Improve extensibility of DefaultChatOptionsBuilder

 - Enable DefaultChatOptionsBuilder to accommodate any other sub types
   - Introduce generics to support sub types that extend DefaultChatOptionsBuilder
   - Update builder methods to return the sub type

 - Make FunctionCallingOptions' builder()'s return type to accommodate sub types which can extend FunctionCallingOptions.Builder

Author: ilayaperumalg

spring-ai-core/src/main/java/org/springframework/ai/chat/prompt/ChatOptions.java

@@ -94,7 +94,7 @@ public interface ChatOptions extends ModelOptions {
 	 * {@link ChatOptions}.
 	 * @return Returns a new {@link ChatOptions.Builder}.
 	 */
-	static ChatOptions.Builder builder() {
+	static ChatOptions.Builder<? extends DefaultChatOptionsBuilder> builder() {
 		return new DefaultChatOptionsBuilder();
 	}
 

spring-ai-core/src/main/java/org/springframework/ai/chat/prompt/DefaultChatOptionsBuilder.java

@@ -21,48 +21,52 @@
 /**
  * Implementation of {@link ChatOptions.Builder} to create {@link DefaultChatOptions}.
  */
-public class DefaultChatOptionsBuilder implements ChatOptions.Builder<DefaultChatOptionsBuilder> {
+public class DefaultChatOptionsBuilder<T extends DefaultChatOptionsBuilder<T>> implements ChatOptions.Builder<T> {
 
 	private final DefaultChatOptions options = new DefaultChatOptions();
 
-	public DefaultChatOptionsBuilder model(String model) {
+	protected T self() {
+		return (T) this;
+	}
+
+	public T model(String model) {
 		this.options.setModel(model);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder frequencyPenalty(Double frequencyPenalty) {
+	public T frequencyPenalty(Double frequencyPenalty) {
 		this.options.setFrequencyPenalty(frequencyPenalty);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder maxTokens(Integer maxTokens) {
+	public T maxTokens(Integer maxTokens) {
 		this.options.setMaxTokens(maxTokens);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder presencePenalty(Double presencePenalty) {
+	public T presencePenalty(Double presencePenalty) {
 		this.options.setPresencePenalty(presencePenalty);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder stopSequences(List<String> stop) {
+	public T stopSequences(List<String> stop) {
 		this.options.setStopSequences(stop);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder temperature(Double temperature) {
+	public T temperature(Double temperature) {
 		this.options.setTemperature(temperature);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder topK(Integer topK) {
+	public T topK(Integer topK) {
 		this.options.setTopK(topK);
-		return this;
+		return self();
 	}
 
-	public DefaultChatOptionsBuilder topP(Double topP) {
+	public T topP(Double topP) {
 		this.options.setTopP(topP);
-		return this;
+		return self();
 	}
 
 	public ChatOptions build() {

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

@@ -47,10 +47,6 @@ public class DefaultFunctionCallingOptions extends DefaultChatOptions implements
 
 	private Map<String, Object> context = new HashMap<>();
 
-	public static FunctionCallingOptions.Builder builder() {
-		return new DefaultFunctionCallingOptionsBuilder();
-	}
-
 	@Override
 	public List<FunctionCallback> getFunctionCallbacks() {
 		return Collections.unmodifiableList(this.functionCallbacks);

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

@@ -22,6 +22,7 @@
 import java.util.Map;
 import java.util.Set;
 
+import org.springframework.ai.chat.prompt.DefaultChatOptionsBuilder;
 import org.springframework.util.Assert;
 
 /**
@@ -31,88 +32,50 @@
  * @author Thomas Vitale
  * @author Ilayaperumal Gopinathan
  */
-public class DefaultFunctionCallingOptionsBuilder implements FunctionCallingOptions.Builder {
+public class DefaultFunctionCallingOptionsBuilder
+		extends DefaultChatOptionsBuilder<DefaultFunctionCallingOptionsBuilder>
+		implements FunctionCallingOptions.Builder<DefaultFunctionCallingOptionsBuilder> {
 
 	private final DefaultFunctionCallingOptions functionCallingOptions = new DefaultFunctionCallingOptions();
 
