Refactor(observation): add null-safety checks and apply @OverRide annotation

- Added `Assert.notNull(context, "context cannot be null")` in
  getLowCardinalityKeyValues and getHighCardinalityKeyValues methods
  to enforce null-safety and avoid potential NPEs.
- Applied @OverRide annotation to methods in DefaultChatClientBuilder
  for consistency and better readability.

Signed-off-by: KoreaNirsa <[email protected]>

Author: KoreaNirsa

spring-ai-client-chat/src/main/java/org/springframework/ai/chat/client/DefaultChatClientBuilder.java

@@ -69,39 +69,47 @@ public DefaultChatClientBuilder(ChatModel chatModel, ObservationRegistry observa
 				customObservationConvention, Map.of(), null);
 	}
 
+	@Override
 	public ChatClient build() {
 		return new DefaultChatClient(this.defaultRequest);
 	}
 
+	@Override
 	public Builder clone() {
 		return this.defaultRequest.mutate();
 	}
 
+	@Override
 	public Builder defaultAdvisors(Advisor... advisors) {
 		this.defaultRequest.advisors(advisors);
 		return this;
 	}
 
+	@Override
 	public Builder defaultAdvisors(Consumer<ChatClient.AdvisorSpec> advisorSpecConsumer) {
 		this.defaultRequest.advisors(advisorSpecConsumer);
 		return this;
 	}
 
+	@Override
 	public Builder defaultAdvisors(List<Advisor> advisors) {
 		this.defaultRequest.advisors(advisors);
 		return this;
 	}
 
+	@Override
 	public Builder defaultOptions(ChatOptions chatOptions) {
 		this.defaultRequest.options(chatOptions);
 		return this;
 	}
 
+	@Override
 	public Builder defaultUser(String text) {
 		this.defaultRequest.user(text);
 		return this;
 	}
 
+	@Override
 	public Builder defaultUser(Resource text, Charset charset) {
 		Assert.notNull(text, "text cannot be null");
 		Assert.notNull(charset, "charset cannot be null");
@@ -114,20 +122,24 @@ public Builder defaultUser(Resource text, Charset charset) {
 		return this;
 	}
 
+	@Override
 	public Builder defaultUser(Resource text) {
 		return this.defaultUser(text, Charset.defaultCharset());
 	}
 
+	@Override
 	public Builder defaultUser(Consumer<PromptUserSpec> userSpecConsumer) {
 		this.defaultRequest.user(userSpecConsumer);
 		return this;
 	}
 
+	@Override
 	public Builder defaultSystem(String text) {
 		this.defaultRequest.system(text);
 		return this;
 	}
 
+	@Override
 	public Builder defaultSystem(Resource text, Charset charset) {
 		Assert.notNull(text, "text cannot be null");
 		Assert.notNull(charset, "charset cannot be null");
@@ -140,10 +152,12 @@ public Builder defaultSystem(Resource text, Charset charset) {
 		return this;
 	}
 
+	@Override
 	public Builder defaultSystem(Resource text) {
 		return this.defaultSystem(text, Charset.defaultCharset());
 	}
 
+	@Override
 	public Builder defaultSystem(Consumer<PromptSystemSpec> systemSpecConsumer) {
 		this.defaultRequest.system(systemSpecConsumer);
 		return this;
@@ -179,11 +193,13 @@ public Builder defaultToolCallbacks(ToolCallbackProvider... toolCallbackProvider
 		return this;
 	}
 
+	@Override
 	public Builder defaultToolContext(Map<String, Object> toolContext) {
 		this.defaultRequest.toolContext(toolContext);
 		return this;
 	}
 
+	@Override
 	public Builder defaultTemplateRenderer(TemplateRenderer templateRenderer) {
 		Assert.notNull(templateRenderer, "templateRenderer cannot be null");
 		this.defaultRequest.templateRenderer(templateRenderer);

spring-ai-client-chat/src/main/java/org/springframework/ai/chat/client/observation/DefaultChatClientObservationConvention.java

@@ -29,6 +29,7 @@
 import org.springframework.ai.observation.ObservabilityHelper;
 import org.springframework.ai.observation.conventions.SpringAiKind;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 
@@ -66,6 +67,7 @@ public String getContextualName(ChatClientObservationContext context) {
 
 	@Override
 	public KeyValues getLowCardinalityKeyValues(ChatClientObservationContext context) {
+		Assert.notNull(context, "context cannot be null");
 		return KeyValues.of(aiOperationType(context), aiProvider(context), springAiKind(), stream(context));
 	}
 
@@ -90,6 +92,7 @@ protected KeyValue stream(ChatClientObservationContext context) {
 
 	@Override
 	public KeyValues getHighCardinalityKeyValues(ChatClientObservationContext context) {
+		Assert.notNull(context, "context cannot be null");
 		var keyValues = KeyValues.empty();
 		keyValues = advisors(keyValues, context);
 		keyValues = conversationId(keyValues, context);