The schema defined in the content of RequestBody ignores the setting of discriminator

[lawli]

It seems in the method of getSchemaFromAnnotation in AnnotationsUtils, it does not consider copying discriminatorProperty and discriminatorMapping.

[bnasslahsen]

Can you please add more details about your request :

• What modules of springdoc-openapi are you using?
• Provide with a sample code of HelloController to reproduce it?
• What is the actual result using OpenAPI Description (yml or json)?
• What is the expected result using OpenAPI Description (yml or json)?

Thank you in advance.

[lawli]

I am using the following annotation in the code

@operation(
description = "Sample",
requestBody = @io.swagger.v3.oas.annotations.parameters.RequestBody(
content = @content(schema = @Schema(
oneOf = {Debit.class, Credit.class},
discriminatorProperty = "transactionType",
discriminatorMapping = {
@DiscriminatorMapping(value = "DEBIT", schema = Debit.class),
@DiscriminatorMapping(value = "CREDIT", schema = Credit.class)
}
))
)
)

The expect result is

"requestBody": {
"content": {
"application/json": {
"schema": {
"discriminator": {
"propertyName": "transactionType",
"mapping": {
"DEBIT": "#/components/schemas/Debit",
"CREDIT": "#/components/schemas/Credit"
}
},
"oneOf": [
{
"$ref": "#/components/schemas/Debit"
},
{
"$ref": "#/components/schemas/Credit"
}
]
}
}
}
}

But the actual result is

"requestBody": {
"content": {
"application/json": {
"schema": {
"oneOf": [
{
"$ref": "#/components/schemas/Debit"
},
{
"$ref": "#/components/schemas/Credit"
}
]
}
}
}
}

While I debug into the code, the requestbody is constructed in org.springdoc.core.RequestBodyBuilder and the Schema of the Content is extracted from method getSchemaFromAnnotation in class io.swagger.v3.core.util.AnnotationsUtils

[bnasslahsen]

Hi @lawli,

As you have described, this behaviour is mainly related to swagger-api.
The main root cause issue, is the following:

• Composed Model For swagger 2.0 needs to include field discriminator field swagger-api/swagger-core#3421

You can look at the sample how to generate the discriminator in the documentation.
Your @Schema annotation, just needs to be added on the superclass.

The following issue, contains an example of how to get the discriminator in the documentation:

• Composition/Inheritance/Polymorphism issues (v2.0.6) swagger-api/swagger-core#3046

[lawli]

I don't think it is the problem of swagger-api. If I populate the ComposedSchema manually, it shows the expected result.

public OpenApiCustomiser apiCustomerser() {
    return openApi -> {
        MediaType md = new MediaType();
        Discriminator ds = new Discriminator();
        ds.setPropertyName("transactionType");
        ds.mapping("DEBIT", "#/components/schemas/Debit");
        ds.mapping("CREDIT", "#/components/schemas/Credit");
        ComposedSchema sc = new ComposedSchema();
        List oneOf = Arrays.asList(
                new Schema().$ref("#/components/schemas/Debit"),
                new Schema().$ref("#/components/schemas/Credit")
        );
        sc.setOneOf(oneOf);
        sc.setDiscriminator(ds);
        md.schema(sc);

        openApi.getPaths().entrySet().stream()
                .flatMap(entry -> entry.getValue().readOperations().stream())
                .forEach(op -> op.getRequestBody().getContent().addMediaType("application/json", md));
    };
}

[bnasslahsen]

Using the OpenApiCustomiser shoud be the silver bullet and the last solution to choose:

Your requirement looks quite standard and doesn't require any customisations.
When you use OpenApiCustomiser, then you are not using the native swagger-api annotations.

As mentioned, you can simply add the @Schema declaration on your class (and not on the @RequestBody) as proposed on swagger-api/swagger-core#3046. This is a safe workaround, until
swagger-api/swagger-core#3421 is resolved.