Package graphql.schema

Class GraphQLArgument

  • All Implemented Interfaces:
    GraphQLDirectiveContainer, GraphQLInputSchemaElement, GraphQLInputValueDefinition, GraphQLNamedSchemaElement, GraphQLSchemaElement
    @PublicApi
public class GraphQLArgument
extends java.lang.Object
implements GraphQLNamedSchemaElement, GraphQLInputValueDefinition
    This defines an argument that can be supplied to a graphql field (via GraphQLFieldDefinition.

    Fields can be thought of as "functions" that take arguments and return a value.

    See https://graphql.org/learn/queries/#arguments for more details on the concept.

    GraphQLArgument is used in two contexts, one context is graphql queries where it represents the arguments that can be set on a field and the other is in Schema Definition Language (SDL) where it can be used to represent the argument value instances that have been supplied on a GraphQLDirective.

    The difference is the 'value' and 'defaultValue' properties. In a query argument, the 'value' is never in the GraphQLArgument object but rather in the AST direct or in the query variables map and the 'defaultValue' represents a value to use if both of these are not present. You can think of them like a descriptor of what shape an argument might have.

    However, with directives on SDL elements, the value is specified in AST only and transferred into the GraphQLArgument object and the 'defaultValue' comes instead from the directive definition elsewhere in the SDL. You can think of them as 'instances' of arguments, their shape and their specific value on that directive.

    Originally graphql-java re-used the GraphQLDirective and GraphQLArgument classes to do both purposes. This was a modelling mistake. New GraphQLAppliedDirective and GraphQLAppliedDirectiveArgument classes have been introduced to better model when a directive is applied to a schema element, as opposed to its schema definition itself.