ClientMcp*HandlersRegistry: support beans with unresolvable types (#4918)

- Fixes gh-4917

Signed-off-by: Daniel Garnier-Moiroux <[email protected]>

Author: Kehrlann

mcp/mcp-annotations-spring/src/main/java/org/springframework/ai/mcp/annotation/spring/AbstractClientMcpHandlerRegistry.java

@@ -74,7 +74,14 @@ public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
 				// Only process singleton beans, not scoped beans
 				continue;
 			}
-			var foundAnnotations = this.scan(AutoProxyUtils.determineTargetClass(beanFactory, beanName));
+			Class<?> beanClass = AutoProxyUtils.determineTargetClass(beanFactory, beanName);
+			if (beanClass == null) {
+				// If we cannot determine the bean class, we cannot scan it before
+				// it is really resolved. This is very likely an infrastructure-level
+				// bean, not a "service" type, skip it entirely.
+				continue;
+			}
+			var foundAnnotations = this.scan(beanClass);
 			if (!foundAnnotations.isEmpty()) {
 				this.allAnnotatedBeans.add(beanName);
 			}

mcp/mcp-annotations-spring/src/test/java/org/springframework/ai/mcp/annotation/spring/ClientMcpAsyncHandlersRegistryTests.java

@@ -38,6 +38,7 @@
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.InstanceOfAssertFactories.type;
 
@@ -340,6 +341,16 @@ void supportsProxiedClass() {
 		assertThat(registry.getCapabilities("client-1").elicitation()).isNotNull();
 	}
 
+	@Test
+	void skipsUnknownBeanClass() {
+		var registry = new ClientMcpAsyncHandlersRegistry();
+		var beanFactory = new DefaultListableBeanFactory();
+		beanFactory.registerBeanDefinition("myConfig",
+				BeanDefinitionBuilder.genericBeanDefinition().getBeanDefinition());
+
+		assertThatNoException().isThrownBy(() -> registry.postProcessBeanFactory(beanFactory));
+	}
+
 	static class ClientCapabilitiesConfiguration {
 
 		@McpElicitation(clients = { "client-1", "client-2" })

mcp/mcp-annotations-spring/src/test/java/org/springframework/ai/mcp/annotation/spring/ClientMcpSyncHandlersRegistryTests.java

@@ -37,6 +37,7 @@
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.InstanceOfAssertFactories.type;
 
@@ -332,6 +333,16 @@ void supportsProxiedClass() {
 		assertThat(registry.getCapabilities("client-1").elicitation()).isNotNull();
 	}
 
+	@Test
+	void skipsUnknownBeanClass() {
+		var registry = new ClientMcpAsyncHandlersRegistry();
+		var beanFactory = new DefaultListableBeanFactory();
+		beanFactory.registerBeanDefinition("myConfig",
+				BeanDefinitionBuilder.genericBeanDefinition().getBeanDefinition());
+
+		assertThatNoException().isThrownBy(() -> registry.postProcessBeanFactory(beanFactory));
+	}
+
 	static class ClientCapabilitiesConfiguration {
 
 		@McpElicitation(clients = { "client-1", "client-2" })