alibaba/spring-ai-alibaba · error · RuntimeException

rerank response is null.

Error message

rerank response is null.

What it means

DashscopeReranker.process calls the DashScope rerank endpoint through a RetryTemplate; if the HTTP response entity has a null body, it throws a plain RuntimeException "rerank response is null.". This indicates the rerank API returned no payload despite (apparently) completing, so no relevance scores can be computed.

Source

Thrown at spring-ai-alibaba-admin/spring-ai-alibaba-admin-server-core/src/main/java/com/alibaba/cloud/ai/studio/core/model/reranker/dashscope/DashscopeReranker.java:103

	 */
	@NotNull
	@Override
	public List<Document> process(@NotNull Query query, @NotNull List<Document> documents) {
		if (CollectionUtils.isEmpty(documents)) {
			return documents;
		}

		Assert.notNull(query, "query must not be null");
		Assert.notNull(documents, "documents must not be null");

		DashScopeApi.RerankRequest rerankRequest = createRequest(query, documents, options);

		ResponseEntity<DashScopeApi.RerankResponse> responseEntity = this.retryTemplate
			.execute(ctx -> this.dashscopeApi.rerankEntity(rerankRequest));

		var response = responseEntity.getBody();
		if (response == null) {
			throw new RuntimeException("rerank response is null.");
		}

		return response.output().results().stream().map(data -> {
			var doc = documents.get(data.index());
			return Document.builder()
				.score(data.relevanceScore())
				.id(doc.getId())
				.text(doc.getText())
				.metadata(doc.getMetadata())
				.media(doc.getMedia())
				.build();
		}).toList();
	}

	/**
	 * Creates a rerank request for the DashScope API.
	 * @param query The search query
	 * @param documents List of documents to rerank

View on GitHub (pinned to f82da0b50f)

Solutions

1. Log the HTTP status code of responseEntity when body is null to identify the root cause (401/429/5xx).
2. Verify the DashScope API key and rerank model name are valid; fix credentials if the endpoint is rejecting the request.
3. Retry the request or add a fallback that returns the original document order when reranking fails.
4. Upgrade/patch the client to throw a typed exception (e.g. BizException with http-error-response) instead of a bare RuntimeException.

Example fix

// before
var response = responseEntity.getBody();
if (response == null) {
    throw new RuntimeException("rerank response is null.");
}
// after
var response = responseEntity.getBody();
if (response == null) {
    throw new BizException(ErrorCode.UPSTREAM_ERROR.toError("rerank response is null, status=" + responseEntity.getStatusCode()));
}

try {
    List<Document> ranked = reranker.process(query, documents, topK);
} catch (RuntimeException e) {
    if (e.getMessage() != null && e.getMessage().contains("rerank response is null")) {
        // fall back to original document order
        return documents;
    }
    throw e;
}

When it happens

Trigger: dashscopeApi.rerankEntity(rerankRequest) returns a ResponseEntity whose getBody() is null — e.g. a 204/empty-body response, a transport-level failure not retried, or an error response that is not converted to an exception before body access.

Common situations: DashScope service degradation or throttling returning empty bodies; invalid API key producing an error body the client doesn't deserialize; network proxy stripping response bodies; model name for rerank misconfigured so the service returns nothing.

Related errors

• Oauth2CallError
• InvalidParameter
• NotSupportOperation Only Support post/get
• WORKFLOW_EXECUTE_ERROR
• MISSING_PARAMS

AI-assisted analysis of alibaba/spring-ai-alibaba@f82da0b50f (2026-09-09). Data as JSON: /api/errors/fd28fcc1b2033548. Report an issue: GitHub.