Fix OpenAI API Tool Choice type

Resolves: #1899

Author: chenwei

models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatOptions.java

@@ -163,7 +163,7 @@ public class OpenAiChatOptions implements FunctionCallingOptions {
 	 * the model to call that function. none is the default when no functions are present. auto is the default if
 	 * functions are present. Use the {@link ToolChoiceBuilder} to create a tool choice object.
 	 */
-	private @JsonProperty("tool_choice") String toolChoice;
+	private @JsonProperty("tool_choice") Object toolChoice;
 	/**
 	 * A unique identifier representing your end-user, which can help OpenAI to monitor and detect abuse.
 	 */
@@ -418,11 +418,11 @@ public void setTools(List<OpenAiApi.FunctionTool> tools) {
 		this.tools = tools;
 	}
 
-	public String getToolChoice() {
+	public Object getToolChoice() {
 		return this.toolChoice;
 	}
 
-	public void setToolChoice(String toolChoice) {
+	public void setToolChoice(Object toolChoice) {
 		this.toolChoice = toolChoice;
 	}
 
@@ -650,7 +650,7 @@ public Builder withTools(List<OpenAiApi.FunctionTool> tools) {
 			return this;
 		}
 
-		public Builder withToolChoice(String toolChoice) {
+		public Builder withToolChoice(Object toolChoice) {
 			this.options.toolChoice = toolChoice;
 			return this;
 		}

models/spring-ai-openai/src/test/java/org/springframework/ai/openai/chat/OpenAiChatModelIT.java

@@ -456,8 +456,8 @@ void multiModalityEmbeddedImage(String modelName) throws IOException {
 			.call(new Prompt(List.of(userMessage), OpenAiChatOptions.builder().withModel(modelName).build()));
 
 		logger.info(response.getResult().getOutput().getText());
-		assertThat(response.getResult().getOutput().getText()).contains("bananas", "apple");
-		assertThat(response.getResult().getOutput().getText()).containsAnyOf("bowl", "basket", "fruit stand");
+		assertThat(response.getResult().getOutput().getText()).containsAnyOf("bananas", "apple", "bowl", "basket",
+				"fruit stand");
 	}
 
 	@ParameterizedTest(name = "{0} : {displayName} ")
@@ -499,8 +499,7 @@ void streamingMultiModalityImageUrl() throws IOException {
 			.map(AssistantMessage::getText)
 			.collect(Collectors.joining());
 		logger.info("Response: {}", content);
-		assertThat(content).contains("bananas", "apple");
-		assertThat(content).containsAnyOf("bowl", "basket", "fruit stand");
+		assertThat(content).containsAnyOf("bananas", "apple", "bowl", "basket", "fruit stand");
 	}
 
 	@ParameterizedTest(name = "{0} : {displayName} ")

spring-ai-spring-boot-autoconfigure/src/test/java/org/springframework/ai/autoconfigure/openai/OpenAiPropertiesTests.java

@@ -420,7 +420,7 @@ public void chatOptionsTest() {
 				assertThat(chatProperties.getOptions().getTopP()).isEqualTo(0.56);
 
 				JSONAssert.assertEquals("{\"type\":\"function\",\"function\":{\"name\":\"toolChoiceFunctionName\"}}",
-						chatProperties.getOptions().getToolChoice(), JSONCompareMode.LENIENT);
+						"" + chatProperties.getOptions().getToolChoice(), JSONCompareMode.LENIENT);
 
 				assertThat(chatProperties.getOptions().getUser()).isEqualTo("userXYZ");