How to invoke GraphQL api from a java spring-boot application? Is there any annotation which supports graphQL query formation?

Question

I am looking for a solution to implement an GraphQL api call from spring-boot application, having query schema as follows:

query{

getDetailsByRefNumber(RefNumbers: "")

{

field1,

field2,

field3 

} }

Does anyone have any idea how to implement this? Gone through one of the below links, but didn't find any solution

Are there any Java based Graphql client to invoke graphql server from java code?

Answer 1

You can use "graphql-webclient-spring-boot-starter" library that is available at:

https://github.com/graphql-java-kickstart/graphql-spring-webclient

<!-- https://mvnrepository.com/artifact/com.graphql-java-kickstart/graphql-webclient-spring-boot-starter -->
<dependency>
  <groupId>com.graphql-java-kickstart</groupId>
  <artifactId>graphql-webclient-spring-boot-starter</artifactId>
  <version>1.0.0</version>
</dependency>

A sample implementation can be something like this:

Assuming that you have MyEntity object:

public class MyEntity
{
    String field1;
    String field2;
    String field3;
    //getter and setters here
}

Also you have two graphql query files under "src/main/resources" folder:

query1.graphql:

#query1.graphql
#this query returns a list of some_detail_entity
query getDetailListByRefNumber($RefNumber: String!){
    some_detail_entity(where: {RefNumber : { _eq: $RefNumber } }) {
        field1
        field2
        field3 
    } 
}

query2.graphql:

#query2.graphql
#this query returns a single some_detail_entity
query getDetailByRefNumber($RefNumber: String!){
    some_detail_entity_by_pk(RefNumber : $RefNumber) {
        field1
        field2
        field3 
    } 
}

You can use this snippet to call graphql server to query & fetch some data:

ObjectMapper objectMapper = new ObjectMapper();

WebClient webClient = WebClient.builder()
.baseUrl("https://endpoint-url-of-graphql.com")//url of graphql instance
.defaultHeader("auth-token", "some-cryptic-code-if-required")//if auth header not required, just delete this line
.build();

GraphQLWebClient graphqlClient = GraphQLWebClient.newInstance(webClient, objectMapper);

//if expecting a single entity (not array)
MyObject entity = graphqlClient.post("query2.graphql", 
Map.of("RefNumber", "A7EED900-9BB4-486F-9F7C-2136E61E2278"), MyEntity.class)
            .block();   

            
//if expecting a list of entity (array)
var response = graphqlClient.post(GraphQLRequest.builder().resource("query1.graphql")
        .variables(Map.of("RefNumber", "A7EED900-9BB4-486F-9F7C-2136E61E2278")).build())
                .block();   

List<MyEntity> entityList = response.getFirstList(MyEntity.class);