JSON Representation of HashMap

It should be like this

{ "userPreferences":{"mobile":"yes","email":"yes"} }

"userPreferences":{"mobile":"yes","email":"yes"}

The JSON you have would be invalid even as a JavaScript object, since you haven't defined property names for the two "inner" objects. A HashMap is basically a set of key-value pairs. Your JSON should look like:

"userPreferences": {
    "mobile": "yes",
    "email": "yes"
}