Custom Scalar in Graphql-java

Question

We are planning use Graphql as backend server in our application. We choose Graphql-Java to develop our POC. We came across a stituation to create our own scalartype to han

Answer 1

To get a general idea how to make a scalar, just take a look into the existing ones and do something similar.

graphql-java also has a separate project for extra scalars: graphql-java-extended-scalars. And there you can find the object scalar (a.k.a. JSON scalar), that can be used for dynamic structures, like Maps.

Register it via:

RuntimeWiring.newRuntimeWiring().scalar(ExtendedScalars.Object)

Answer 2

In code first approach (SPQR v0.9.6) adding @GraphQLScalar is enough. Or, as alternative, add scalar definition to GraphQLSchemaGenerator:

new GraphQLSchemaGenerator()
.withScalarMappingStrategy(new MyScalarStrategy())

And define MyScalarStrategy:

class MyScalarStrategy extends DefaultScalarStrategy {

@Override
public boolean supports(AnnotatedType type) {
  return super.supports(type) || GenericTypeReflector.isSuperType(MyScalarStrategy.class, type.getType());
}
}