Federation _ Spring for GraphQL1.3.2中文文档(官方文档中文翻译)|Spring 教程 —

Spring for GraphQL provides an integration for the federation-jvm library, which uses GraphQL Java to initialize the schema of a sub-graph within a graph of federated services. See Apollo Federation and the Subgraph specification for details.spring-doc.cn

Config

To enable the integration, declare a FederationSchemaFactory bean in your config, and plug it into GraphQlSource.Builder. For example, with Spring Boot:spring-doc.cn

@Configuration
public class FederationConfig {

	@Bean
	public GraphQlSourceBuilderCustomizer customizer(FederationSchemaFactory factory) {
		return builder -> builder.schemaFactory(factory::createGraphQLSchema);
	}

	@Bean
	public FederationSchemaFactory schemaFactory() {
		return new FederationSchemaFactory();
	}
}

Now the schema for the sub-graph service can extend federated types:spring-doc.cn

type Book @key(fields: "id") @extends {
    id: ID! @external
    author: Author
}

type Author {
    id: ID
    firstName: String
    lastName: String
}

`@EntityMapping`

An @EntityMapping method can load federated type instances in response to an _entities query from the federation gateway. For example:spring-doc.cn

For example:spring-doc.cn

@Controller
private static class BookController {

	@EntityMapping
	public Book book(@Argument int id) { (1)
		// ...
	}

	@SchemaMapping
	public Author author(Book book) { (2)
		// ...
	}

}

1	The `@Argument` method parameter is resolved from the "representation" input map for the entity. The full "representation" input `Map` can also be resolved. See Method Signature for supported method argument and return value types.
2	`@SchemaMapping` methods can be used for the rest of the graph.

An @EntityMapping method can batch load federated entities of a given type. To do that, declare the @Argument method parameter as a list, and return the corresponding entity instances as a list in the same order.spring-doc.cn

For example:spring-doc.cn

@Controller
private static class BookController {

	@EntityMapping
	public List<Book> book(@Argument List<Integer> idList) { (1)
		// ... return books in the same order
	}

	@BatchMapping
	public Map<Book, Author> author(List<Book> books) { (2)
		// ...
	}
}

1	The `idList` naming convention helps to de-pluralize the parameter name in order to look up the correct value in the "representation" input map. You can also set the argument name through the annotation.
2	`@BatchMapping` methods can be used for the rest of the graph.

Method Signature

Entity mapping methods support the following arguments:spring-doc.cn

Method Argument Description

Method Argument	Description
`@Argument`spring-doc.cn	For access to a named value from the "representation" input map, also converted to typed Object.spring-doc.cn
`Map<String, Object>`spring-doc.cn	The full "representation" input map for the entity.spring-doc.cn
`List<Map<String, Object>>`spring-doc.cn	The list of "representation" input maps when using a single controller method to load all entities of a given type.spring-doc.cn
`@ContextValue`spring-doc.cn	For access to an attribute from the main `GraphQLContext` in `DataFetchingEnvironment`.spring-doc.cn
`@LocalContextValue`spring-doc.cn	For access to an attribute from the local `GraphQLContext` in `DataFetchingEnvironment`.spring-doc.cn
`GraphQLContext`spring-doc.cn	For access to the context from the `DataFetchingEnvironment`.spring-doc.cn
`java.security.Principal`spring-doc.cn	Obtained from the Spring Security context, if available.spring-doc.cn
`@AuthenticationPrincipal`spring-doc.cn	For access to `Authentication#getPrincipal()` from the Spring Security context.spring-doc.cn
`DataFetchingFieldSelectionSet`spring-doc.cn	For access to the selection set for the query through the `DataFetchingEnvironment`.spring-doc.cn
`Locale`, `Optional<Locale>`spring-doc.cn	For access to the `Locale` from the `DataFetchingEnvironment`.spring-doc.cn
`DataFetchingEnvironment`spring-doc.cn	For direct access to the underlying `DataFetchingEnvironment`.spring-doc.cn

@Argumentspring-doc.cn

For access to a named value from the "representation" input map, also converted to typed Object.spring-doc.cn

Map<String, Object>spring-doc.cn

The full "representation" input map for the entity.spring-doc.cn

List<Map<String, Object>>spring-doc.cn

The list of "representation" input maps when using a single controller method to load all entities of a given type.spring-doc.cn

@ContextValuespring-doc.cn

For access to an attribute from the main GraphQLContext in DataFetchingEnvironment.spring-doc.cn

@LocalContextValuespring-doc.cn

For access to an attribute from the local GraphQLContext in DataFetchingEnvironment.spring-doc.cn

GraphQLContextspring-doc.cn

For access to the context from the DataFetchingEnvironment.spring-doc.cn

java.security.Principalspring-doc.cn

Obtained from the Spring Security context, if available.spring-doc.cn

@AuthenticationPrincipalspring-doc.cn

For access to Authentication#getPrincipal() from the Spring Security context.spring-doc.cn

DataFetchingFieldSelectionSetspring-doc.cn

For access to the selection set for the query through the DataFetchingEnvironment.spring-doc.cn

Locale, Optional<Locale>spring-doc.cn

For access to the Locale from the DataFetchingEnvironment.spring-doc.cn

DataFetchingEnvironmentspring-doc.cn

For direct access to the underlying DataFetchingEnvironment.spring-doc.cn

@EntityMapping methods can return Mono, CompletableFuture, Callable, or the actual entity.spring-doc.cn

Exception Handling

You can use @GraphQlExceptionHandler methods to map exceptions from @EntityMapping methods to GraphQLError's. The errors will be included in the response of the "_entities" query. Exception handler methods can be in the same controller or in an @ControllerAdvice class.spring-doc.cn

1	The `@Argument` method parameter is resolved from the "representation" input map for the entity. The full "representation" input `Map` can also be resolved. See Method Signature for supported method argument and return value types.
2	`@SchemaMapping` methods can be used for the rest of the graph.

1	The `idList` naming convention helps to de-pluralize the parameter name in order to look up the correct value in the "representation" input map. You can also set the argument name through the annotation.
2	`@BatchMapping` methods can be used for the rest of the graph.