I am not sure if this is a complex problem but as a starting person this seems a bit complex to me. I have an object based on which i need to show some values on the UI and let user select some of them, i need to send data back to another controller when user click on the submit button.Here is the structure of my data object

public class PrsData{
private Map<String, List<PrsCDData>> prsCDData;
}

public class PrsCDData{
  private Map<String, Collection<ConfiguredDesignData>> configuredDesignData;
}

public ConfiguredDesignData{
  // simple fields
}

I have set the object in model before showing the view like

model.addAttribute("prsData", productData.getPrData());

In the form i have following settings

<form:form method="post" commandName="prsData" action="${addProductToCartAction}" >
<form:hidden path="prsCDData['${prsCDDataMap.key}']
  [${status.index}].configuredDesignData['${configuredDesignDataMap.key}']
  [${configuredDesignDataStatus.index}].code"/>

<form:hidden path="prsCDData['${prsCDDataMap.key}']
  [${status.index}].configuredDesignData['${configuredDesignDataMap.key}']
  [${configuredDesignDataStatus.index}].description"/>

</form:form>

This is what i have at AddProductToCartController

public String addToCart(@RequestParam("productCodePost") final String code,
@ModelAttribute("prsData") final PrsData prsData, final Model model,
@RequestParam(value = "qty", required = false, defaultValue = "1") final long qty)

On submitting the form i am getting following exception

org.springframework.beans.NullValueInNestedPathException: Invalid property 'prsCDData[Forced][0]' 
of bean class [com.product.data.PrsData]: 
Cannot access indexed value of property referenced in indexed property path 'prsCDData[Forced][0]': returned null

It seems like its trying to access the values on this controller while i am trying to send value to that controller and trying to create same object with selected values

Can any one tell me where i am doing wrong and what i need to take care of