Populating dropdown with database entries

Question

I am trying to poulate the database GroupNames in my dropdown using servlets. How to do it? Please help

In my jsp file am having :

 <%
ArrayList<String> list1 = (ArrayList<String>)request.getAttribute("res1");
 %>
<select name="GName" >
<%
    for(String list:list1)  
{ %>
<option><%=list%></option>

<% } 
%>

In my servlet i fetched all the database names in an arraylist like this :

   ArrayList<String> list = new ArrayList<String>();
            out.println("HI GROUP MEMBER");
            String query="Select GNAME from tbGroup";
            ps = con.prepareStatement(query);
            rs=ps.executeQuery();
            while(rs.next()){
                list.add(rs.getString("GNAME"));


            }
            String[] arr1 = list.toArray(new String[list.size()]);
            request.setAttribute("res1",arr1);

            int i;
            for(i=0;i<list.size();i++){
                out.println(arr1[i]);
            }

Now am getting null pointer exception in it.Please help what can be the reason for it ?

Here is complete error :

Stacktrace:] with root cause
java.lang.NullPointerException
at org.apache.jsp.GroupLoginScreen_jsp._jspService(GroupLoginScreen_jsp.java:91)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:563)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:399)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:317)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:204)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:311)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)

easier to learn how to use a MVC framework such as struts, stripes or Spring MVC — Scary Wombat, Mar 26 '14 at 04:46
@user3462609 you really need to learn about web technologies. — Scary Wombat, Mar 26 '14 at 04:52
@Java1 yeah. i knew am week at it.I edited my code but still it gives an exception.Could u please help — user3462609, Mar 26 '14 at 05:07
@user3462609 why you converting `List` to `String[]` no need you can use the List in jsp. — Abhishek Nayak, Mar 26 '14 at 05:38

Deepu--Java · Accepted Answer · 2014-03-26T06:00:58.893

0

<%
    ArrayList<String> list1 = (ArrayList<String>)request.getAttribute("res1");
 %>
<select name="GName" >
    <%
        for(String list:list1)  
    { %>
    <option><%=list%></option>

   <% } 
    %>
</select>

Use this in your JSP. Servlet Code

            ArrayList<String> list = new ArrayList<String>();
            out.println("HI GROUP MEMBER");
            String query="Select GNAME from tbGroup";
            ps = con.prepareStatement(query);
            rs=ps.executeQuery();
            while(rs.next()){
                list.add(rs.getString("GNAME"));
            }
            request.setAttribute("res1",list);
            RequestDispatcher rd= context.getRequestDispatcher("GroupLoginScreen.jsp");
            rd.forward(request, response);

edited Mar 26 '14 at 06:00

answered Mar 26 '14 at 05:15

Deepu--Java

3,742
3
19
30

Still the same exception. – user3462609 Mar 26 '14 at 05:28
@user3462609 post the exception in your question. – Deepu--Java Mar 26 '14 at 05:35
i posted my question with ti – user3462609 Mar 26 '14 at 05:39
@user3462609 Now try this servlet code also. – Deepu--Java Mar 26 '14 at 05:44
If not working then please post complete Error Trace. – Deepu--Java Mar 26 '14 at 05:44
I edited it.You can see it now – user3462609 Mar 26 '14 at 05:51
@user3462609 how are you redirecting the request from servlet to JSP? – Deepu--Java Mar 26 '14 at 05:53
response.sendRedirect("GroupLoginScreen.jsp"); – user3462609 Mar 26 '14 at 05:57
@user3462609 don't use sendredirect, se the updated answer. Now it should work. – Deepu--Java Mar 26 '14 at 06:01

score 0 · Answer 2 · edited May 23 '17 at 12:12

0

populate by using jstl:

add

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

in top of jsp.

then, populate the select box like:

<select>
  <option value="NONE">--None--</option>
  <c:forEach items="${res1}" var="itm">
    <option value="${itm}">${itm}</option>
  </c:forEach>
</select>

and in your servlet:

after retrived the elements add the list in request:

request.setAttribute("res1",list);

Note: add jstl.jar in your classpath to use c: tag, and avoid scriptlets in jsp

edited May 23 '17 at 12:12

Community

1
1

answered Mar 26 '14 at 05:35

Abhishek Nayak

3,732
3
33
64

I tried this it gives following exception : org.apache.jasper.JasperException: The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application – user3462609 Mar 26 '14 at 05:42
@user3462609 you have not added jstl in your classpath, add it link added in top check out in answer. – Abhishek Nayak Mar 26 '14 at 05:45
It shows only NONE in dropdown – user3462609 Mar 26 '14 at 05:55
@user3462609 then you list is empty, check out. – Abhishek Nayak Mar 26 '14 at 06:06

Populating dropdown with database entries

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