Best practice to map REST query params to DGS

[owengalenjones]

Hello, I am evaluating a few different GraphQL implementations that would sit in front of an existing REST service and am having some uncertainty as to how to best accomplish something specific.

As an example our REST service exposes say:

GET /foos
GET /foo/{id}

and both of those support a query param:

GET /foos?selector=bar,baz
GET /foo/{id}?selector=bar,baz

In GraphQL I would like to treat bar,baz as fields which have their own fields:

query Foo {
    Foo(id: "974cf6b9-ab84-4276-9284-91f01e1dbe92") {
        id
        name
        size
        bar {
            id
            name
        }
        baz {
          etag
        }
    }
}

The inclusion of bar and baz result in the service making separate requests to fetch the data and so are skipped if the the request lacks the respective ?selector query param. I'm not sure how to map this to DGS.

I have a FooDataFetcher that talks to a FooService. Following the example for child data it would in this case would result in code like:

Foo foo = dfe.getSource();
barService.forFoo(foo.getId());
bazService.forFoo(foo.getId());

which would result in three separate REST queries:

GET /foo/1
GET /foo/1?selector=bar
GET /foo/1?selector=baz

which I would like to avoid.

I'm guessing that somehow this problem would be best solved through the use of a DataLoader where it would accumulate:

• request for Foo with id=1
• request for Foo with id=1 and selector=bar
• request for Foo with id=1 and selector=baz

which gets resolve to a single request:

GET /foo/1?selector=bar,baz

But I'm not sure if I'm on the right track with this thinking and can't find supporting cases in the examples. Thank you for any assistance.