How to get Dynamic Drop Down Box in JSP

Question

I want to populate a dropdown box in Spring MVC i tried to do this but i am getting null pointer exception

this is my controller:

public class CatalogueController  {
private CatalogueService catalogueService;
private PublisherService publisherService;
private SubjectService subjectService; 

   // some code and i generated setter and getter methods  
   ............

 @RequestMapping(value="/catalogue/new.action", method=RequestMethod.GET)  
   public ModelAndView newMember() throws Exception {
    ModelAndView mvc= null;
    mvc =   new ModelAndView("catalogue/catalogueForm", "catalogueForm", new CatalogueBase());
    mvc.addObject("copyDetailForm", new CatalogueCopyDetails());

    List<Publisher> publist = publisherService.getPublisherList();
    mvc.addObject("publist", publist);

    List<Subject> subjectlist = subjectService.getSubjectList();
    mvc.addObject("subjectlist", subjectlist);

    return mvc;
}

this is my service method :

    @Override
public List<Publisher> getPublisherList() {
    List<Publisher> list = publisherDAO.getPublisher();
    return list;
}
    @Override
public List<Subject> getSubjectList() {
    List<Subject> list = subjectDAO.getSubjects();
    return list;
}

this is my DAO Method:

    @SuppressWarnings("unchecked")
public List<Publisher> getPublisher() {
      Query qry = getSession().createQuery("from Publisher");
        return qry.list();
}
    @SuppressWarnings("unchecked")
public List<Subject> getSubjects() {
      Query qry = getSession().createQuery("from Subject");
        return qry.list();
}

finally this is my JSP page :

  <form:form commandname="catalogueForm"    action="${pageContext.request.contextPath}/catalogue/create.action" method="post" modelAttribute="catalogueForm">

    <form:select path="publisher.id" id="publisher.id">
    <form:options items="${publist}" itemValue="id" itemLabel="name" />
    </form:select>                                                        

    <form:select path="subject.id" id="subject.id">                            
    <form:options items="${subjectlist}" itemValue="id" itemLabel="name" />
    </form:select>

   </form:form>

This is Stack Trace:

java.lang.NullPointerException at com.easylib.elibrary.webapp.controller.catalogue.CatalogueController.newMember(CatalogueController.java:80) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:100) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:604) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:565) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)

ajames ajames · Accepted Answer · 2013-06-27T11:58:19

You are getting the npe at line 80 of your controller, but I can't see which line that is in your question.

My guess is that you haven't wired in your services correctly and either "publisherService" or "subjectService" is null.

How to get Dynamic Drop Down Box in JSP

1 Answers