Categories
grails grails-domain-class json

Grails get child domain objects

I have two domain classes one is parent and other one is child and i have a hasMany relationship between them. Parent class has many childs and child class belongs to parent class.
And here is coding example.

class Parent{
String name
static hasMany = [childs:Child]
static constraints = {
}
}
class Child{
String name
static belongsTo = [parent:Parent]
static constraints={}
}

Problem is as soon as I get the parent object the child objects associated with parent class were also fetched. But when I convert the object to JSON I don’t see the child object completely I can only able to see the ID’s of child objects. I want to see all columns of child object instead of only Id.

Converted JSON response:

[{"class":"project.Parent","id":1,
"name":"name1","childs":[{"class":"Child","id":1},{"class":"Review","id":2}]}]

But I want the response which contains name of child object too, as follows

[{"class":"project.Parent","id":1,"name":"name1",
"childs":[{"class":"Child","id":1,"name":"childname1"},
{"class":"Review","id":2,"name":"childname2"}
]
}]

Any help greatly appreciated.
Thanks in advance.

The issue is with the use of default JSON converter. Here are your options:

 1. Default  -  all fields, shallow associations
a. render blah as JSON
2. Global deep converter - change all JSON converters to use deep association traversal
a. grails.converters.json.default.deep = true
3. Named config marshaller using provided or custom converters
a. JSON.createNamedConfig('deep'){
it.registerObjectMarshaller( new DeepDomainClassMarshaller(...) )
}
b. JSON.use('deep'){
render blah as JSON
}
4. Custom Class specific closure marshaller
a. JSON.registerObjectMarshaller(MyClass){ return map of properties}
b. render myClassInstance as JSON
5. Custom controller based closure to generate a map of properties
a. convert(object){
return map of properties
}
b. render convert(blah) as JSON

You are currently using Option 1, which is default.

The simplest you can do is use Option 2 to set global deep converter, but be aware this effects ALL domain classes in your app. Which means that if you have a large tree of associations culminating in a top level object and you try to convert a list of those top level objects the deep converter will execute all of the queries to fetch all of the associated objects and their associated objects in turn. – You could load an entire database in one shot 🙂 Be careful.