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https://issues.apache.org/jira/browse/SLING-9796?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bertrand Delacretaz closed SLING-9796.
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> Add support for using Unions
> ----------------------------
>
> Key: SLING-9796
> URL: https://issues.apache.org/jira/browse/SLING-9796
> Project: Sling
> Issue Type: New Feature
> Components: GraphQL
> Reporter: Adrian Kozma
> Assignee: Radu Cotescu
> Priority: Major
> Fix For: GraphQL Core 0.0.8
>
>
> (i) The current implementation of *sling-org-apache-sling-graphql-core* is
> not supporting the *Union* type, however there's a way to implement it.
> 1. Hardcoded solution just to prove what is missing.
> Supporting *Unions* can be added by extending the *buildWiring()* method [3]
> adding the following lines
> - based on the graphql-java documentation [4] the TypeResolver returns the
> schema ObjectType based on the current result item instance
> {code:java}
> List<UnionTypeDefinition> unionTypes =
> typeRegistry.getTypes(UnionTypeDefinition.class);
> for (UnionTypeDefinition type : unionTypes) {
> TypeResolver typeResolver = env -> {
> Object javaObject = env.getObject();
> // schema contains only one union definition:
> // "union TestUnion = Type_1 | Type_2 | Type_3 | Type_4"
> // hardcoding to force return the object type Type1
> return env.getSchema().getObjectType("Type1");
> };
> builder.type(type.getName(), typeWriting ->
> typeWriting.typeResolver(typeResolver));
> }
> {code}
> 2. General solution
> The suggested solution would be to extend
> *sling-org-apache-sling-graphql-core* to allow TypeProviders as external
> callable, following the pattern how it was implemented in case of data
> fetchers.
> Unfortunately, there's no general logic (in sling) regarding how a
> TypeProvider can decide which Object Type needs to be returned. The condition
> is based on the result item (javaObject) which is constructed by the data
> fetcher (external callable). Therefore, to match the logic, the TypeResolver
> should be callable (OSGI component) which could be detected by directives
> (@fecher) used by the Union type definition as follows:
> {code:java}
> # This directive maps the corresponding type resolver to a given Union
> directive @resolver(
> name: String,
> options: String = "",
> source: String = ""
> ) on UNION
> union TestUnion @resolver(name : "test/resolver", source : "TestUnion") =
> Type_1 | Type_2 | Type_3 | Type_4{code}
> [3]
> [https://github.com/apache/sling-org-apache-sling-graphql-core/blob/19bc07c039bfb3e9d578e9c592b60c3da6bdd951/src/main/java/org/apache/sling/graphql/core/engine/GraphQLResourceQuery.java#L133]
> [4]
> [https://www.graphql-java.com/documentation/v11/schema/#datafetcher-and-typeresolver]
>
>
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