GH-912: Add customizable logger advisor (#913)

* Add customizable logger advisor
* Address review comments
* Use the OutputCaptureExtension to verify the output text

 Resolves #912

spring-ai-core/src/test/java/org/springframework/ai/chat/client/SimpleLoggerAdvisorTests.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2024-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.ai.chat.client;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.ai.chat.client.advisor.SimpleLoggerAdvisor;
+import org.springframework.ai.chat.messages.Message;
+import org.springframework.ai.chat.model.ChatModel;
+import org.springframework.ai.chat.model.ChatResponse;
+import org.springframework.ai.chat.model.Generation;
+import org.springframework.ai.chat.prompt.Prompt;
+import org.springframework.boot.test.system.CapturedOutput;
+import org.springframework.boot.test.system.OutputCaptureExtension;
+import org.springframework.test.context.ActiveProfiles;
+
+import reactor.core.publisher.Flux;
+
+/**
+ * @author Christian Tzolov
+ */
+@ExtendWith({ MockitoExtension.class, OutputCaptureExtension.class })
+@ActiveProfiles("logging-test")
+public class SimpleLoggerAdvisorTests {
+
+	@Mock
+	ChatModel chatModel;
+
+	@Captor
+	ArgumentCaptor<Prompt> promptCaptor;
+
+	@Test
+	public void callLogging(CapturedOutput output) {
+
+		when(chatModel.call(promptCaptor.capture()))
+				.thenReturn(new ChatResponse(List.of(new Generation("Your answer is ZXY"))));
+
+		var loggerAdvisor = new SimpleLoggerAdvisor();
+
+		var chatClient = ChatClient.builder(chatModel).defaultAdvisors(loggerAdvisor).build();
+
+		var content = chatClient.prompt().user("Please answer my question XYZ").call().content();
+
+		validate(content, output);
+	}
+
+	@Test
+	public void streamLogging(CapturedOutput output) {
+
+		when(chatModel.stream(promptCaptor.capture())).thenReturn(
+				Flux.generate(() -> new ChatResponse(List.of(new Generation("Your answer is ZXY"))), (state, sink) -> {
+					sink.next(state);
+					sink.complete();
+					return state;
+				}));
+
+		var loggerAdvisor = new SimpleLoggerAdvisor();
+
+		var chatClient = ChatClient.builder(chatModel).defaultAdvisors(loggerAdvisor).build();
+
+		String content = join(chatClient.prompt().user("Please answer my question XYZ").stream().content());
+
+		validate(content, output);
+	}
+
+	private void validate(String content, CapturedOutput output) {
+		assertThat(content).isEqualTo("Your answer is ZXY");
+
+		Message userMessage = promptCaptor.getValue().getInstructions().get(0);
+		assertThat(userMessage.getContent()).isEqualToIgnoringWhitespace("Please answer my question XYZ");
+
+		assertThat(output.getOut()).contains("request: AdvisedRequest", "userText=Please answer my question XYZ");
+		assertThat(output.getOut()).contains("response:", "finishReason");
+	}
+
+	private String join(Flux<String> fluxContent) {
+		return fluxContent.collectList().block().stream().collect(Collectors.joining());
+	}
+
+}

spring-ai-core/src/test/resources/application-logging-test.properties

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+logging.level.org.springframework.ai.chat.client.advisor.SimpleLoggerAdvisor=DEBUG
+logging.level.ch.qos.logback=ERROR

spring-ai-core/src/test/resources/logback.xml

@@ -0,0 +1,16 @@
+<configuration>
+
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} -%kvp- %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="debug">
+        <appender-ref ref="STDOUT" />
+    </root>
+    <logger name="org.springframework.ai.chat.client.advisor" level="DEBUG" additivity="true">
+        <appender-ref ref="STDOUT" />
+    </logger>
+
+</configuration>