Spring List Binding

Question

Thanks in advance for any help.

I have the following object association in my model:

public class Contract {
   private Integer id;
   private String name;
   //getters/setters...
}

public class User {
   ....
   private List<Contract> contracts;
   ....
}

Controller:

@RequestMapping(....)
public String getUser(@PathVariable Integer userId, Model model) {
   ....
   model.addAttribute(userDao.findUser(userId));
   model.addAttribute("contractsList", contractDao.findAllContracts());
   ....
}

@RequestMapping(....)
public String processUser(@ModelAttribute User user, Model model) {
   ....

   //Create a copy of the user to update...
   User userToUpdate = userDao.findUser(user.getId);

   ....
   userToUpdate.setContracts(user.getContracts());
   //set other properties...

   userDao.updateUser(userToUpdate);

   return "someSuccessView";
} 

@InitBinder
protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {
   binder.registerCustomEditor(Contract.class, new UserContractsPropertyEditor());
}

My PropertyEditor:

public class UserContractsPropertyEditor extends PropertyEditorSupport {

   @Inject ContractDao contractDao;

   @Override
   public void setAsText(String text) throws IllegalArgumentException {
      System.out.println("matching value: " + text);
      if (text != "") {
         Integer contractId = new Integer(text);
         super.setValue(contractDao.findContract(contractId));
      } 
   }

}

My JSP form:

<form:form commandName="user"> 
   <%-- Other fields... --%>
   <form:checkboxes items="${contractsList}" 
      path="contracts" 
      itemValue="id" 
      itemLabel="name" />   
</form:form>

The form renders correctly. That is, the checkbox list of Contracts is generated and the correct ones are "checked." The problem is when I submit I get:

java.lang.IllegalArgumentException: 'items' must not be null
    at org.springframework.util.Assert.notNull(Assert.java:112)
    at org.springframework.web.servlet.tags.form.AbstractMultiCheckedElementTag.setItems(AbstractMultiCheckedElementTag.java:83)
    at org.apache.jsp.WEB_002dINF.jsp._005fn.forms.user_jsp._jspx_meth_form_005fcheckboxes_005f0(user_jsp.java:1192)
    ....

The custom property editor seems to be doing its job and there are no null/empty strings being passed.

If the form and controller makes the conversion when viewing the form, why is it having trouble when processing the form? What am I missing here?

ach · Accepted Answer · 2012-04-03 20:49:25Z

2

You need to ensure that a call to getContract() returns a List instance:

public List<Contract> getContracts() {
    if (contracts == null) contracts = new ArrayList<Contract>();
    return contracts;
}

answered Apr 3, 2012 at 20:49

ach

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Pcloadletter · Accepted Answer · 2012-04-04 14:10:51Z

0

Thanks for your response. I guess a fresh set of eyes first thing in the morning does the trick again.

Apparently, my custom property editor had no clue what to do with the id value I was passing in since it couldn't access my DAO/service. So, I had to change the constructor:

public class UserContractsPropertyEditor extends PropertyEditorSupport {

   private ContractDao contractDao;

   public UserContractsPropertyEditor(ContractDao contractDao) {
      this.contractDao = contractDao;
   }

   @Override
   public void setAsText(String text) throws IllegalArgumentException {
      Integer contractId = new Integer(text);
      Contract contract = contractDao.findContract(contractId);
      super.setValue(contract);
   }

}

Then, modified the initBinder in my controller:

   @Inject ContractDao contractDao;
   ....    
   @InitBinder
    protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {
       binder.registerCustomEditor(Contract.class, new UserContractsPropertyEditor(this.contractDao));
    }

Maybe this will help someone else.

answered Apr 4, 2012 at 14:10

Pcloadletter

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1 Comment

Heady Over a year ago

In case you are still active: I pretty much copied your (corrected) example and getting error 400. What is wrong?

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