Open access to schema transformations

[nebehr]

In some cases it may be useful to be able to register custom schema transformations or otherwise transform schema object prior to validation. Possible use cases:

• correct spelling of some properties in Swagger schema (e.g. "x-oneof" to "x-oneOf")
• add "type" property to schema definitions that don't have it but otherwise do describe proper objects ("type" is not a required property according to JSON Schema specification but without it most glaring discrepancies, such as giving string value to an object property, go undetected by validator)

Granted, these use cases would be most properly addressed by correcting the Swagger schema itself but in some cases it is beyond our control.

One option to achieve this would be by opening public access to SwaggerValidator(JsonNode) constructor or otherwise allow to pass already processed JsonNode to the builder.

[bjansen]

Would a new builder method like someone suggested in #15 be enough?

try (InputStream in = getClass().getResourceAsStream("/htdoc/annotations.yaml")) {
    JsonNode swaggerSpec = Yaml.mapper().readTree(in);
    validator = SwaggerValidator.forJsonSchema(swaggerSpec);
}

[nebehr]

Yes, this would allow to cover the use cases I mentioned although it would be nice not to have to re-implement transformations logic since it is already there (use case # 1 above).

Wouldn't it also make sense to expose schema factory to be able to register custom keywords if necessary?

[bjansen]

Sure, I can do that too.

[bjansen]

Here's how it will look:

JsonNode schema = Json.mapper().readTree(getClass().getResourceAsStream("schema.json"));
Map<String, String> transformations = Map.of("x-oneof", "x-oneOf");

SwaggerValidator validator = SwaggerValidator.forJsonNode(schema, transformations);

Custom transformations will be applied before built-in ones, so in this case it will go x-oneof -> x-oneOf -> oneOf.