Springdocs: Specifying an explicit type for Paged responses - spring-boot

Question

I'm working on a "global search" for my application.
Currently, I'm using hibernate-search to search for instances of multiple different objects and return them to the user.
The relevant code looks as follows:
Search.session(entityManager)
.search(ModelA.classs, ModelB.class)
.where(...)
.sort(...)
.fetch(skip, count);
Skip and count are calculated based on a Pageable and the result is used to create an instance of Page, which will be returned to the controller.
This works as I'd expect, however, the types generated by swagger-docs obviously doesn't know, what the type within the Page is, and therefore uses Object.
I'd like to expose the correct types, as I use them to generate the types for the frontend application.
I was able to set the type to an array, when overwriting the schema like this:
#ArraySchema(schema = #Schema(anyOf = {ModelA.class, ModelB.class}))
public Page<?> search(Pageable pageable) {
However, this just disregards the Page and also isn't correct.
The next thing I tried is extending the PageImpl, overwriting the getContent method, and specifying the same schema on this method, but this wasn't included in the output at all.
Next was implementing Page<T> myself (and later removing the implements reference to Page<T>) and specifying the same schema on getContent, iterator, and the field itself, but also to no effect.
How do I tell spring-docs, what the content of the resulting Page might be?

Answer 1

I stumbled upon this when trying to solve a similar problem
Inspired from this thread Springdoc with a generic return type i came up with the following solution, and it seems to apply to your case also. Code examples are in Kotlin.
I introduced a stub class that will just act as the Schema for the response:
private class PageModel(
#Schema(oneOf = [ModelA::class, ModelB::class]))
content: List<Object>
): PageImpl<Object>(content)
Then i annotated my Controller like this:
#Operation(
responses = [
ApiResponse(
responseCode = "200",
content = [Content(schema = Schema(implementation = PageModel::class))]
)
]
)
fun getPage(pageable: Pageable): Page<Object>
This generated this api response:
"PageModel": {
"properties": {
"content": {
"items": {
"oneOf": [
{
"$ref": "#/components/schemas/ModelA"
},
{
"$ref": "#/components/schemas/ModelB"
}
],
"type": "object"
},
"type": "array"
},
... -> more page stuff from spring's PageImpl<>
And in the "responses" section for the api call:
"responses": {
"200": {
"content": {
"application/json": {
"schema": {
"$ref": "#/components/schemas/PageModel"
}
}
},
"description": "OK"
}
All generated openapi doc is similar to the autogenerated json when returning a Page, it just rewrites the "content" array property to have a specific type.