[BAEL-7868] Autowiring an interface with multiple implementations

spring-di-4/pom.xml

@@ -33,6 +33,14 @@
                     <mainClass>com.baeldung.registrypostprocessor.RegistryPostProcessorApplication</mainClass>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>17</source>
+                    <target>17</target>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 </project>

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodService.java

@@ -0,0 +1,6 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+public interface GoodService {
+
+    String getHelloMessage();
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodServiceA.java

@@ -0,0 +1,18 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.context.annotation.Profile;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Service;
+
+@Service
+@Profile("default")
+@Qualifier("goodServiceA-custom-name")
+@Order(3)
+public class GoodServiceA implements GoodService {
+
+    @Override
+    public String getHelloMessage() {
+        return "Hello from A!";
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodServiceB.java

@@ -0,0 +1,16 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+import org.springframework.context.annotation.Profile;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Service;
+
+@Service
+@Profile("default")
+@Order(2)
+public class GoodServiceB implements GoodService {
+
+    @Override
+    public String getHelloMessage() {
+        return "Hello from B!";
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodServiceC.java

@@ -0,0 +1,18 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+import org.springframework.context.annotation.Primary;
+import org.springframework.context.annotation.Profile;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Service;
+
+@Primary
+@Service
+@Profile("default")
+@Order(1)
+public class GoodServiceC implements GoodService {
+
+    @Override
+    public String getHelloMessage() {
+        return "Hello from C!";
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodServiceD.java

@@ -0,0 +1,13 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+
+@Service
+@Profile("dev")
+public class GoodServiceD implements GoodService {
+
+    public String getHelloMessage() {
+        return "Hello from D!";
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/candidates/GoodServiceE.java

@@ -0,0 +1,14 @@
+package com.baeldung.autowiremultipleimplementations.candidates;
+
+import com.baeldung.autowiremultipleimplementations.condition.OnFeatureEnabledCondition;
+import org.springframework.context.annotation.Conditional;
+import org.springframework.stereotype.Service;
+
+@Service
+@Conditional(OnFeatureEnabledCondition.class)
+public class GoodServiceE implements GoodService {
+
+    public String getHelloMessage() {
+        return "Hello from E!";
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/components/CollectionsAutowire.java

@@ -0,0 +1,35 @@
+package com.baeldung.autowiremultipleimplementations.components;
+
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import java.util.Map;
+import java.util.Set;
+
+@Component
+public class CollectionsAutowire {
+
+    private final Set<GoodService> goodServices;
+    private final Map<String, GoodService> goodServiceMap;
+
+    @Autowired
+    public CollectionsAutowire(Set<GoodService> goodServices, Map<String, GoodService> goodServiceMap) {
+        this.goodServices = goodServices;
+        this.goodServiceMap = goodServiceMap;
+    }
+
+    public String hello() {
+        return goodServices.stream()
+                .map(GoodService::getHelloMessage)
+                .reduce((a, b) -> a + " " + b)
+                .orElse("No services available");
+    }
+
+    public String helloMap() {
+        return goodServiceMap.values().stream()
+                .map(GoodService::getHelloMessage)
+                .reduce((a, b) -> a + " " + b)
+                .orElse("No services available");
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/components/PrimaryAutowire.java

@@ -0,0 +1,20 @@
+package com.baeldung.autowiremultipleimplementations.components;
+
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class PrimaryAutowire {
+
+    private final GoodService goodService;
+
+    @Autowired
+    public PrimaryAutowire(GoodService goodService) {
+        this.goodService = goodService;
+    }
+
+    public String hello() {
+        return goodService.getHelloMessage();
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/components/QualifierAutowire.java

@@ -0,0 +1,29 @@
+package com.baeldung.autowiremultipleimplementations.components;
+
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.stereotype.Component;
+
+@Component
+public class QualifierAutowire {
+
+    private final GoodService goodServiceA;
+    private final GoodService goodServiceB;
+    private final GoodService goodServiceC;
+
+    @Autowired
+    public QualifierAutowire(@Qualifier("goodServiceA-custom-name") GoodService niceServiceA,
+                             @Qualifier("goodServiceB") GoodService niceServiceB,
+                             GoodService goodServiceC) {
+        this.goodServiceA = niceServiceA;
+        this.goodServiceB = niceServiceB;
+        this.goodServiceC = goodServiceC;
+    }
+
+    public String hello() {
+        return goodServiceA.getHelloMessage() + " " +
+                goodServiceB.getHelloMessage() + " " +
+                goodServiceC.getHelloMessage();
+    }
+}

spring-di-4/src/main/java/com/baeldung/autowiremultipleimplementations/condition/OnFeatureEnabledCondition.java

@@ -0,0 +1,14 @@
+package com.baeldung.autowiremultipleimplementations.condition;
+
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+public class OnFeatureEnabledCondition implements Condition {
+
+    @Override
+    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+        String featureToggle = context.getEnvironment().getProperty("feature.toggle");
+        return "enabled".equalsIgnoreCase(featureToggle);
+    }
+}

spring-di-4/src/test/java/com/baeldung/autowiremultipleimplementations/CollectionsAutowireUnitTest.java

