Reflectively save domain class instances in Grails - json

Question

The problem is as follows: I want to handle a POST request with JSON body. The body consists of an array of JSON Objects, without further nesting, i.e. simple HashMaps. All of these objects represent JSON-serialized domain classes from an Android Application, which will have their counterpart in my Grails app. I am thinking of parsing the JSON body, iterating through every element and saving each node as its corresponding domain class instance.
a) How should I save the instance? I am quite new to Grails/Groovy so please excuse any huge mistakes. Code so far is
public static Object JSONArray2Instances(String json, Class type) {
def slurper = new JsonSlurper()
def result = slurper.parseText(json)
//we only want to parse JSON Arrays
if (!(result instanceof JSONArray))
return null
result.each {
def instance = it.asType(type)
// now I need to save to domain class!
}
}
b) where do I place the corresponding code? Currently it is in /grails-app/src/groovy. Where do the tests go? (Since it is not a 'real' Grails component)
c) Is an intermediate command object more appropriate?

Answer 1

Your code should go in to the controller which is handling the request. Please take a look at
gson-grails plugin which has examples of how to serialize and deserialze objects and map them to domain objects. Please take a look at the grails basics where they talk about the conventions used in the grails application and the layout. There are good examples at grails site. Hope this helps

Answer 2

I solved my problem as follows, based on help provided by the comment from allthenutsandbolts. : (Grails-Gson plugin was not needed)
Let N2696AdminAction be the name of a Domain Class
in my controller:
class N2696AdminActionController extends RestfulController{
static responseFormats = ['json', 'xml']
def JSONHandlerService
N2696AdminActionController() {
super(N2696AdminAction)
}
#Override
#Transactional
def save(){
if (request!=null)
JSONHandlerService.instancesfromJSON(request.JSON)
}
}
then I delegate persisting to my service as follows
class JSONHandlerService {
def instancesfromJSON(Object request){
//we only want to parse JSON Arrays
if (!(request instanceof JSONArray))
return null
request.each {
def domainClass = Class.forName("${it.type}",
true, Thread.currentThread().getContextClassLoader())
def newDomainObject = domainClass.newInstance(it)
newDomainObject.save(failOnError:true, flush:true, insert: true)
}
}
}
type is a Json attribute which holds the full (package inclusive) name for my class. This way, I can save to multiple Domain Classes with the same POST request.