How to update a row (grails domain class) based on id?

Question

I need to update a row in DB whose id is known. But the number of fields to update is high and is a complex object. (ie) contains nested objects. Hence I am trying the below lines of code, but instead of update an insert happens

long myId // Primary key/id of row to be updated
DomainObject obj = gson.fromJson(jsonString, DomainObject.class)
obj.id=myId
obj.save(flush:true)

Please help why it doing insert instead of update. How to update a row (grails domain class) based on id ?

Answer 1

You can try this.

        def gson = gsonBuilder.create()
        // because the incoming JSON contains an id this will read the DomainObject
        // from the database and update it!
        def domainObjectInstance = gson.fromJson(request.reader, DomainObject)

        domainObjectInstance.save();

Answer 2

Try updating your original object from DB with json attributes

long myId = 1
//load from DB
def o1 = DomainObject.get(myId) 
//create object from json (or just create Map)
def o2 = gson.fromJson(jsonString, DomainObject)
//set all properties from json into object from DB
o2.properties.each { updateKey, updateValue ->
    o1[updateKey] = updateValue
}
//save your original object to DB with new attributes
o1.save()