refactor: simplify method invocation builder API

Merges method() and argumentTypes() builder methods into a single method() call
for better usability and compile-time safety. Updates all tests and documentation
to use the new API.

Author: tzolov

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/client/AnthropicChatClientMethodFunctionCallbackIT.java

@@ -59,9 +59,8 @@ void methodGetWeatherStatic() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherStatic")
+					.method("getWeatherStatic", String.class, Unit.class)
 					.targetClass(TestFunctionClass.class)
-					.argumentTypes(String.class, Unit.class)
 					.build())
 				.call()
 				.content();
@@ -82,9 +81,8 @@ void methodTurnLightNoResponse() {
 				.user("Turn light on in the living room.")
 				.functions(FunctionCallback.builder()
 					.description("Turn light on in the living room.")
-					.method("turnLight")
+					.method("turnLight", String.class, boolean.class)
 					.targetObject(targetObject)
-					.argumentTypes(String.class, boolean.class)
 					.build())
 				.call()
 				.content();
@@ -106,8 +104,7 @@ void methodGetWeatherNonStatic() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherNonStatic")
-					.argumentTypes(String.class, Unit.class)
+					.method("getWeatherNonStatic",String.class, Unit.class)
 					.targetObject(targetObject)
 					.build())
 				.call()
@@ -129,8 +126,7 @@ void methodGetWeatherToolContext() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherWithContext")
-					.argumentTypes(String.class, Unit.class, ToolContext.class)
+					.method("getWeatherWithContext", String.class, Unit.class, ToolContext.class)
 					.targetObject(targetObject)
 					.build())				
 				.toolContext(Map.of("tool", "value"))
@@ -154,8 +150,7 @@ void methodGetWeatherToolContextButNonContextMethod() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherNonStatic")
-					.argumentTypes(String.class, Unit.class)
+					.method("getWeatherNonStatic", String.class, Unit.class)
 					.targetObject(targetObject)
 					.build())
 				.toolContext(Map.of("tool", "value"))

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

@@ -61,8 +61,7 @@ void methodGetWeatherStatic() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherStatic")
-					.argumentTypes(String.class, Unit.class)
+					.method("getWeatherStatic",String.class, Unit.class)
 					.targetClass(TestFunctionClass.class)
 					.build())
 				.call()
@@ -84,8 +83,7 @@ void methodTurnLightNoResponse() {
 				.user("Turn light on in the living room.")
 				.functions(FunctionCallback.builder()
 					.description("Can turn lights on or off by room name")
-					.method("turnLight")
-					.argumentTypes(String.class, boolean.class)
+					.method("turnLight", String.class, boolean.class)
 					.targetObject(targetObject)
 					.build())
 				.call()
@@ -108,8 +106,7 @@ void methodGetWeatherNonStatic() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherNonStatic")
-					.argumentTypes(String.class, Unit.class)
+					.method("getWeatherNonStatic",String.class, Unit.class)					
 					.targetObject(targetObject)
 					.build())
 				.call()
@@ -131,8 +128,7 @@ void methodGetWeatherToolContext() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherWithContext")
-					.argumentTypes(String.class, Unit.class,  ToolContext.class)
+					.method("getWeatherWithContext", String.class, Unit.class,  ToolContext.class)					
 					.targetObject(targetObject)
 					.build())
 				.toolContext(Map.of("tool", "value"))
@@ -156,8 +152,7 @@ void methodGetWeatherToolContextButNonContextMethod() {
 				.user("What's the weather like in San Francisco, Tokyo, and Paris?  Use Celsius.")
 				.functions(FunctionCallback.builder()
 					.description("Get the weather in location")
-					.method("getWeatherNonStatic")
-					.argumentTypes(String.class, Unit.class)
+					.method("getWeatherNonStatic", String.class, Unit.class)
 					.targetObject(targetObject)
 					.build())
 				.toolContext(Map.of("tool", "value"))

spring-ai-core/src/main/java/org/springframework/ai/model/function/DefaultFunctionCallbackBuilder.java

@@ -118,9 +118,8 @@ public <I, O> FunctionInvokerBuilder<I, O> function(BiFunction<I, ToolContext, O
 	}
 
 	@Override
-	public MethodInvokerBuilder method(String methodName) {
-		Assert.hasText(methodName, "Method name must not be empty");
-		return new MethodInvokerBuilderImpl(methodName);
+	public MethodInvokerBuilder method(String methodName, Class<?>... argumentTypes) {
+		return new MethodInvokerBuilderImpl(methodName, argumentTypes);
 	}
 
 	public class FunctionInvokerBuilderImpl<I, O> implements FunctionInvokerBuilder<I, O> {
@@ -196,10 +195,13 @@ public class MethodInvokerBuilderImpl implements FunctionCallback.MethodInvokerB
 
 		private Object targetObject;
 
