VectorSearchFilter.filter serializes as null causing HTTP 400 from AI Core API

Describe the Problem/Bug

When using VectorApi.search(), the VectorSearchFilter class has a filter field annotated with @JsonProperty("filter") but without @JsonInclude(JsonInclude.Include.NON_NULL). When filter is not set (the
common case), it serializes as "filter": null in the JSON request body.

The AI Core API rejects this with HTTP 400:
{"error": {"code": "400", "message": "None is not valid under any of the given schemas - 'filters.0.filter'"}}

Steps to Reproduce

  var filter = VectorSearchFilter.create()
      .id(UUID.randomUUID().toString())
      .collectionIds(List.of("*"))
      ._configuration(VectorSearchConfiguration.create().maxDocumentCount(5));

  var request = TextSearchRequest.create()
      .query("some query")
      .filters(filter);

  vectorApi.search(resourceGroupId, request); // → HTTP 400

Actual request body sent:

  {
    "query": "some query",
    "filters": [{
      "id": "...",
      "collectionIds": ["*"],
      "configuration": {"maxDocumentCount": 5},
      "collectionMetadata": [],
      "documentMetadata": [],
      "chunkMetadata": [],
      "filter": null
    }]
  }

Expected Behavior

filter should be omitted from the serialized JSON when not set, either via @JsonInclude(JsonInclude.Include.NON_NULL) on the field, or by configuring the SDK's default ObjectMapper with
NON_NULL inclusion.

Workaround: Construct the VectorApi with a custom ApiClient using an ObjectMapper configured with JsonInclude.Include.NON_NULL.

Screenshots

No response

Used Versions

SDK version: 1.19.0
Spring AI version: 1.1.5

Code Examples

// Your code here

Stack Trace

No response

Log File

Log file

...

Affected Development Phase

Getting Started

Impact

No Impact

Timeline

No response

Start with VectorSearchFilter and inspect how its filter field is serialized, then compare the default ApiClient ObjectMapper with the custom NON_NULL workaround described in the issue. Reproduce the VectorApi.search() request and confirm that an unset filter is omitted and the AI Core API no longer returns HTTP 400.