Spring MVC 3: Property referenced in indexed property path is neither an array nor a List nor a Map

JQuery's $.ajax does an excellent job mapping a json object to parameters, but when you start getting into more complex objects Spring MVC doesn't know how to interpret it sometimes.

For example if you have a json object like:

{
   "beans":[
      {
         "agreemendId":1,
         "answerId":2
      }
   ]
}

JQuery will map your parameters like

beans[0][agreementId]:1
beans[0][answerId]:2

The problem is that Spring MVC is expecting a parameter format like

beans[0].agreementId:1
beans[0].answerId:2

In order to get that you can do it in 1 of two ways. You can do the quick and dirty way, which changes the way you're building your json object. Or, the other way is to extend the jQuery plugin to build parameters differently.

To change the javascript code was pretty simple and looked something like this

var answers = {};
answers['beans[' + index +'].agreementId'] = agreementId;
answers['beans[' + index +'].answerId'] = value;

To modify the jquery plugin I would suggest taking a look here.

And for reference here are the pojos I was mapping to.