Document methods of starting Testcontainer containers

Update the reference documentation to provide more details about the
three supported methods of starting Testcontainer containers.

See gh-44187

Signed-off-by: Vanio Begic <vanio.begic123@gmail.com>

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/testcontainers/beandeclaration/BeanDeclarationConfig.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2025 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.boot.docs.testing.testcontainers.beandeclaration;
+
+import org.testcontainers.containers.MongoDBContainer;
+import org.testcontainers.utility.DockerImageName;
+
+import org.springframework.boot.test.context.TestConfiguration;
+import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
+import org.springframework.context.annotation.Bean;
+
+@TestConfiguration(proxyBeanMethods = false)
+class BeanDeclarationConfig {
+
+	@ServiceConnection
+	@Bean
+	MongoDBContainer container() {
+		return new MongoDBContainer(DockerImageName.parse("mongo:latest"));
+	}
+
+}

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/testcontainers/beandeclaration/SpringTest.java

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+/*
+ * Copyright 2012-2025 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.boot.docs.testing.testcontainers.beandeclaration;
+
+import org.junit.jupiter.api.Test;
+import org.testcontainers.containers.MongoDBContainer;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Import;
+
+@SpringBootTest
+@Import(BeanDeclarationConfig.class)
+class SpringTest {
+
+	@Autowired
+	private MongoDBContainer mongo;
+
+	@Test
+	void doTest() {
+		System.out.println("Mongo db is running: " + this.mongo.isRunning());
+	}
+
+}

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/testcontainers/importcontainers/MyConfiguration.java

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+/*
+ * Copyright 2012-2025 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.boot.docs.testing.testcontainers.importcontainers;
+
+import org.springframework.boot.test.context.TestConfiguration;
+import org.springframework.boot.testcontainers.context.ImportTestcontainers;
+
+@TestConfiguration(proxyBeanMethods = false)
+@ImportTestcontainers(MyInterface.class)
+class MyConfiguration {
+
+}

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/testcontainers/importcontainers/MyInterface.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2025 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.boot.docs.testing.testcontainers.importcontainers;
+
+import org.testcontainers.containers.MongoDBContainer;
+import org.testcontainers.containers.Neo4jContainer;
+import org.testcontainers.junit.jupiter.Container;
+
+import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
+
+interface MyInterface {
+
+	@Container
+	@ServiceConnection
+	MongoDBContainer mongoContainer = new MongoDBContainer("mongo:5.0");
+
+	@Container
+	@ServiceConnection
+	Neo4jContainer<?> neo4jContainer = new Neo4jContainer<>("neo4j:5");
+
+}

spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/testing/testcontainers/beandeclaration/BeanDeclarationConfig.kt

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+package org.springframework.boot.docs.testing.testcontainers.beandeclaration
+
+import org.springframework.boot.test.context.TestConfiguration
+import org.springframework.boot.testcontainers.service.connection.ServiceConnection
+import org.springframework.context.annotation.Bean
+import org.testcontainers.containers.MongoDBContainer
+import org.testcontainers.utility.DockerImageName
+
+
+@TestConfiguration(proxyBeanMethods = false)
+internal class BeanDeclarationConfig {
+	@ServiceConnection
+	@Bean
+	fun container(): MongoDBContainer {
+		return MongoDBContainer(DockerImageName.parse("mongo:latest"))
+	}
+}

spring-boot-project/spring-boot-docs/src/main/kotlin/org/springframework/boot/docs/testing/testcontainers/beandeclaration/SpringTest.kt

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+package org.springframework.boot.docs.testing.testcontainers.beandeclaration
+
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.context.SpringBootTest
+import org.springframework.context.annotation.Import
+import org.testcontainers.containers.MongoDBContainer
+
+@SpringBootTest
+@Import(BeanDeclarationConfig::class)
+class SpringTest {
+	@Autowired
+	private val mongo: MongoDBContainer? = null
+
+	@Test
+	fun doTest() {
+		println("Mongo db is running: " + mongo!!.isRunning)
+	}
+}