Directives

See Schema Directives for a detailed explanation about directives including examples on how to define them in the SDL and to create the required classes.

To add your custom SchemaDirectiveWiring to graphql-java-tools pass it along when creating the SchemaParser using

SchemaParser.newParser().directive("name", new MySchemaDirectiveWiring()).build()

Basic usage

Let’s say you defined a custom directive to make text uppercase in a resource schema.graphqls:

directive @uppercase on FIELD_DEFINITION

type Query {
  hello: String @uppercase
}

And the actual implementation is the following:

public class UppercaseDirective implements SchemaDirectiveWiring {
  @Override
  public GraphQLFieldDefinition onField(SchemaDirectiveWiringEnvironment<GraphQLFieldDefinition> env) {
    GraphQLFieldDefinition field = env.getElement();
    GraphQLFieldsContainer parentType = env.getFieldsContainer();

    // build a data fetcher that transforms the given value to uppercase
    DataFetcher originalFetcher = env.getCodeRegistry().getDataFetcher(parentType, field);
    DataFetcher dataFetcher =
        DataFetcherFactories.wrapDataFetcher(
            originalFetcher,
            ((dataFetchingEnvironment, value) -> {
              if (value instanceof String) {
                return ((String) value).toUpperCase();
              }
              return value;
            }));

    // now change the field definition to use the new uppercase data fetcher
    env.getCodeRegistry().dataFetcher(parentType, field, dataFetcher);
    return field;
  }
}

Add our custom directive when creating the schema parser:

SchemaParser.newParser()
  .file("schema.graphqls")
  .directive("uppercase", new UppercaseDirective())
  // ...
  .build()
  .makeExecutableSchema();

Supported locations

Support for directives is currently limited to the following locations:

• OBJECT
• FIELD_DEFINITION
• ARGUMENT_DEFINITION
• INTERFACE
• UNION
• ENUM
• ENUM_VALUE
• INPUT_OBJECT
• INPUT_FIELD_DEFINITION

Meaning directives for the following locations are currently not yet supported:

• SCALAR