The documentation for graphql-java-annotations doesn't do such a great job of telling me how to add a Custom Scalar to my schema: https://github.com/Enigmatis/graphql-java-annotations/tree/v8.0.1#annotations-schema-creator
What I need is to create some 'scalar Date' in the Schema. It is unclear how to do this with the AnnotationsSchemaCreator builder thing.
GraphQLSchema schema = AnnotationsSchemaCreator.newAnnotationsSchema()
.query(Query.class) // to create you query object
.mutation(Mutation.class) // to create your mutation object
.subscription(Subscription.class) // to create your subscription object
.directive(UpperDirective.class) // to create a directive
.additionalType(AdditionalType.class) // to create some additional type and add it to the schema
.typeFunction(CustomType.class) // to add a typefunction
.setAlwaysPrettify(true) // to set the global prettifier of field names (removes get/set/is prefixes from names)
.setRelay(customRelay) // to add a custom relay object
.build();
The docs give me just that. Is a typeFunction what I need here? Do I have to first get the graphql-java "Custom Scalar" stuff set up and put that into the typeFunction?
What's happening right now is that my graphql-java-annotations Types which need the Date type...
public abstract class BasePart {
@GraphQLField
@GraphQLNonNull
@JsonIgnore
public String id;
...
@GraphQLField
public Date createdOn;
...
}
Get into the Schema without the Date scalar defined so the GraphiQL UI is rejecting it with errors like...
Error: Date fields must be an object with field names as keys or a function which returns such an object.
at invariant (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:13:12678)
at defineFieldMap (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:14:16395)
at e.getFields (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:14:22028)
at http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:22055
at typeMapReducer (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:22227)
at http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:22200
at Array.forEach (<anonymous>)
at http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:22082
at typeMapReducer (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:22227)
at typeMapReducer (http://localhost.blueorigin.com:8080/webjars/graphiql/0.10.1/graphiql.min.js:15:21564)
I'm trying to figure out how to get that information into the, what, AnnotationsSchemaCreator.newAnnotationsSchema() builder?
How do you add a Custom Scalar to a graphql-java-annotations project?
The TypeFunction is the key. You pass the TypeFunction when you are building the Schema with the AnnotationsSchemaCreator. The following code effectively got scalar Date into the service's GraphQL Schema
graphQLSchema = AnnotationsSchemaCreator.newAnnotationsSchema()
.query(QuerySchema.class)
.setAlwaysPrettify(true)
.typeFunction(new MyDateTypeFunction()) // <-- This got scalar Date onto the schema
.build();
The TypeFunction itself realizes the support for the scalar Date.
public class MyDateTypeFunction implements TypeFunction {
@Override
public boolean canBuildType(Class<?> clazz, AnnotatedType annotatedType) {
return clazz == java.util.Date.class;
}
@Override
public GraphQLType buildType(
boolean b,
Class<?> clazz,
AnnotatedType annotatedType,
ProcessingElementsContainer processingElementsContainer) {
return MY_DATE;
}
public static final GraphQLScalarType MY_DATE = GraphQLScalarType
.newScalar()
.name("Date")
.description("Coerce java.util.Date to/from a String representation of the long value of getTime().")
.coercing(
new Coercing() {
@Override
public Object serialize(Object dataFetcherResult) throws CoercingSerializeException {
if (dataFetcherResult instanceof Date) {
final String result = String.format("%d", ((Date) dataFetcherResult).getTime());
return result;
}
final String message =
String.format("Expected type java.util.Date but found %s", typeName(dataFetcherResult));
throw new CoercingSerializeException(message);
}
@Override
public Object parseValue(Object input) throws CoercingParseValueException {
if (input instanceof String) {
try {
return stringToDate((String) input);
} catch (NumberFormatException nfe) {
final String message = String.format("NumberFormatException %s", nfe.getMessage());
throw new CoercingParseValueException(message);
}
}
final String message = String.format("Unable to parseValue %s to a java.util.Date", input);
throw new CoercingParseValueException(message);
}
@Override
public Object parseLiteral(Object input) throws CoercingParseLiteralException {
if (input instanceof StringValue) {
try {
final String inputStringValue = ((StringValue) input).getValue();
return stringToDate(inputStringValue);
} catch (NumberFormatException nfe) {
final String message = String.format("NumberFormatException %s", nfe.getMessage());
throw new CoercingParseLiteralException(message);
}
}
final String message = String.format("Unable to parseLiteral %s to a java.util.Date", input);
throw new CoercingParseLiteralException(message);
}
}
)
.build();
public static Date stringToDate(String input) throws NumberFormatException {
final long inputAsLong = Long.parseLong(input);
return new Date(inputAsLong);
}
public static String typeName(Object input) {
return input == null ? "null" : input.getClass().getName();
}
}
Note that I'm not recommending that you represent java.util.Date as the String value of the long getTime(), java.time.Instant's ISO-8601 is so much more readable, but my service needed this string value and this is how I got it into a graphql-java-annotation's project schema.