Key value pair from object array

Hi,
I would like to create the below outbound message from an incoming object array.

{
    "root": {
        "elementName": {
            "@attributeName": "attributeValue",
            "$": "elementValue"
        },
        "repeatedElement": [
            {
                "key": {
                    "@attr": "attr1",
                    "$": "key1"
                },
                "value": "value1"
            },
            {
                "key": {
                    "@attr": "attr2",
                    "$": "key2"
                },
                "value": "value2"
            }
        ]
    }
}

Any suggestion please on the repeated elements, attributes, and values?
Thanks,
Deepak Shaw