Adrian Kozma created SLING-9796:
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Summary: GraphQL 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
Affects Versions: GraphQL Core 0.0.8
Reporter: Adrian Kozma
(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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