Fallback beans (#17357)

* Fallback beans in Spring

* Fallback beans in Spring

* Fallback beans in Spring

Author: abh1navv

spring-boot-modules/spring-boot-3/pom.xml

@@ -211,9 +211,17 @@
         <maven-surefire-plugin.version>3.0.0-M7</maven-surefire-plugin.version>
         <start-class>com.baeldung.sample.TodoApplication</start-class>
         <mockserver.version>5.14.0</mockserver.version>
-        <spring-boot.version>3.2.4</spring-boot.version>
+        <spring-boot.version>3.4.0-M1</spring-boot.version>
         <lombok-mapstruct-binding.version>0.2.0</lombok-mapstruct-binding.version>
         <springdoc-openapi-webmvc-ui.version>2.5.0</springdoc-openapi-webmvc-ui.version>
     </properties>
 
+    <repositories>
+        <repository>
+            <id>spring-milestone</id>
+            <name>Spring Milestone</name>
+            <url>https://repo.spring.io/milestone</url>
+        </repository>
+    </repositories>
+
 </project>

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/fallback/MessagingApplication.java

@@ -0,0 +1,14 @@
+package com.baeldung.fallback;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+
+@SpringBootApplication
+public class MessagingApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(MessagingApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/fallback/messaging/DevelopmentMessagingService.java

@@ -0,0 +1,14 @@
+package com.baeldung.fallback.messaging;
+
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+
+@Service
+@Profile("!test")
+public class DevelopmentMessagingService implements MessagingService {
+
+    @Override
+    public void sendMessage(String text) {
+        // implementation in development environment
+    }
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/fallback/messaging/FallbackMessagingService.java

@@ -0,0 +1,14 @@
+package com.baeldung.fallback.messaging;
+
+import org.springframework.context.annotation.Fallback;
+import org.springframework.stereotype.Service;
+
+@Service
+@Fallback
+public class FallbackMessagingService implements MessagingService {
+
+    @Override
+    public void sendMessage(String text) {
+        // fallback implementation
+    }
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/fallback/messaging/MessagingService.java

@@ -0,0 +1,5 @@
+package com.baeldung.fallback.messaging;
+
+public interface MessagingService {
+    void sendMessage(String text);
+}

spring-boot-modules/spring-boot-3/src/main/java/com/baeldung/fallback/messaging/ProductionMessagingService.java

@@ -0,0 +1,16 @@
+package com.baeldung.fallback.messaging;
+
+import org.springframework.context.annotation.Primary;
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+
+@Service
+@Profile("production")
+@Primary
+public class ProductionMessagingService implements MessagingService {
+
+    @Override
+    public void sendMessage(String text) {
+        // implementation in production environment
+    }
+}

spring-boot-modules/spring-boot-3/src/test/java/com/baeldung/fallback/DevelopmentMessagingServiceUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.fallback;
+
+import com.baeldung.fallback.messaging.DevelopmentMessagingService;
+import com.baeldung.fallback.messaging.FallbackMessagingService;
+import com.baeldung.fallback.messaging.MessagingService;
+import com.baeldung.fallback.messaging.ProductionMessagingService;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = {FallbackMessagingService.class, DevelopmentMessagingService.class, ProductionMessagingService.class})
+public class DevelopmentMessagingServiceUnitTest {
+
+    @Autowired
+    private MessagingService messagingService;
+
+    @Test
+    public void givenNoProfile_whenSendMessage_thenDevelopmentMessagingService() {
+        assertEquals(messagingService.getClass(), DevelopmentMessagingService.class);
+    }
+}

spring-boot-modules/spring-boot-3/src/test/java/com/baeldung/fallback/FallbackMessagingServiceUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.fallback;
+
+import com.baeldung.fallback.messaging.DevelopmentMessagingService;
+import com.baeldung.fallback.messaging.FallbackMessagingService;
+import com.baeldung.fallback.messaging.MessagingService;
+import com.baeldung.fallback.messaging.ProductionMessagingService;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = {FallbackMessagingService.class, DevelopmentMessagingService.class, ProductionMessagingService.class})
+@ActiveProfiles("test")
+public class FallbackMessagingServiceUnitTest {
+
+    @Autowired
+    private MessagingService messagingService;
+
+    @Test
+    public void givenTestProfile_whenSendMessage_thenFallbackMessagingService() {
+        assertEquals(messagingService.getClass(), FallbackMessagingService.class);
+    }
+}

spring-boot-modules/spring-boot-3/src/test/java/com/baeldung/fallback/ProductionMessagingServiceUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.fallback;
+
+import com.baeldung.fallback.messaging.DevelopmentMessagingService;
+import com.baeldung.fallback.messaging.FallbackMessagingService;
+import com.baeldung.fallback.messaging.MessagingService;
+import com.baeldung.fallback.messaging.ProductionMessagingService;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = {FallbackMessagingService.class, DevelopmentMessagingService.class, ProductionMessagingService.class})
+@ActiveProfiles("production")
+public class ProductionMessagingServiceUnitTest {
+
+    @Autowired
+    private MessagingService messagingService;
+
+    @Test
+    public void givenProductionProfile_whenSendMessage_thenProductionMessagingService() {
+        assertEquals(messagingService.getClass(), ProductionMessagingService.class);
+    }
+}