-	public FunctionCallingOptions.Builder model(String model) {
-		this.functionCallingOptions.setModel(model);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder frequencyPenalty(Double frequencyPenalty) {
-		this.functionCallingOptions.setFrequencyPenalty(frequencyPenalty);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder maxTokens(Integer maxTokens) {
-		this.functionCallingOptions.setMaxTokens(maxTokens);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder presencePenalty(Double presencePenalty) {
-		this.functionCallingOptions.setPresencePenalty(presencePenalty);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder stopSequences(List<String> stopSequences) {
-		this.functionCallingOptions.setStopSequences(stopSequences);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder temperature(Double temperature) {
-		this.functionCallingOptions.setTemperature(temperature);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder topK(Integer topK) {
-		this.functionCallingOptions.setTopK(topK);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder topP(Double topP) {
-		this.functionCallingOptions.setTopP(topP);
-		return this;
-	}
-
-	public FunctionCallingOptions.Builder functionCallbacks(List<FunctionCallback> functionCallbacks) {
+	public DefaultFunctionCallingOptionsBuilder functionCallbacks(List<FunctionCallback> functionCallbacks) {
 		this.functionCallingOptions.setFunctionCallbacks(functionCallbacks);
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder functionCallbacks(FunctionCallback... functionCallbacks) {
+	public DefaultFunctionCallingOptionsBuilder functionCallbacks(FunctionCallback... functionCallbacks) {
 		Assert.notNull(functionCallbacks, "FunctionCallbacks must not be null");
 		this.functionCallingOptions.setFunctionCallbacks(List.of(functionCallbacks));
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder functions(Set<String> functions) {
+	public DefaultFunctionCallingOptionsBuilder functions(Set<String> functions) {
 		this.functionCallingOptions.setFunctions(functions);
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder function(String function) {
+	public DefaultFunctionCallingOptionsBuilder function(String function) {
 		Assert.notNull(function, "Function must not be null");
 		var set = new HashSet<>(this.functionCallingOptions.getFunctions());
 		set.add(function);
 		this.functionCallingOptions.setFunctions(set);
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder proxyToolCalls(Boolean proxyToolCalls) {
+	public DefaultFunctionCallingOptionsBuilder proxyToolCalls(Boolean proxyToolCalls) {
 		this.functionCallingOptions.setProxyToolCalls(proxyToolCalls);
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder toolContext(Map<String, Object> context) {
+	public DefaultFunctionCallingOptionsBuilder toolContext(Map<String, Object> context) {
 		Assert.notNull(context, "Tool context must not be null");
 		Map<String, Object> newContext = new HashMap<>(this.functionCallingOptions.getToolContext());
 		newContext.putAll(context);
 		this.functionCallingOptions.setToolContext(newContext);
 		return this;
 	}
 
-	public FunctionCallingOptions.Builder toolContext(String key, Object value) {
+	public DefaultFunctionCallingOptionsBuilder toolContext(String key, Object value) {
 		Assert.notNull(key, "Key must not be null");
 		Assert.notNull(value, "Value must not be null");
 		Map<String, Object> newContext = new HashMap<>(this.functionCallingOptions.getToolContext());

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

@@ -35,7 +35,7 @@ public interface FunctionCallingOptions extends ChatOptions {
 	 * @return Returns {@link DefaultFunctionCallingOptionsBuilder} to create a new
 	 * instance of {@link FunctionCallingOptions}.
 	 */
-	static FunctionCallingOptions.Builder builder() {
+	static FunctionCallingOptions.Builder<? extends FunctionCallingOptions.Builder> builder() {
 		return new DefaultFunctionCallingOptionsBuilder();
 	}
 
@@ -87,57 +87,57 @@ default void setProxyToolCalls(Boolean proxyToolCalls) {
 	/**
 	 * Builder for creating {@link FunctionCallingOptions} instance.
 	 */
-	interface Builder extends ChatOptions.Builder<Builder> {
+	interface Builder<T extends Builder<T>> extends ChatOptions.Builder<T> {
 
 		/**
 		 * The list of Function Callbacks to be registered with the Chat model.
 		 * @param functionCallbacks the list of Function Callbacks.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder functionCallbacks(List<FunctionCallback> functionCallbacks);
+		T functionCallbacks(List<FunctionCallback> functionCallbacks);
 
 		/**
 		 * The Function Callbacks to be registered with the Chat model.
 		 * @param functionCallbacks the function callbacks.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder functionCallbacks(FunctionCallback... functionCallbacks);
+		T functionCallbacks(FunctionCallback... functionCallbacks);
 
 		/**
 		 * {@link Set} of function names to be registered with the Chat model.
 		 * @param functions the {@link Set} of function names
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder functions(Set<String> functions);
+		T functions(Set<String> functions);
 
 		/**
 		 * The function name to be registered with the chat model.
 		 * @param function the name of the function.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder function(String function);
+		T function(String function);
 
 		/**
 		 * Boolean flag to indicate if the proxy ToolCalls is enabled.
 		 * @param proxyToolCalls boolean value to enable proxy ToolCalls.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder proxyToolCalls(Boolean proxyToolCalls);
+		T proxyToolCalls(Boolean proxyToolCalls);
 
 		/**
 		 * Add a {@link Map} of context values into tool context.
 		 * @param context the map representing the tool context.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder toolContext(Map<String, Object> context);
+		T toolContext(Map<String, Object> context);
 
 		/**
 		 * Add a specific key/value pair to the tool context.
 		 * @param key the key to use.
 		 * @param value the corresponding value.
 		 * @return the FunctionCallOptions Builder.
 		 */
-		Builder toolContext(String key, Object value);
+		T toolContext(String key, Object value);
 
 		/**
 		 * Builds the {@link FunctionCallingOptions}.