Federation JVM Elide Example

This example demonstrates GraphQL Federation with Elide.

This uses Spring GraphQL to contribute a subgraph that integrates with the subgraph contributed by Elide.

Demo

1. Ensure that the Elide Spring Boot Example has GraphQL Federation enabled

elide:
  graphql:
    federation:
      enabled: true

2. Run the Elide Spring Boot Example

mvn spring-boot:run

Graphiql can be accessed at http://localhost:8080/graphiql/index.html.

3. Run the Federation JVM Elide Example

mvn spring-boot:run

Graphiql can be accessed at http://localhost:8081/graphiql?path=/graphql.

4. Ensure Rover CLI is installed

Rover is the command-line interface for managing and maintaining graphs with Apollo GraphOS.

npm install -g @apollo/rover

5. Start Rover CLI in separate consoles

Elide Spring Boot Example

rover dev --name groups --url http://localhost:8080/graphql/api

Federation JVM Elide Example

rover dev --name reviews --schema ./src/main/resources/graphql/schema.graphqls --url http://localhost:8081/graphql

6. Query Editor Access http://localhost:4000 for the query editor.

Queries

Entity Query on JVM Elide Example

The Federation JVM Elide Example extends the Group entity on the Elide Spring Boot Example with the groupReviews field.

This requires the Group on Federation JVM Elide Example to have the @key directive.

type Group @key(fields: "name") @extends {
    name: DeferredID! @external
    groupReviews: [GroupReview!]!
}

The following query is an example that starts from the Group entity on Elide Spring Boot Example.

query {
  group {
    edges {
      node {
        commonName
        groupReviews {
          stars
          text
        }
      }
    }
  }
}

The router calls Federation JVM Elide Example with the following query to add the additional fields to the Group entity.

query {
  _entities(representations: [{__typename: "Group", name: "com.yahoo.elide"}]) {
    ... on Group {
      stars
      text
    }
  }
}

The mapping for the representations to the Group is configured in the entity data fetcher in com.example.reviews.config.GraphQLConfiguration.

DataFetcher<?> entityDataFetcher = env -> {
  List<Map<String, Object>> representations = env.getArgument(_Entity.argumentName);
  return representations.stream().map(representation -> {
    // Assume only a single id key and no composite keys
    String idKey = representation.keySet().stream().filter(key -> !"__typename".equals(key)).findFirst()
        .orElse(null);
    String id = (String) representation.get(idKey);
    if (GROUP_TYPE.equals(representation.get("__typename"))) {
      return new Group(id);
    }
    return null;
  }).toList();
};

Entity Query on Elide Spring Boot Example

The Federation JVM Elide Example contains the Group entity from Elide Spring Boot Example on the GroupReview entity.

This requires the Group on Elide Spring Boot Example to have the @key directive.

The following is the schema of Group on Elide Spring Boot Example.

type Group @key(fields : "name") {
  commonName: String
  description: String
  name: DeferredID
  products(after: String, data: [ProductInput], filter: String, first: String, ids: [String], op: ElideRelationshipOp = FETCH, sort: String): ProductConnection
}

The following is the schema of GroupReview on Federation JVM Elide Example.

type GroupReview {
    id: ID!,
    text: String
    stars: Int!
    group: Group
}

The following query is an example that starts from the GroupReview entity on Federation JVM Elide Example and references the Group on Elide Spring Boot Example.

query {
  groupReviews {
    id
    stars
    text
    group {
      name
      commonName
    }
  }
}

The router calls Elide Spring Boot Example with the following query.

query {
  _entities(representations: [{__typename: "Group", name: "com.yahoo.elide"}]) {
    ... on Group {
      name
      commonName
    }
  }
}

Elide will determine the projection in GraphQLEntityProjectionMaker.

The EntitiesDataFetcher will fetch a list of NodeContainer.

public class EntitiesDataFetcher implements DataFetcher<List<NodeContainer>> {
  ...
}

The EntityTypeResolver will map the NodeContainer to the appropriate GraphQLObjectType.

Schema

Elide uses a custom scalar DeferredID instead of ID.

This needs to be registered with the Federation JVM Elide Example subgraph.

The following is the schema definition.

scalar DeferredID

The following is the Java code for the GraphQLScalarType.

public class GraphQLScalars {
  public static GraphQLScalarType DEFERRED_ID = GraphQLScalarType.newScalar().name("DeferredID")
      .description("The DeferredID scalar type represents a unique identifier.")
      .coercing(new Coercing<Object, String>() {
        @Override
        public String serialize(Object o) {
          return o.toString();
        }

        @Override
        public String parseValue(Object o) {
          return o.toString();
        }

        @Override
        public String parseLiteral(Object o) {
          if (o instanceof StringValue stringValue) {
            return stringValue.getValue();
          }
          if (o instanceof IntValue intValue) {
            return intValue.getValue().toString();
          }
          return o.toString();
        }
      }).build();
}

The following is the Java code for registering the scalar in GraphQLConfiguration.

@Bean
public GraphQlSourceBuilderCustomizer graphqlSourceBuilderCustomizer() {
  return schemaResourceBuilder -> schemaResourceBuilder
    .configureRuntimeWiring(runtimeWiring -> runtimeWiring.scalar(GraphQLScalars.DEFERRED_ID));
}