How to extend example with scalar DateTime

[kerkhoffc]

The example easily ran on my machine.
I would like to learn how to apply the type scalar DateTime to add e.g. "lastAccessed: DateTime" to the book.
Adding "scalar DateTime" to the schema file didn't solve the exception "There is no scalar implementation for the named 'DateTime' scalar type".

How can I use DateTime in this example?

Best,
Carsten

[dondonz]

Hello, as DateTime technically isn't in the GraphQL spec, we've added it in this extended scalar library https://github.com/graphql-java/graphql-java-extended-scalars

More context in this blog post: https://www.graphql-java.com/blog/introducing-extended-scalars

[kerkhoffc]

Thank you for the quick response :-)
I checked the links and added the dependency to version 18.1 to my pom.xml.
In the schema file I added a new field issueDate: DateTime with and without additional line scalar DateTime
The trace during app-start tells me that the field type DateTime is not present.
Sorry for my blindness or wrong question - what is missing to apply DateTime scalar?

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'routerFunctionMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'graphQlRouterFunction' defined in class path resource [org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.class]: Unsatisfied dependency expressed through method 'graphQlRouterFunction' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'graphQlHttpHandler' defined in class path resource [org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.class]: Unsatisfied dependency expressed through method 'graphQlHttpHandler' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'webGraphQlHandler' defined in class path resource [org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.class]: Unsatisfied dependency expressed through method 'webGraphQlHandler' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'executionGraphQlService' defined in class path resource [org/springframework/boot/autoconfigure/graphql/GraphQlAutoConfiguration.class]: Unsatisfied dependency expressed through method 'executionGraphQlService' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'graphQlSource' defined in class path resource [org/springframework/boot/autoconfigure/graphql/GraphQlAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.graphql.execution.GraphQlSource]: Factory method 'graphQlSource' threw exception; nested exception is SchemaProblem{errors=[The field type 'DateTime' is not present when resolving type 'Book' [@7:1]]}

[dondonz]

There's only one more step - adding the DateTime scalar to the RuntimeWiring. The error message basically says, you've got a DateTime field in the schema but the GraphQL Java engine doesn't know what to do with it. Unfortunately the engine doesn't automatically pick up the DateTime scalar from the library, you'll have to register it manually.

With Spring for GraphQL, add config like this

@Configuration
public class GraphQlConfig {
    @Bean
    public RuntimeWiringConfigurer runtimeWiringConfigurer() {
        return wiringBuilder -> wiringBuilder
                .scalar(ExtendedScalars.DateTime);
    }
}

And it should work. Make sure to include scalar DateTime in your schema as well.

More info from the Spring documentation: https://docs.spring.io/spring-graphql/docs/current/reference/html/#execution-graphqlsource-runtimewiring-configurer

[kerkhoffc]

Wonderful - it works

[maurocap]

it worked here too. Thanks!

[kerkhoffc]

I understood that I then have to use datafetchers and all the stuff instead of easy access with @QueryMapping ;-)