@@ -0,0 +1,75 @@
+package com.baeldung.autowiremultipleimplementations;
+
+import com.baeldung.autowiremultipleimplementations.components.CollectionsAutowire;
+import com.baeldung.autowiremultipleimplementations.candidates.*;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(classes = {CollectionsAutowire.class, GoodServiceD.class, GoodServiceC.class, GoodServiceB.class, GoodServiceA.class})
+public class CollectionsAutowireUnitTest {
+
+    @Autowired
+    private CollectionsAutowire collectionsAutowire;
+
+    @Test
+    public void testSetAutowiring() throws NoSuchFieldException, IllegalAccessException {
+        Set<?> rawServices = (Set<?>) getPrivateField(collectionsAutowire, "goodServices");
+        assertNotNull(rawServices, "Set of GoodService should not be null");
+        assertFalse(rawServices.isEmpty(), "Set of GoodService should not be empty");
+
+        Set<GoodService> services = rawServices.stream()
+                .map(service -> (GoodService) service)
+                .filter(Objects::nonNull)
+                .collect(Collectors.toSet());
+
+        // Check for all specific types
+        assertTrue(services.stream().anyMatch(s -> s instanceof GoodServiceA), "Should contain GoodServiceA");
+        assertTrue(services.stream().anyMatch(s -> s instanceof GoodServiceB), "Should contain GoodServiceB");
+        assertTrue(services.stream().anyMatch(s -> s instanceof GoodServiceC), "Should contain GoodServiceC");
+
+        String actualMessage = collectionsAutowire.hello();
+        assertTrue(actualMessage.contains("Hello from A!"), "Message should contain greeting from A");
+        assertTrue(actualMessage.contains("Hello from B!"), "Message should contain greeting from B");
+        assertTrue(actualMessage.contains("Hello from C!"), "Message should contain greeting from C");
+    }
+
+    @Test
+    public void testMapAutowiring() throws NoSuchFieldException, IllegalAccessException {
+        Map<?, ?> rawServiceMap = (Map<?, ?>) getPrivateField(collectionsAutowire, "goodServiceMap");
+        assertNotNull(rawServiceMap, "Map of GoodService should not be null");
+        assertFalse(rawServiceMap.isEmpty(), "Map of GoodService should not be empty");
+
+        Map<String, GoodService> serviceMap = rawServiceMap.entrySet().stream()
+                .collect(Collectors.toMap(
+                        entry -> (String) entry.getKey(),
+                        entry -> (GoodService) entry.getValue()
+                ));
+
+        // Check keys and specific instances
+        assertTrue(serviceMap.containsKey("goodServiceA"), "Map should contain a key for GoodServiceA");
+        assertTrue(serviceMap.containsKey("goodServiceB"), "Map should contain a key for GoodServiceB");
+        assertTrue(serviceMap.containsKey("goodServiceC"), "Map should contain a key for GoodServiceC");
+
+        assertInstanceOf(GoodServiceA.class, serviceMap.get("goodServiceA"), "goodServiceA should be an instance of GoodServiceA");
+        assertInstanceOf(GoodServiceB.class, serviceMap.get("goodServiceB"), "goodServiceB should be an instance of GoodServiceB");
+        assertInstanceOf(GoodServiceC.class, serviceMap.get("goodServiceC"), "goodServiceC should be an instance of GoodServiceC");
+    }
+
+    private Object getPrivateField(Object object, String fieldName) throws NoSuchFieldException, IllegalAccessException {
+        Field field = object.getClass().getDeclaredField(fieldName);
+        field.setAccessible(true);
+        return field.get(object);
+    }
+}

spring-di-4/src/test/java/com/baeldung/autowiremultipleimplementations/ConditionalDisabledUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.autowiremultipleimplementations;
+
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodServiceE;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(classes = {GoodServiceE.class})
+@TestPropertySource(properties = {"feature.toggle=disabled"})
+public class ConditionalDisabledUnitTest {
+
+    @Autowired(required = false)
+    private GoodService goodService;
+
+    @Test
+    void testServiceWhenFeatureDisabled() {
+        assertNull(goodService, "GoodService should not be autowired when feature.toggle is disabled");
+    }
+}

spring-di-4/src/test/java/com/baeldung/autowiremultipleimplementations/ConditionalEnabledUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.autowiremultipleimplementations;
+
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodServiceE;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(classes = {GoodServiceE.class})
+@TestPropertySource(properties = {"feature.toggle=enabled"})
+public class ConditionalEnabledUnitTest {
+
+    @Autowired
+    private GoodService goodService;
+
+    @Test
+    void testServiceWhenFeatureEnabled() {
+        assertNotNull(goodService, "GoodService should be autowired when feature.toggle is enabled");
+        assertInstanceOf(GoodServiceE.class, goodService, "goodService should be an instance of GoodServiceE");
+    }
+}

spring-di-4/src/test/java/com/baeldung/autowiremultipleimplementations/PrimaryAutowireUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.autowiremultipleimplementations;
+
+import com.baeldung.autowiremultipleimplementations.components.PrimaryAutowire;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodService;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodServiceA;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodServiceB;
+import com.baeldung.autowiremultipleimplementations.candidates.GoodServiceC;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@SpringBootTest(classes = {PrimaryAutowire.class, GoodServiceC.class, GoodServiceB.class, GoodServiceA.class})
+@ExtendWith(SpringExtension.class)
+public class PrimaryAutowireUnitTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Autowired
+    private PrimaryAutowire primaryAutowire;
+
+    @Test
+    public void whenPrimaryServiceInjected_thenItShouldBeGoodServiceC() {
+        GoodService injectedService = context.getBean(GoodService.class);
+
+        assertInstanceOf(GoodServiceC.class, injectedService);
+
+        String expectedMessage = "Hello from C!"; // GoodServiceC returns this message
+        String actualMessage = primaryAutowire.hello();
+
+        assertEquals(expectedMessage, actualMessage);
+    }
+}