GraphQL

GraphQL is a query language for your API.

Say API return 100 fields in a response , we have various client and each client need different fileds in their response, then GraphQL describe those need and return those only fileds as a response.

Client just need to describe which field they need, GraphQL will take care of that.

need to create schema file for gaphql as below in graphql folder.

schema.graphql

==

type Product{

id: ID,

name:String

category:String

price:Float

stock:Int

}

type Query{

getProducts:[Product]

getProductsByCategory(category:String):[Product]

}

type Mutation{

updateStock(id:ID,stock:Int):Product

receiveNewShipment(id:ID,quantity:Int):Product

}

application.properties

#Enabling GraphQL playground

spring.graphql.graphiql.enabled=true

spring.graphql.graphiql.path=/graphiql

Replace RestController with only Controller , GetMapping with QuryMapping, PostMapping with MutationMapping

@Controller

public class ProductController {

@Autowired

private ProductService service;

@QueryMapping/fetch/retireve operation

public List<Product> getProducts() {

return service.getProducts();

}

@QueryMapping//fetch/retireve operation

public List<Product> getProductsByCategory(@Argument String category) {

return service.getProductsByCategory(category);

}

@MutationMapping//for update/delete operation

public Product updateStock(@Argument int id, @Argument int stock) {

return service.updateStock(id, stock);

}

@MutationMapping//for update/delete operation

@SubscriptionMapping

public Product receiveNewShipment(@Argument int id, @Argument int quantity) {

return service.receiveNewShipment(id, quantity);

}

}

How to consume GraphQL service with graphql client

==

As a part of configuration, get graphqlclient bean as below

@Configuration

public class GraphQLClientConfig {

@Bean

public HttpGraphQlClient graphQlClient() {

WebClient webClient = WebClient.builder()

.baseUrl("http://localhost:9191/graphql")

.build();

return HttpGraphQlClient.builder(webClient).build();

}

}

let us write a client class

==

@Component

public class InventoryClient {

@Autowired

private HttpGraphQlClient graphQlClient;

public List<Item> viewProducts() {

String graphQLQuery = "query GetProducts {\n" +

" getProducts {\n" +

" name\n" +

" price\n" +

" }\n" +

"}";

return graphQlClient.document(graphQLQuery)

.retrieve("getProducts")

.toEntityList(Item.class).block();

}

public List<Item> viewProductsByCategory(String category) {

String graphQLQuery = String.format("query GetProductsByCategory {\n" +

" getProductsByCategory(category: \"%s\") {\n" +

" name\n" +

" category\n" +

" price\n" +

" stock\n" +

" }\n" +

"}\n", category);

return graphQlClient.document(graphQLQuery)

.retrieve("getProductsByCategory")

.toEntityList(Item.class).block();

}

public Item receiveNewShipment(ItemRequestDTO itemRequest) {

String graphQlQuery = String.format("mutation ReceiveNewShipment {\n" +

" receiveNewShipment(id: \"%s\", quantity: %d) {\n" +

" name\n" +

" price\n" +

" stock\n" +

" }\n" +

"}\n", itemRequest.getId(), itemRequest.getQty());

return graphQlClient.document(graphQlQuery)

.retrieve("receiveNewShipment")

.toEntity(Item.class).block();

}

}