alibaba--nacos/specs/en/http-api/response-error-spec.md

HTTP API Response And Error Spec

This document refines the response contract from the HTTP API Spec. Authorization-related failures are defined with the HTTP Authorization Spec, and current endpoint coverage is recorded in the V3 API Surface.

1. JSON Response Envelope

The default v3 JSON response envelope is com.alibaba.nacos.api.model.v2.Result<T>:

{
  "code": 0,
  "message": "success",
  "data": {}
}

Endpoint docs must state the data type and any non-default HTTP status.

2. Response Exceptions

Current intentional response-shape exceptions:

• File download endpoints may return ResponseEntity<byte[]>.
• Streaming copilot endpoints return Server-Sent Events.
• Health readiness may return HTTP 500 with a Result<String> body when not ready.
• Some legacy or operational endpoints may return plain text. These should be kept only when confirmed as compatibility behavior.

3. Error Handling

Controllers annotated with @NacosApi use NacosApiExceptionHandler for common v3 errors:

Exception type	HTTP status	Result code source
NacosApiException	exception error code	detailed API error code
NacosException	exception error code	SERVER_ERROR
missing request parameter	400	PARAMETER_MISSING
invalid argument or number format	400	PARAMETER_VALIDATE_ERROR
media type errors	400	MEDIA_TYPE_ERROR
AccessException	403	ACCESS_DENIED
data access, servlet, or IO failures	500	DATA_ACCESS_ERROR
unhandled exceptions	500	generic failure

4. Exception Handler Convergence

Nacos-owned v3 HTTP APIs should converge on @NacosApi and NacosApiExceptionHandler for unified exception handling. Module-level exception handlers that predate the v3 API model should not define a different response shape for v3 APIs.

Plugin-style modules may keep their own exception handler when they intentionally own a separate API surface. The common extension boundary is defined by the Nacos Plugin Spec. PrometheusApiExceptionHandler is an example of this kind of plugin-style exception handler.

Known convergence items:

• config/server/exception/GlobalExceptionHandler still applies to com.alibaba.nacos.config.server and can return plain text ResponseEntity<String>.
• naming/exception/ResponseExceptionHandler still applies to com.alibaba.nacos.naming and can return plain text ResponseEntity<String>.
• ConfigOpenApiController imports NacosApi but is not currently annotated with @NacosApi.

These items should be treated as pending cleanup so Config and Naming v3 APIs use the same Result<T> error contract as other Nacos v3 APIs.