fix issue

Signed-off-by: wind57 <[email protected]>

Author: wind57

spring-cloud-kubernetes-commons/src/main/java/org/springframework/cloud/kubernetes/commons/config/ConfigUtils.java

@@ -339,10 +339,11 @@ public static <T> void registerSingle(ConfigurableBootstrapContext bootstrapCont
 			String name, ApplicationListener<?> listener) {
 		bootstrapContext.registerIfAbsent(cls, BootstrapRegistry.InstanceSupplier.of(instance));
 		bootstrapContext.addCloseListener(event -> {
-			if (event.getApplicationContext().getBeanFactory().getSingleton(name) == null) {
-				event.getApplicationContext()
-					.getBeanFactory()
-					.registerSingleton(name, event.getBootstrapContext().get(cls));
+
+			T singleton = event.getBootstrapContext().get(cls);
+
+			if (event.getApplicationContext().getBeanFactory().getSingleton(name) == null && singleton != null) {
+				event.getApplicationContext().getBeanFactory().registerSingleton(name, singleton);
 				event.getApplicationContext().addApplicationListener(listener);
 			}
 		});

spring-cloud-kubernetes-fabric8-discovery/pom.xml

@@ -49,6 +49,13 @@
 		</dependency>
 
 		<!-- Testing Dependencies -->
+
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-kubernetes-fabric8-config</artifactId>
+			<scope>test</scope>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>

spring-cloud-kubernetes-fabric8-discovery/src/test/java/org/springframework/cloud/kubernetes/fabric8/discovery/Fabric8ConfigServerTest.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2013-2025 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.cloud.kubernetes.fabric8.discovery;
+
+import com.github.tomakehurst.wiremock.WireMockServer;
+import com.github.tomakehurst.wiremock.client.WireMock;
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+
+import static com.github.tomakehurst.wiremock.client.WireMock.aResponse;
+import static com.github.tomakehurst.wiremock.client.WireMock.get;
+import static com.github.tomakehurst.wiremock.client.WireMock.stubFor;
+import static com.github.tomakehurst.wiremock.client.WireMock.urlEqualTo;
+import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.options;
+
+/**
+ * Test that proves that this
+ * <a href="https://github.com/spring-cloud/spring-cloud-kubernetes/issues/1831">issue</a>
+ * is fixed.
+ *
+ * @author wind57
+ */
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT, properties = {
+		"spring.main.cloud-platform=KUBERNETES", "spring.config.import=kubernetes:, optional:configserver:" })
+class Fabric8ConfigServerTest {
+
+	private static WireMockServer wireMockServer;
+
+	@Autowired
+	private ApplicationContext applicationContext;
+
+	@BeforeAll
+	static void beforeAll() {
+		wireMockServer = new WireMockServer(options().port(8888));
+		wireMockServer.start();
+		WireMock.configureFor("localhost", wireMockServer.port());
+	}
+
+	@AfterAll
+	static void after() {
+		WireMock.shutdownServer();
+		wireMockServer.stop();
+	}
+
+	@Test
+	void test() {
+		stubFor(get(urlEqualTo("/application/default")).willReturn(aResponse().withStatus(200).withBody("{}")));
+		Assertions.assertThat(applicationContext).isNotNull();
+	}
+
+	@SpringBootApplication
+	protected static class TestConfig {
+
+	}
+
+}