How to bind a List using @ModelAttribute to controller from a JSP form

Question

I am trying to get a list of selected candidates to my controller using @modelAttribute with their respective id and blurb. I am able to bring one Candidate correctly but i don't know how to bring a list of candidates thru... I tried to add List<> as i have shown below, but i get

ERROR - SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/panel-requests] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface] with root cause org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: Specified class is an interface

JSP -

<form:form modelAttribute="candidateAddAttribute" 
  action="/panel-requests/requests/${panelRequestForId.id}/empl" method="post">
<c:forEach items="${candidates}" var="candidates">
    <select name="employee" id="employee" disabled="disabled">
        <option value="default" selected="selected">${candidates.candidateName}</option>
    </select>
    <textarea rows="3" cols="40" id="candidateBlurb" name="candidateBlurb" 
      disabled="disabled">${candidates.candidateBlurb}</textarea>

    <textarea rows="2" cols="20" id="candidateCV" name="candidateCV"                                
      disabled="disabled">${candidates.candidateCV}</textarea>
</c:forEach>
<div id="candidateDiv" id="candidateDiv">
    <select name="employee" id="employee">
        <option value="default" selected="selected">Select Employee</option>
        <c:forEach items="${employees}" var="employee">
            <option value="${employee.id}" id="${employee.id}">
                ${employee.employeeName}- ${employee.employeeCV}<
            /option>
        </c:forEach>
    </select>   
    <textarea rows="3" cols="40" id="candidateBlurb"                
      name="candidateBlurb">BLURB</textarea>
    <div id="employeeCv"></div>
    <input type="submit" value="Add Candidate" />
</div>
</form:form>

The above form at first displays list of employee and when user selects employee, enters blurb and hits add candidate button, i take data to controller.

Controller:

@RequestMapping(value = "{id}/empl", method = RequestMethod.POST)
public String getEmployeeDetails(
    @ModelAttribute("candidateAddAttribute") @Valid List<Candidate> candidates,
    BindingResult result, @PathVariable("id") int requestId, Model model) {

        //implementation goes here
}

How do I implement List in this case? Thanks in advance.

EDITED PART I tried sending 2 candidate's details, firebug sends it correctly like - Parameters candidateBlurb BLURB sar candidateBlurb BLURB dann employee 1 employee 2

so it can be a problem in initBinder that i ma using, binder.registerCustomEditor(Employee.class, new PropertyEditorSupport() { public String getAsText() { return Long.toString(((Employee) getValue()).getId()); }

                public void setAsText(final String text) {
                    Employee employee = Employee.findById(Integer
                            .parseInt(text));
                    setValue(employee);
                }
            });

which only takes 1 employee detail at a time. Is that a problem here???

matt b · Accepted Answer · 2011-07-06 23:52:27Z

5

Create a POJO class which contains the List as a property, such as

public class EmployeeForm {
     private List<Candidate> candidates;
     public List<Candidate> getCandidates() { ... }
     public void setCandidates(List<Candidates>) { ... }
}

and use this in your @RequestMapping method's signature rather than a List<Candidate> directly.

The error message you get is Spring complaining that it doesn't know how to instantiate a List interface, in order for Spring to bind the request parameters in the form to it. You want to provide a simple form/command class to data-bind the form parameters to, Spring knows how to handle a list from there.

answered Jul 6, 2011 at 23:52

matt b

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8 Comments

saran Over a year ago

Hi, i tried as u adviced, but i might be wrong somewhr, cud u plz guide me?

saran Over a year ago

public class EmployeeForm { private static final Logger LOG = Logger.getLogger(EmployeeForm.class); private List<Candidate> candidates = new ArrayList<Candidate>(); public List<Candidate> getCandidates() { return candidates; } public void setCandidates(List<Candidate> candidates) { this.candidates = candidates; } } @RequestMapping(value = "{id}/empl", method = RequestMethod.POST) public String getEmployeeDetails( @ModelAttribute("candidateAddAttribute") @Valid EmployeeForm candidates, BindingResult result, @PathVariable("id") int requestId, Model model) {//code}

saran Over a year ago

when i debug the above code, candidates is null when i try to use it in my controller... shud i change something in the code?

saran Over a year ago

also, when i try to see LOG.error(candidates.getCandidates().get(0).getCandidateBlurb()); in my controller, i get ERROR - SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/panel-requests] threw exception [Request processing failed; nested exception is java.lang.IndexOutOfBoundsException: Index: 0, Size: 0] with root cause java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

matt b Over a year ago

what does the form data sent in the request look like? IIRC you should have a list of items like candidates[0].name, candidates[0].age, candidates[1].name etc

|

animuson · Accepted Answer · 2011-11-29 07:51:48Z

0

you can try this :

List<Candidate> candidates = ListUtils.lazyList(new ArrayList<Candidate>(),FactoryUtils.instantiateFactory(Candidate.class));

edited Nov 29, 2011 at 7:51

animuson♦

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answered Nov 29, 2011 at 7:35

wangjin

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Comments

Trevor · Accepted Answer · 2012-06-27 00:31:01Z

0

I've run into this same issue, half of the fields are binding correctly and half aren't. I noticed that the half that are not binding correctly (thus giving me NULL in the controller) were wrapped in a DIV.

When I moved these fields outside the DIV, bingo, they were bound properly in the controller.

I see that you have some fields wrapped in a DIV too, I'd recommend moving them out and seeing if they become visible to your controller.

answered Jun 27, 2012 at 0:31

Trevor

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