
            html.append( "<td>" + entry.getDosesReq() + "</td>" );
            if(entry.getDaysBtwnDoses() == "0") {
                html.append( "<td></td>" );
            }
            else
                html.append( "<td>" + entry.getDaysBtwnDoses() + "</td>" );


            html.append( "<td>" + entry.getTotalDosesRecieved() + "</td>" );
            html.append( "<td>" + entry.getTotalDosesLeft() + "</td>" );


            html.append( "<td><a href='editVaccine?id=" + entry.getId() + "&dosesReq=" + entry.getDosesReq() + "'>Edit</a></td>"  );


            html.append( "</td>" );
            html.append( "</tr>" );
        }
        html.append( "</table>" );



        out.println( ServletFunctions.titleWithBody("ListVaccine", html.toString()) );
    }

}

and here's the edit vaccine page:

package EditVaccine.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

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


import vaccineList.servlet.*;


@WebServlet("/editVaccine")
public class editVaccine extends HttpServlet {
    private static final long serialVersionUID = 1L;


    public editVaccine() {
        super();

    }

    @SuppressWarnings("unchecked")
    private VaccineEntry getEntry( int id )
    {
        List<VaccineEntry> entries = (List<VaccineEntry>) getServletContext()
            .getAttribute( "entries" );
        System.out.println("entry taken is " + id);


        for( VaccineEntry entry : entries )
            if( entry.getId() == id ) return entry;
        return null;
    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        StringBuilder html = new StringBuilder();

        String id = request.getParameter( "id" );
        String dosesReq = request.getParameter("dosesReq");
        VaccineEntry entry = getEntry(Integer.parseInt(id));
        System.out.println("The value of id is " + id);
        System.out.println("The value of dosesReq is " + dosesReq);


        System.out.println("The value of getEntry is " + entry.getId());

        response.setContentType( "text/html" );
        PrintWriter out = response.getWriter();

        html.append("<form action='editVaccine' method='post'>" );
        html.append("<table border='1' cellpadding='2'>");
        html.append("<tr>" + "<th colspan='2'>Name</th>");
        html.append("<input type='hidden' value='" + id + "' name='id' id='id' />");
        html.append("<input type='hidden' value='" + dosesReq + "' name='dosesReq' id='dosesReq' />");
        html.append("<td><input type='text' name='name' value=" + entry.getName() + "></input></td>" + "</tr>");
        html.append("<tr><th colspan='2'>Doses Required</th>" + "<td><select id='dosesReq' name='dosesReq' " + "'>"); 
        html.append("<option value='1'" + "'>1</option>");
        html.append("<option value='2'" + "'>2</option>");
        html.append("<option value='3'" + "'>3</option>");
        html.append("</select></td>");
        html.append("<tr><th colspan='2'>Days Between Doses</th><td><input type='text' name= 'DaysBtwnDoses' value='" + entry.getDaysBtwnDoses() + "'> </input></td></tr>");
        html.append("<td colspan = '2'><button>Save</button></td>");
        html.append("</form>");
        html.append("</table>");


        out.println( ServletFunctions.titleWithBody("ListVaccine", html.toString()) );

       String[] dropDown = request.getParameterValues("dosesReq");
       System.out.println("dropdown:" + dropDown);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        VaccineEntry entry = getEntry(Integer.parseInt(request.getParameter("id")));

        entry.setName(request.getParameter("name"));
        entry.setDosesReq(request.getParameter("dosesReq"));
        String name = entry.getName();
        System.out.println("name is " + name);
        entry.setDosesReq(request.getParameter("dosage"));
        String dosage = entry.getDosesReq();
        System.out.println("dosage is " + dosage);
        entry.setDaysBtwnDoses(request.getParameter("DaysBtwnDoses"));
        String DaysBtwnDoses = entry.getDaysBtwnDoses();
        System.out.println("DaysBtwnDoses is " + DaysBtwnDoses);

        response.sendRedirect("ListVaccine");
        return;

    }

}