I’m using a multiple select HTML form input to allow a user to pick a collection of Extensions from a list of all possible Extensions.
The Extension class is quite simple –
public class Extension {
private String number;
private String firstName;
private String lastName;
... getters and setters ...
@Override
public String toString() {
return new StringBuilder(number).append(" - ")
.append(firstName).append(" ").append(lastName)
.toString();
}
}
Here’s my form object –
public class BusinessUnitForm {
private String name;
private Collection<Extension> extensions;
public Collection<Extension> getExtensions() {
return extensions;
}
public void setExtensions(Collection<Extension> extensions) {
this.extensions = extensions;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
And the controller –
@Controller
@RequestMapping("/businessunit")
public class BusinessUnitController {
... extension service & getters/setters ...
@RequestMapping(method = RequestMethod.GET)
public ModelAndView showForm(HttpServletRequest request, HttpServletResponse response) throws Exception {
Integer customerId = (Integer) request.getSession().getAttribute("customerId");
ModelAndView mav = new ModelAndView("bu");
// this is quite expensive...
Collection<Extension> allExtensions = extensionService.getAllExtensions(customerId);
BusinessUnitForm businessUnitForm = new BusinessUnitForm();
mav.addObject("allExtensions", allExtensions);
mav.addObject("businessUnitForm", businessUnitForm);
return mav;
}
@RequestMapping(value="/create", method = RequestMethod.POST)
public ModelAndView create(HttpServletRequest request, HttpServletResponse response, BusinessUnitForm businessUnitForm, BindingResult result) throws Exception {
// *** BREAKPOINT HERE *** to examine businessUnitForm
Integer tenantId = (Integer) request.getSession().getAttribute("tenantId");
// code to process submission
ModelAndView mav = new ModelAndView("bu");
return mav;
}
}
And finally the view –
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring" %>
<html>
...
<form:form action="businessunit/create" method="POST" commandName="businessUnitForm" >
<form:label path="name"></form:label><form:input path="name" />
<form:select path="extensions" cssClass="multiselect">
<form:options items="${allExtensions}" itemValue="number" />
</form:select>
<input type="submit" value="Create" />
</form:form>
...
</html>
At the breakpoint shown above in the create controller method, businessUnitForm.extensions is null. businessUnitForm.name is bound correctly.
I’ve tried, perhaps misguidedly, making businessUnitForm.extensions a LazyList but this doesn’t help.
If I change BusinessUnitForm.extensions to be a Collection of unspecified type, it is populated successfully with a LinkedHashSet of Strings, containing the values selected.
Maybe I’m expecting too much of Spring, but I was hoping it would be able to use the values from the select, and also the reference data in allExtensions to automagically create a Collection<Extension> for me on the businessUnitForm. I understand the role of CustomCollectionEditors, but was under the impression that this might not be required in Spring 3.
Can Spring 3 populate my Collection<Extension> on the BusinessUnitForm without me writing a custom collection editor ? Some kind of trick with the view, perhaps ?
Thanks in advance …
Dan
You need to implement a custom converter that is able to convert the String from the request into an
Extensionobject.And then you must use Collection (or List, or Set) with generic type information.
See this answer for an example of an converter: Submit Spring Form using Ajax where Entity has Foreign Entities