How Work's @ModelAttribute?

**obrienne** · Nov 15th, 2012, 12:02 PM

Hi, im new in springsource MVC, and im getting troubles with the @ModelAttribute.
From the doc's and a few tutorials and post's in forums i suppose the use of @ModelAttribute like the following:

HomeController

Code:

@Controller
public class HomeController {
@ModelAttribute("centro")
	public String getCentro(){
		return new String();
	}
@RequestMapping(value = "/", method = RequestMethod.GET)
	public String home(Locale locale, Model model) {

		String centro = "00";
		model.addAttribute("centro",centro);		
		return "home";
	}
@RequestMapping(value = "/home", method = RequestMethod.POST)
	public String home(@ModelAttribute("centro") String centro,BindingResult result, Model model) {
		
		model.addAttribute("centro",centro+"#");		
		return "home";
	}
}

home.jsp

Code:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page session="false" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<html>
<head>
<link rel="stylesheet" type="text/css" href="<c:url value="/resources/estilos.css" />" />
	<title>CE</title>
</head>
<body>
<form:form  modelAttribute="centro" method="POST" action="home" >
<h1>
	Consumos Eléctricos  
</h1>
<a href="usuarios">Usuarios</a> 
<p> <a href="centros">Centros</a> </p>
<input name="Centro" value="${centro}"/>
<input type="submit" name="submit" value="Submit!" /> 
</form:form>
</body>
</html>

But when i get the POST on Controller the String variable "centro", not back filled with the user input.
Im missing something??

Thank's for your time.

**obrienne** · Dec 20th, 2012, 02:05 AM

I respond me, for all ppl has the same issue.
You need to use <form:hidden path="*" /> where * is the model property wants to be propagated.

if model is "centro" and has a field called "fieldcentro":

Code:

<form:form  model="centro" method="POST" action="home" >
<form:hidden path="fieldcentro"/>

if model contain Lists(model has a .getList() property), varStatus contains your index:

Code:

...
<c:forEach items="${command.getLf()}" var="fmam" varStatus="status">
			<tr align="center">
				<!-- <td>  	<c:out value="${fmam.id}"/></td> -->
			   
				<td><c:out value="${fmam.centro}" />
		<form:hidden path="Lf[${status.index}].centro"/>
....

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