Federation

To enable support for GraphQL Federation, simply set the smallrye.graphql.federation.enabled config key to true.

You can add the Federation directives by using the equivalent Java annotation, e.g. to extend a Product entity with a price field, you can write a class:

package org.example.price;

import org.eclipse.microprofile.graphql.Id;

import io.smallrye.graphql.api.federation.Extends;
import io.smallrye.graphql.api.federation.Key;

@Extends @Key(fields = "id")
public class Product {
    @Id
    private String id;

    @Description("The price in cent")
    private Integer price;

    // getters and setters omitted
}

And a normal query method that takes the key fields as a parameter and returns the requested type:

package org.example.price;

import org.eclipse.microprofile.graphql.GraphQLApi;
import org.eclipse.microprofile.graphql.Id;
import org.eclipse.microprofile.graphql.Query;

@GraphQLApi
public class Prices {
    @Query
    public Product product(@Id String id) {
        return ...;
    }
}

The GraphQL Schema then contains:

type Product @extends @key(fields : ["id"]) {
    id: ID
    price: Int
}

union _Entity = Product

type Query {
    _entities(representations: [_Any!]!): [_Entity]!
    _service: _Service!
    product(id: ID): Product
}