fix: Fixed AgentStaticLoader bean registration using ApplicationContextInitializer and resolved OpenTelemetry double initialization in tests

This CL fixes a bug where agents provided to AdkWebServer.start() were not used. The previous implementation set a static field that Spring's dependency injection ignored, always using CompiledAgentLoader. The fix involves programmatically registering an AgentStaticLoader instance as a bean within the Spring context using an ApplicationContextInitializer, ensuring it's correctly injected. The bean name for the loader has been standardized to "agentProvider", and tutorial documentation is updated to reflect the changes.

PiperOrigin-RevId: 800576785

Author: Doris26

dev/src/main/java/com/google/adk/web/AdkWebServer.java

@@ -81,11 +81,13 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.HttpStatus;
@@ -124,9 +126,6 @@ public class AdkWebServer implements WebMvcConfigurer {
 
   private static final Logger log = LoggerFactory.getLogger(AdkWebServer.class);
 
-  // Static agent loader for programmatic startup
-  private static AgentLoader AGENT_LOADER;
-
   // WebSocket constants
   private static final String LIVE_REQUEST_QUEUE_ATTR = "liveRequestQueue";
   private static final String LIVE_SUBSCRIPTION_ATTR = "liveSubscription";
@@ -195,7 +194,7 @@ public static class RunnerService {
 
     @Autowired
     public RunnerService(
-        @Qualifier("agentLoader") AgentLoader agentProvider,
+        AgentLoader agentProvider,
         BaseArtifactService artifactService,
         BaseSessionService sessionService,
         BaseMemoryService memoryService) {
@@ -278,11 +277,24 @@ public SdkTracerProvider sdkTracerProvider(ApiServerSpanExporter apiServerSpanEx
     @Bean
     public OpenTelemetry openTelemetrySdk(SdkTracerProvider sdkTracerProvider) {
       otelLog.debug("Configuring OpenTelemetrySdk and registering globally.");
-      OpenTelemetrySdk otelSdk =
-          OpenTelemetrySdk.builder().setTracerProvider(sdkTracerProvider).buildAndRegisterGlobal();
 
-      Runtime.getRuntime().addShutdownHook(new Thread(otelSdk::close));
-      return otelSdk;
+      // Check if OpenTelemetry has already been set globally (common in tests)
+      try {
+        io.opentelemetry.api.GlobalOpenTelemetry.get();
+        // If we get here, it's already set, so just return a new instance without global
+        // registration
+        otelLog.debug("OpenTelemetry already registered globally, creating non-global instance.");
+        return OpenTelemetrySdk.builder().setTracerProvider(sdkTracerProvider).build();
+      } catch (IllegalStateException e) {
+        // GlobalOpenTelemetry hasn't been set yet, safe to register globally
+        otelLog.debug("Registering OpenTelemetry globally.");
+        OpenTelemetrySdk otelSdk =
+            OpenTelemetrySdk.builder()
+                .setTracerProvider(sdkTracerProvider)
+                .buildAndRegisterGlobal();
+        Runtime.getRuntime().addShutdownHook(new Thread(otelSdk::close));
+        return otelSdk;
+      }
     }
   }
 
@@ -623,15 +635,15 @@ public static class AgentController {
     public AgentController(
         BaseSessionService sessionService,
         BaseArtifactService artifactService,
-        @Qualifier("agentLoader") AgentLoader agentProvider,
+        AgentLoader agentProvider,
         ApiServerSpanExporter apiServerSpanExporter,
         RunnerService runnerService) {
       this.sessionService = sessionService;
       this.artifactService = artifactService;
       this.agentProvider = agentProvider;
       this.apiServerSpanExporter = apiServerSpanExporter;
       this.runnerService = runnerService;
-      ImmutableList<String> agentNames = agentProvider.listAgents();
+      ImmutableList<String> agentNames = this.agentProvider.listAgents();
       log.info(
           "AgentController initialized with {} dynamic agents: {}", agentNames.size(), agentNames);
       if (agentNames.isEmpty()) {
@@ -1862,11 +1874,23 @@ public static void main(String[] args) {
   }
 
   // TODO(vorburger): #later return Closeable, which can stop the server (and resets static)
-  public static synchronized void start(BaseAgent... agents) {
-    if (AGENT_LOADER != null) {
-      throw new IllegalStateException("AdkWebServer can only be started once.");
-    }
-    AGENT_LOADER = new AgentStaticLoader(agents);
-    main(new String[0]);
+  public static void start(BaseAgent... agents) {
+    // Disable CompiledAgentLoader by setting property to prevent its creation
+    System.setProperty("adk.agents.loader", "static");
+
+    // Create Spring Application with custom initializer
+    SpringApplication app = new SpringApplication(AdkWebServer.class);
+    app.addInitializers(
+        new ApplicationContextInitializer<ConfigurableApplicationContext>() {
+          @Override
+          public void initialize(ConfigurableApplicationContext context) {
+            // Register the AgentStaticLoader bean before context refresh
+            DefaultListableBeanFactory beanFactory =
+                (DefaultListableBeanFactory) context.getBeanFactory();
+            beanFactory.registerSingleton("agentLoader", new AgentStaticLoader(agents));
+          }
+        });
+
+    app.run(new String[0]);
   }
 }

dev/src/main/java/com/google/adk/web/AgentStaticLoader.java

@@ -26,8 +26,6 @@
 import com.google.common.collect.ImmutableMap;
 import java.util.NoSuchElementException;
 import javax.annotation.Nonnull;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
-import org.springframework.stereotype.Service;
 
