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Union causes : Two different classes used for type #221
Description
Hello,
There is a bug using union with a generic Bean.
Here's a schema snipet :
In root file :
union item = Order | User
type SearchResponse {
total: Int!
items: [item]
}
extend type Query {
orders(filter: OrderFilterInput): SearchResponse
users(filter: UserFilterInput): SearchResponse
}
In java, the bean for SearchResponse is :
@DaTa
@NoArgsConstructor
@AllArgsConstructor
public class SearchResponse {
private Long total;
private List items;}
then the resolvers are :
SearchResponse users(UserFilterInput filters)
SearchResponse orders(OrderFilterInput filters)
So depending on the resolver, SearchReponse could have a List of items of type Order or User.
This rises this error:
Caused by: com.coxautodev.graphql.tools.SchemaClassScannerError: Two different classes used for type SearchResponse:
class com.api.graphql.common.core.SearchResponse:
| return type of method public com.api.graphql.common.core.SearchResponse com.api.graphql.order.OrderResolver.orders(com.api.graphql.order.OrderFilterInput)class com.api.graphql.common.core.SearchResponse:
| return type of method public com.api.graphql.common.core.SearchResponse com.api.graphql.users.UserResolver.users(com.api.graphql.users.UserFilterInput)
Can someone help me solve this please?
Activity
AdamSoufiane commentedon Feb 17, 2019
Hello,
This is the hacky solution i've found, it's dirty but it works :
@Bean public SchemaParserDictionary dictionary() { return new SchemaParserDictionary().add(MyModelClassHere.class).add(AnotherMOdelCLass.class); }all the classes involved in unions have to be added to the dictionnary.
Another possible solution is not to implement GraphQLQueryResolver but rather implement
GraphQLResolver<MyModelClassHere>. I didn't test this enough because it breaks my current code, but i'm petty sure it could work.oryan-block commentedon Oct 3, 2026
Closing as a duplicate of #343. One GraphQL type cannot be backed by several parameterizations of a generic class. Use a shared type argument (
SearchResponse<Any>or a common supertype) and add the union members to the dictionary. The broader request is tracked in #111.