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The Helidon GraphQL Server provides a framework for creating GraphQL applications that integrate with the Helidon WebServer. GraphQL is a query language to access server data. The Helidon GraphQL integration enables HTTP clients to issue queries over the network and retrieve data; it is an alternative to other protocols such as REST or GRPC.

To enable GraphQL add the following dependency to your project’s pom.xml (see Managing Dependencies).

<dependency>
    <groupId>io.helidon.graphql</groupId>
    <artifactId>helidon-graphql-server</artifactId>
</dependency>

An instance of GraphQlSupport must be registered in the Helidon WebServer routes to enable GraphQL support in your application. In addition, a GraphQL schema needs to be specified to verify and execute queries.

The following code fragment creates an instance of GraphQlSupport and registers it in the Helidon WebServer.

    WebServer server = WebServer.builder()
            .routing(Routing.builder()
                            .register(GraphQlSupport.create(buildSchema()))
                            .build())
            .build();

By default, GraphQlSupport will reserve /graphql as the URI path to process queries. The buildSchema method creates the schema and defines 2 types of queries for this application:

private static GraphQLSchema buildSchema() {
    String schema = "type Query{\n"    
            + "hello: String \n"
            + "helloInDifferentLanguages: [String] \n"
            + "\n}";

    SchemaParser schemaParser = new SchemaParser();
    TypeDefinitionRegistry typeDefinitionRegistry = schemaParser.parse(schema);

    // DataFetcher to return various hellos in difference languages  
    DataFetcher<List<String>> hellosDataFetcher = (DataFetcher<List<String>>) environment ->
            List.of("Bonjour", "Hola", "Zdravstvuyte", "Nǐn hǎo", "Salve", "Gudday",
                    "Konnichiwa", "Guten Tag");

    RuntimeWiring runtimeWiring = RuntimeWiring.newRuntimeWiring()  
            .type("Query", builder -> builder.dataFetcher("hello", new StaticDataFetcher("world")))
            .type("Query", builder -> builder.dataFetcher("helloInDifferentLanguages", hellosDataFetcher))
            .build();

    SchemaGenerator schemaGenerator = new SchemaGenerator();
    return schemaGenerator.makeExecutableSchema(typeDefinitionRegistry, runtimeWiring);  
}

The following is a description of each of these steps:

• Define the GraphQL schema.
• Create a DataFetcher to return a list of hellos in different languages.
• Wire up the DataFetcher s.
• Generate the GraphQL schema.

The following configuration keys can be used to set up integration with WebServer:

The following configuration keys can be used to set up GraphQL invocation:

Using the schema defined in Section , you can probe the following endpoints:

1. Hello world endpoint

   curl -X POST http://127.0.0.1:PORT/graphql -d '{"query":"query { hello }"}'
   
   "data":{"hello":"world"}}

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2. Hello in different languages

   curl -X POST http://127.0.0.1:PORT/graphql -d '{"query":"query { helloInDifferentLanguages }"}'
   
   {"data":{"helloInDifferentLanguages":["Bonjour","Hola","Zdravstvuyte","Nǐn hǎo","Salve","Gudday","Konnichiwa","Guten Tag"]}}

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• GraphQL Javadocs