graphql-java SPQR:如何使用@GraphQLUnion注解？

@GraphQLUnion(name = "SearchResult", possibleTypes = {Book.class, Movie.class})
public interface SearchResultUnion {
}

public class SearchResultUnionResolver implements TypeResolver {

    @Override
    public GraphQLObjectType getType(TypeResolutionEnvironment env) {
        Object object = env.getObject();
        
        if (object instanceof Book) {
            return env.getSchema().getObjectType("Book");
        } else if (object instanceof Movie) {
            return env.getSchema().getObjectType("Movie");
        }
        
        throw new IllegalArgumentException("Unknown type: " + object.getClass());
    }
}

public class Query {

    @GraphQLQuery
    public SearchResultUnion search(String keyword) {
        // Perform search and return a Book or Movie object
    }

    @GraphQLTypeResolver(SearchResultUnionResolver.class)
    public interface SearchResultUnion {
    }
}