FieldValidationInstrumentation.java

@Autowired
public GraphQlSampleController(final GraphQLRuleService ruleService) {

  // Schema generated from query classes
  GraphQLSchema schemaFromAnnotated = new GraphQLSchemaGenerator()//
      // setup the schema
      // ...
      .generate();

  // set up field validation
  CustomFieldValidation fieldValidation = new CustomFieldValidation();
  fieldValidation
      // add rules for when user is registering
      .addRules(ExecutionPath.parse("/userRegister"), UserRegisterRequest.getRules(ruleService))
  ;

  FieldValidationInstrumentation instrumentation = new FieldValidationInstrumentation(fieldValidation);

  // add rules to the schema
  graphQlFromAnnotated = GraphQL.newGraphQL(schemaFromAnnotated)//
      .instrumentation(instrumentation)//
      .build();

  LOGGER.info("Generated GraphQL schema using SPQR");
}