Custom serialization of specific return type for DataFetcher

Question

I am using Spring for GraphQL (version 2.7.0-M1).

In my domain model, a lot of properties return an object Foo. This object must be serialized to a String based on data available from GraphQlContext. So the schema looks like:

  type Parent {
      code: String!
      foo: String
      ...
  }
  

It is easy to do this with @SchemaMapping for a specific parent type.

@SchemaMapping(typeName = "Parent", field = "foo")
public String foo(Parent parent, DataFetchingEnvironment env) {
    var context = env.getGraphQlContext();
    return ... 
    

However, this is not very DRY. I am looking for a way to have this code at one place, like a custom scalar. Is there a way to do this with spring-graphql / graphql-java?

Example

An example is a Localized<T> object we use. For instance a Product instance has Localized<String> properties for title and description (and more). For the GraphQL query we can set the context, part of the context is the Locale. For all Localized property values the value can be converted to the string value for the locale. We are looking for a way to do this automagically. Otherwise it creates a lot of boiler plate code

Answer 1

Would @ContextValue help here? This would remove a bit of boilerplate from your controller handlers.

@SchemaMapping(typeName = "Parent", field = "foo")
public String foo(Parent parent, @ContextValue Foo foo) {

If you'd like something more involved, I think you should elaborate on the exact relationship between an attribute of one or multiple types in your schema, and some random value in the context.

Maybe you could come up with some concrete example here?