Add getting-started module: ChatClient fluent API, system/user prompts, streaming, and provider switching via spring.ai.model.chat

getting-started/src/main/java/com/ankurm/gettingstarted/GettingStartedApplication.java

@@ -0,0 +1,12 @@
+package com.ankurm.gettingstarted;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class GettingStartedApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(GettingStartedApplication.class, args);
+    }
+}

getting-started/src/main/java/com/ankurm/gettingstarted/config/ChatClientConfig.java

@@ -0,0 +1,24 @@
+package com.ankurm.gettingstarted.config;
+
+import org.springframework.ai.chat.client.ChatClient;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * The one bean this module exists to explain. {@link ChatClient.Builder} arrives
+ * autoconfigured and already pointed at whichever {@code ChatModel} bean
+ * {@code spring.ai.model.chat} selected — this class never mentions OpenAI or Ollama
+ * by name, and that is the whole point of the properties-based switch.
+ */
+@Configuration
+public class ChatClientConfig {
+
+    @Bean
+    ChatClient chatClient(ChatClient.Builder builder) {
+        return builder
+                .defaultSystem("""
+                        You are a terse Java and Spring assistant. Answer in at most two \
+                        sentences unless the user asks for code.""")
+                .build();
+    }
+}

getting-started/src/main/java/com/ankurm/gettingstarted/web/ChatController.java

@@ -0,0 +1,51 @@
+package com.ankurm.gettingstarted.web;
+
+import org.springframework.ai.chat.client.ChatClient;
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import reactor.core.publisher.Flux;
+
+/**
+ * Three endpoints, three corners of the {@link ChatClient} fluent API:
+ * a plain call, a call with a templated system prompt, and a streamed call.
+ * See {@code docs} on ankurm.com for the walkthrough — the endpoints
+ * themselves carry no comment beyond what the method name says, deliberately,
+ * since the interesting part is the one-line body.
+ */
+@RestController
+public class ChatController {
+
+    private final ChatClient chatClient;
+
+    public ChatController(ChatClient chatClient) {
+        this.chatClient = chatClient;
+    }
+
+    @GetMapping("/api/chat")
+    public String chat(@RequestParam String message) {
+        return this.chatClient.prompt()
+                .user(message)
+                .call()
+                .content();
+    }
+
+    @GetMapping("/api/chat/as")
+    public String chatAs(@RequestParam String voice, @RequestParam String message) {
+        return this.chatClient.prompt()
+                .system(s -> s.text("Answer in the voice of a {voice}, still in two sentences.")
+                        .param("voice", voice))
+                .user(message)
+                .call()
+                .content();
+    }
+
+    @GetMapping(value = "/api/chat/stream", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
+    public Flux<String> chatStream(@RequestParam String message) {
+        return this.chatClient.prompt()
+                .user(message)
+                .stream()
+                .content();
+    }
+}

getting-started/src/main/resources/application.yml

@@ -0,0 +1,18 @@
+spring:
+  application:
+    name: getting-started
+  ai:
+    # Which provider's ChatModel bean gets built. Flip this one line, keep the code
+    # in ChatClientConfig and ChatController unchanged, and add the matching provider
+    # properties below.
+    model:
+      chat: ${CHAT_PROVIDER:openai}
+    openai:
+      api-key: ${OPENAI_API_KEY:}
+      chat:
+        model: gpt-4o
+        temperature: 0.1
+    ollama:
+      base-url: ${OLLAMA_BASE_URL:http://localhost:11434}
+      chat:
+        model: llama3.2