sap pi rest convert xml to json

I have a stream of soap to rest

I have an xml like:

<field1> test </field1>

<field2> test2 </field1>

and I convert it to json, during the conversion I need the "records" field to be inserted as an array at the beginning, like this:

{"records": [{"field1": "test", "field2": "test2",}]}

the records field is an array, in fact after the ":" there is a [

pls help me