Spring MVC null attribute in my @modelAttribute object sended to the controller

Question

I'm trying to use @modelAttribute to send my model attributes to the controller

my model contains many attributes (String, Integer,..) one of them is an object that i want to retrieve from a select tag. the problem is when i pass the modelattribute to the controller my object is Null

JSP:

<form:form method="post" action="saveUorg.html"  modelAttribute="uorg" >
<table >
<tr>
    <th>Nom</th>
    <th>Nom abregé</th>
    <th>timbre</th>
    <th>Date début effet</th>
    <th>Date fin effet</th>
</tr>
<tr>
    <td><input  path="nom" name="nom"/></td>
    <td><input  path="nomAbrege" name="nomAbrege"/></td>
    <td><input  path="timbre" name="timbre"/></td>
    <td><input  type="date" path="dateDebutEffet" name="dateDebutEffet"/></td>
    <td><input  type="date" path="dateFinEffet" name="dateFinEffet"/></td>
 </tr>
</table> 
<table >
<tr>
    <th>email</th>
    <th>Unité père</th>
</tr>
<tr>
    <td><input  path="email" name="email"/></td>
    <td><select  path="refUniteOrganisParent">
        <option  value="-"> --- </option> 
      <c:forEach items="${listeuos}" var="uorgg" varStatus="status" >
        <option  value="${uorgg}">${uorgg} </option> 
      </c:forEach>
    </select></td>
 </tr>

this is my controller

    @RequestMapping(value ="/saveUorg", method = RequestMethod.POST)
    public ModelAndView saveUorg(@ModelAttribute("uorg") UorgVO uorg,BindingResult result){


        System.out.println("RefUniteOrganisParent:" +uorg.getRefUniteOrganisParent());


        return new ModelAndView("view","uorg",uorg);    
    }   

refUniteOragnisParent is the null object, when i print the content result in my controller of uorg.refUniteOrganisParent the result is null. Thank's in advance for help.

Answer 1

First your select tag does not have a name attribute.

Second when a form is submitted the controller only gets strings. Spring has to convert every parameter to the type you want. It has built-in converters for simple types like Integer or Boolean, but not for complex types, not to mention your own types.

So if the attribute refUniteOrganisParent is an object and only represented by a single value (the option value) you need to implement a converter that creates an instance based on this value:

public class StringToMyType implements Converter<String, MyType> { ...

http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/validation.html#core-convert

And you need to register your Converter: http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/mvc.html#mvc-config-customize

Answer 2

In your controller,the model attribute object should be like this:

        @RequestMapping(value ="/saveUorg", method = RequestMethod.POST)
       public ModelAndView saveUorg(@ModelAttribute("uorg") UorgVO uorg,BindingResult result){

          ModelAndView mav = new ModelAndView("view");              
          mav.addObject("uorg",uorg);
          System.out.println("RefUniteOrganisParent:" +uorg.getRefUniteOrganisParent());

    return mav;    
}