@Service
public class AiService {
 private final ChatClient gemmaChatClient;
 private final ChatClient openAiChatClient;
 public AiService(ChatClient.Builder chatClientBuilder) {
 var gemmaApi = OpenAiApi.builder()
 .baseUrl("http://localhost:11434")
 .apiKey("test") // Otherwise api key required exception is thrown
 .build();
 var gemmaChatModel = OpenAiChatModel.builder()
 .openAiApi(gemmaApi)
 .build();
 var gemmaChatOptions = ChatOptions.builder()
 .model("gemma:2b")
 .build();
 this.gemmaChatClient = ChatClient
 .builder(gemmaChatModel)
 .defaultOptions(gemmaChatOptions)
 .build();
 var openAiChatOptions = ChatOptions.builder()
 .model("gpt-4.1-nano")
 .build();
 this.openAiChatClient = chatClientBuilder
 .defaultOptions(openAiChatOptions)
 .build();
 }
 public String askGemma(String message) {
 return gemmaChatClient.prompt()
 .user(message)
 .call()
 .content();
 }
 public String askOpenai(String message) {
 return openAiChatClient.prompt()
 .user(message)
 .call()
 .content();
 }
}

 @PostMapping(value = "/askai")
 public String askai(@RequestParam("message") String message,
 @RequestParam(value = "model", defaultValue = "openai") String model) {
 return switch (model) {
 case "openai" -> aiService.askOpenai(message);
 case "gemma" -> aiService.askGemma(message);
 default -> throw new IllegalStateException("Unexpected value: " + model);
 };
 }

$ ollama ls 
NAME ID SIZE MODIFIED 
gemma:2b b50d6c999e59 1.7 GB 8 days ago 

$ http POST :8080/askai message=="Are you trained by openai?" model=="openai" -b 
Yes, I am developed and trained by OpenAI.

$ http POST :8080/askai message=="Are you trained by google?" model=="gemma" -b 
I am a large language model, trained by Google. I am a conversational AI that can engage in human-like conversations on a wide range of topics.