 /**
  * Static Agent Loader for programmatically provided agents.
@@ -36,23 +34,10 @@
  * through the AgentLoader interface. Perfect for cases where you already have agent instances and
  * just need a convenient way to wrap them in an AgentLoader.
  *
- * <p>Example usage:
- *
- * <pre>
- * List&lt;BaseAgent&gt; agents = Arrays.asList(new MyAgent(), new CodeAssistant());
- * AgentLoader loader = new AgentStaticLoader(agents.toArray(new BaseAgent[0]));
- * app.beanFactory().setAgentLoader(loader);
- * </pre>
- *
- * <p>Configuration:
- *
- * <ul>
- *   <li>To enable this loader: {@code adk.agents.loader=static}
- * </ul>
+ * <p>This class is not a Spring component by itself - instances are created programmatically and
+ * then registered as beans via factory methods.
  */
-@Service("staticAgentLoader")
-@ConditionalOnProperty(name = "adk.agents.loader", havingValue = "static", matchIfMissing = false)
-public class AgentStaticLoader implements AgentLoader {
+class AgentStaticLoader implements AgentLoader {
 
   private final ImmutableMap<String, BaseAgent> agents;
 

dev/src/test/java/com/google/adk/web/AgentStaticLoaderTest.java

@@ -0,0 +1,28 @@
+package com.google.adk.web;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.google.adk.agents.BaseAgent;
+import com.google.adk.agents.LlmAgent;
+import org.junit.jupiter.api.Test;
+
+public class AgentStaticLoaderTest {
+
+  @Test
+  public void testAgentStaticLoaderApproach() {
+    BaseAgent testAgent =
+        LlmAgent.builder()
+            .name("test_agent")
+            .model("gemini-2.0-flash-lite")
+            .description("Test agent for demonstrating AgentStaticLoader")
+            .instruction("You are a test agent.")
+            .build();
+
+    AgentStaticLoader staticLoader = new AgentStaticLoader(testAgent);
+
+    assertTrue(staticLoader.listAgents().contains("test_agent"));
+    assertEquals(testAgent, staticLoader.loadAgent("test_agent"));
+    assertEquals("test_agent", staticLoader.loadAgent("test_agent").name());
+  }
+}

tutorials/city-time-weather/README.md

@@ -16,28 +16,34 @@ cd /google_adk/tutorials/city-time-weather
 
 ## Running the Agent
 
-This tutorial supports multiple ways to load and run the agent:
+This tutorial demonstrates two different agent loading approaches:
 
-### Option 1: Using CompiledAgentLoader (Recommended)
+### Option 1: Using CompiledAgentLoader (Automatic Discovery)
 
-The simplest approach - automatically discovers agents with `ROOT_AGENT` fields:
+Automatically discovers agents with `ROOT_AGENT` fields in compiled classes:
 
 ```shell
 mvn exec:java -Dadk.agents.source-dir=$PWD
 ```
 
-### Option 2: Using AgentStaticLoader Programmatically
+This approach:
+- Uses Spring Boot to start `AdkWebServer` directly
+- `CompiledAgentLoader` scans `target/classes` for `ROOT_AGENT` fields
+- Automatically loads the `CityTimeWeather.ROOT_AGENT`
 
-For programmatic control, use the `AdkWebServer.start()` method:
+### Option 2: Using AgentStaticLoader (Programmatic)
 
+Explicitly provides pre-created agent instances:
+
+With custom port:
 ```shell
-mvn exec:java -Dexec.mainClass="com.google.adk.tutorials.CityTimeWeather"
+mvn exec:java -Dexec.mainClass="com.google.adk.tutorials.CityTimeWeather" -Dserver.port=8081
 ```
 
-This uses the built-in `main` method that calls:
-```java
-AdkWebServer.start(ROOT_AGENT);
-```
+This approach:
+- Calls `CityTimeWeather.main()` which executes `AdkWebServer.start(ROOT_AGENT)`
+- Directly provides the agent instance programmatically
+- Uses `AgentStaticLoader` with the provided agent
 
 ## Usage
 
@@ -46,10 +52,13 @@ Once running, you can interact with the agent through:
 - API endpoints for city time and weather queries
 - Agent name: `multi_tool_agent`
 
-## Agent Loaders Explained
+## Agent Loading Approaches
+
+This tutorial demonstrates both agent loading strategies:
+
+- **CompiledAgentLoader (Option 1)**: Automatically discovers agents in compiled classes. Good for development and when you have multiple agents.
+- **AgentStaticLoader (Option 2)**: Takes pre-created agent instances programmatically. Good for production and when you need precise control.
 
-- **CompiledAgentLoader**: Scans directories for compiled classes with `ROOT_AGENT` fields
-- **AgentStaticLoader**: Takes pre-created agent instances programmatically
-- Choose based on whether you want automatic discovery or programmatic control
+Choose Option 1 for automatic discovery, Option 2 for programmatic control.
 
 See https://google.github.io/adk-docs/get-started/quickstart/#java for more information.

tutorials/city-time-weather/pom.xml

@@ -44,5 +44,10 @@
         </exclusion>
       </exclusions>
     </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-simple</artifactId>
+      <version>1.7.36</version>
+    </dependency>
   </dependencies>
 </project>