AEM does not support exposing a SOAP based web service (you can consume a 3rd party SOAP web service - not expose one).
However - you can write an AEM Sling Servlet that then you can invoke it using REST requests. For example - a GET. Now for working with JSON in AEM, You can write a Sling Servlet and use JSON libs - such as the Simple JSON lib:
https://code.google.com/p/json-simple/
THis shows invoking a sling servlet from an AEM page - but you can invoke from outside of AEM too and the servlet returns the JSON data.
To learn how to write a SLing Servlet that uses the simple JSON (including how to bundle that into an OSGi) -- see this community article:
https://helpx.adobe.com/experience-manager/using/custom-sling-servlets.html
PS - you placed this thread in the communites forum (meant for AEM Communities questions) - next time - please place AEM related questions in the main AEM forum.