-		private Class<?>[] arguments = new Class[0];
+		private final Class<?>[] argumentTypes;
 
-		private MethodInvokerBuilderImpl(String methodName) {
+		private MethodInvokerBuilderImpl(String methodName, Class<?>... argumentTypes) {
+			Assert.hasText(methodName, "Method name must not be null");
+			Assert.notNull(argumentTypes, "Argument types must not be null");
 			this.methodName = methodName;
+			this.argumentTypes = argumentTypes;
 		}
 
 		public MethodInvokerBuilder targetClass(Class<?> targetClass) {
@@ -216,18 +218,11 @@ public MethodInvokerBuilder targetObject(Object methodObject) {
 			return this;
 		}
 
-		@Override
-		public MethodInvokerBuilder argumentTypes(Class<?>... arguments) {
-			Assert.notNull(arguments, "Arguments must not be null");
-			this.arguments = arguments;
-			return this;
-		}
-
 		@Override
 		public FunctionCallback build() {
 			Assert.isTrue(this.targetClass != null || this.targetObject != null,
 					"Target class or object must not be null");
-			var method = ReflectionUtils.findMethod(targetClass, methodName, arguments);
+			var method = ReflectionUtils.findMethod(targetClass, methodName, argumentTypes);
 			return new MethodFunctionCallback(this.targetObject, method, description, objectMapper);
 		}
 

spring-ai-core/src/main/java/org/springframework/ai/model/function/FunctionCallback.java

@@ -132,7 +132,7 @@ interface Builder {
 
 		<I, O> FunctionInvokerBuilder<I, O> function(BiFunction<I, ToolContext, O> biFunction);
 
-		MethodInvokerBuilder method(String methodName);
+		MethodInvokerBuilder method(String methodName, Class<?>... argumentTypes);
 
 	}
 
@@ -169,8 +169,6 @@ interface MethodInvokerBuilder {
 
 		MethodInvokerBuilder targetClass(Class<?> targetClass);
 
-		MethodInvokerBuilder argumentTypes(Class<?>... arguments);
-
 		/**
 		 * Builds the {@link FunctionCallback} instance.
 		 */

spring-ai-core/src/test/java/org/springframework/ai/model/function/MethodFunctionCallbackTests.java

@@ -58,9 +58,8 @@ public void staticMethod() throws NoSuchMethodException, SecurityException {
 		var functionCallback = FunctionCallback.builder()
 			.description("weather at location")
 			.objectMapper(new ObjectMapper())
-			.method("myStaticMethod")
+			.method("myStaticMethod", String.class, Unit.class, int.class, MyRecord.class, List.class)
 			.targetClass(TestClassWithFunctionMethods.class)
-			.argumentTypes(String.class, Unit.class, int.class, MyRecord.class, List.class)
 			.build();
 
 		String response = functionCallback.call(this.value);
@@ -82,9 +81,8 @@ public void nonStaticMethod() throws NoSuchMethodException, SecurityException {
 
 		var functionCallback = FunctionCallback.builder()
 			.description("weather at location")
-			.method("myNonStaticMethod")
+			.method("myNonStaticMethod", String.class, Unit.class, int.class, MyRecord.class, List.class)
 			.targetObject(object)
-			.argumentTypes(String.class, Unit.class, int.class, MyRecord.class, List.class)
 			.build();
 
 		String response = functionCallback.call(this.value);

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/functions.adoc

@@ -314,8 +314,7 @@ You need the `FunctionCallback.Builder` to create `MethodFunctionCallback` like
 FunctionCallback callback = FunctionCallback.builder()
     .description("Method description") // Required: Helps AI understand the function
     .objectMapper(objectMapper)             // Optional: Custom ObjectMapper
-    .method("MethodName")             // Required: The method to invoke
-    .argumentTypes(Class<?>...argumentTypes) // Required unless method has no arguments
+    .method("MethodName", Class<?>...argumentTypes) // Required: The method to invoke and its argument types
     .targetObject(targetObject)       // Required only for instance methods
     .build();
 ----
@@ -337,9 +336,8 @@ public class WeatherService {
 // Usage
 FunctionCallback callback = FunctionCallback.builder()
     .description("Get weather information for a city")
-    .method("getWeather")
+    .method("getWeather", String.class, TemperatureUnit.class)
     .targetClass(WeatherService.class)
-    .argumentTypes(String.class, TemperatureUnit.class)
     .build();
 ----
 Instance Method with ToolContext::
@@ -360,8 +358,7 @@ String response = ChatClient.create(chatModel).prompt()
     .user("Turn on the living room lights")
     .functions(FunctionCallback.builder()
         .description("Control device state")
-        .method("setDeviceState")
-        .argumentTypes(String.class,boolean.class,ToolContext.class)
+        .method("setDeviceState", String.class,boolean.class,ToolContext.class)
         .targetObject(controller)
         .build())
     .toolContext(Map.of("location", "home"))