AngularJS JSON Isis - Can't retrieved JSON data in Restful Object server as String

Question

I am sending the following JSON data to an RO Server :

var basketItem= {  x:x1, y:y1 };                     

var basketItemByStop=
 {                     

        sessionId : {
        id : "sessionId",
        memberType : "property",
        value : '3432345ADC'
         },
        customerId : {
        id : "customerId",
        memberType: "property",
        value : '123456'
        },
        email : {
        id : "email",
        memberType : "property",
        value : "x.y@x.net"
        },
        basketItem : {
        "id" : "basketItem",
        "memberType" : "property",
        "format" : "string",
        "extensions" : {"x-isis-format" : "string"},
        "value" : basketItem
       }          
};

In the action class I tried retrieving the basketItem as a string, but I am getting the following error:

"invalidReason":"Failed to parse representation as value of type 'String'"},"x-ro-invalidReason":"Basket Item is mandatory"}

My action method defintion

@Bookmarkable
    @ActionSemantics(Of.IDEMPOTENT)
    @MemberOrder(sequence = "1")
    @Named("View Basket")
    @PublishedAction
    public final ShoppingBasket getBasket(
            @Named("Session ID") final String sessionID,
            @Named("Customer ID") final String customerID,
            @Named("Email") final String email,
            @Named("Basket Item") final String JSONData) {
}

The main problem is the JSONData parameter is coming across as [object object] in the method and using toString() does not convert it to a normal string. I need it as a normal human readable json and pass it to my Jackson JSON parser for further processing. Any ideas anyone ... Thanks.