Support for BeanOutputConverter with non-standard enum mapping

[kamil-sita]

Expected Behavior

I'd like to see @JsonProperty style of enums with BeanOutputConverter - it'd be great to have an ability to give AI assistant a range of constant values, which aren't just Java String names. That is, I'd love to see something like:

	@PostConstruct
	public void doSomething() {
		var myWrapper = ChatClient.create(chatModel)
				.prompt("Select randomly either \"value.a\" or \"value.b\"")
				.call()
				.entity(MyWrapper.class);
		System.out.println(myWrapper.values);
	}


	public record MyWrapper(EnumValues values) {

	}

	public enum EnumValues {
		@JsonProperty("value.a")
		A,
		@JsonProperty("value.b")
		B
	}

being a correct way to use structured outputs

Current Behavior

As far as I can see, BeanOutputConverter is not really that much customizable. All the parametrization is done inside of a private method (generateSchema). In theory, one could even use @JsonProperty - it is recognized by the underling Jackson, but not by the schema generator, leading to interesting problems.

Generated schema for the code above:

{
  "$schema" : "https://json-schema.org/draft/2020-12/schema",
  "type" : "object",
  "properties" : {
    "values" : {
      "type" : "string",
      "enum" : [ "A", "B" ]
    }
  },
  "additionalProperties" : false
}

Stack trace:

Caused by: com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `xyz.SpringAiTest$EnumValues` from String "A": not one of the values accepted for Enum class: [value.a, value.b]
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 2, column: 13] (through reference chain: xyz.SpringAiTest$MyWrapper["values"])
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67) ~[jackson-databind-2.18.2.jar:2.18.2]

Context

I wanted to integrate with a service that uses non-standard constants directly, and to select values using AI assistant.

There are other ways this can be done, but as far as I understand, they either include:

1. Copying BeanOutputConverter and modifying its code
2. Implementing your own StructuredOutputConverter. For a similar case, I've tried to modify the generated schema myself to account for @JsonProperties and it works, but it's very manual and brittle
3. Mapping this enum to a String via some different code. Not the worst thing in the world, but it means that I need to refer in the conversations with the AI to the values using Java enum values, as well, as also having some code to map them.