Different Types of Bean Injection in Spring

spring-core/src/main/java/com/baeldung/beansinjectiontypes/Cabriolet.java

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+package com.baeldung.beansinjectiontypes;
+
+public class Cabriolet implements Car{
+    
+    public void honk(){
+        System.out.println("I'm a cabriolet!");
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/Car.java

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+package com.baeldung.beansinjectiontypes;
+
+public interface Car {
+
+    public void honk();
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/DealershipTraditionalStyle.java

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+package com.baeldung.beansinjectiontypes;
+
+public class DealershipTraditionalStyle {
+    private Car car = new Sedan();
+
+    public Car getCar() {
+        return car;
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/DealershipWithDependenciesInjection.java

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+package com.baeldung.beansinjectiontypes;
+
+public class DealershipWithDependenciesInjection {
+    private Car car;
+
+    public DealershipWithDependenciesInjection(Car car) {
+        this.car = car;
+    }
+
+    public Car getCar() {
+        return car;
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/Sedan.java

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+package com.baeldung.beansinjectiontypes;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Sedan implements Car {
+    public void honk(){
+        System.out.println("I'm a sedan!");
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/constructor/Config.java

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+package com.baeldung.beansinjectiontypes.constructor;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.beansinjectiontypes.Car;
+import com.baeldung.beansinjectiontypes.Sedan;
+
+@Configuration(value="constructorConfig")
+public class Config {
+    @Bean
+    public Car car() {
+        return new Sedan();
+    }
+
+    @Bean
+    public Dealership dealership() {
+        return new Dealership(car());
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/constructor/Dealership.java

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+package com.baeldung.beansinjectiontypes.constructor;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import com.baeldung.beansinjectiontypes.Car;
+
+@Component(value="constructorDealership")
+public class Dealership {
+    private Car car;
+
+    @Autowired
+    public Dealership(Car car) {
+        this.car = car;
+    }
+
+    public Car getCar() {
+        return car;
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/constructor/HornCheckerFile.java

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+package com.baeldung.beansinjectiontypes.constructor;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+public class HornCheckerFile {
+
+    public static void main(String[] args) {
+        try (AnnotationConfigApplicationContext context = 
+          new AnnotationConfigApplicationContext(Config.class)) {
+            Dealership dealership = (Dealership) context.getBean("dealership");
+
+            dealership.getCar().honk();
+        }
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/constructor/HornCheckerXML.java

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+package com.baeldung.beansinjectiontypes.constructor;
+
+import org.springframework.context.support.FileSystemXmlApplicationContext;
+
+public class HornCheckerXML {
+
+    public static void main(String[] args) {
+        try (FileSystemXmlApplicationContext context = 
+              new FileSystemXmlApplicationContext("src/main/resources/beansinjectiontypes-ctx.xml")) {
+            Dealership dealership = (Dealership) context.getBean("constructorDealership");
+
+            dealership.getCar().honk();
+        }
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/setter/Config.java

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+package com.baeldung.beansinjectiontypes.setter;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.beansinjectiontypes.Car;
+import com.baeldung.beansinjectiontypes.Sedan;
+
+@Configuration(value="setterConfig")
+public class Config {
+    @Bean
+    public Car car() {
+        return new Sedan();
+    }
+
+    @Bean
+    public Dealership dealership() {
+        Dealership dealership = new Dealership();
+        dealership.setCar(car());
+        return dealership;
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/setter/Dealership.java

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+package com.baeldung.beansinjectiontypes.setter;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import com.baeldung.beansinjectiontypes.Car;
+
+@Component(value="setterDealership")
+public class Dealership {
+    private Car car;
+
+    @Autowired
+    public void setCar(Car car) {
+        this.car = car;
+    }
+    public Car getCar() {
+        return car;
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/setter/HornCheckerFile.java

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+package com.baeldung.beansinjectiontypes.setter;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+public class HornCheckerFile {
+
+    public static void main(String[] args) {
+        try (AnnotationConfigApplicationContext context = 
+          new AnnotationConfigApplicationContext(Config.class)) {
+            Dealership dealership = (Dealership) context.getBean("dealership");
+
+            dealership.getCar().honk();
+        }
+    }
+}

spring-core/src/main/java/com/baeldung/beansinjectiontypes/setter/HornCheckerXML.java

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+package com.baeldung.beansinjectiontypes.setter;
+
+import org.springframework.context.support.FileSystemXmlApplicationContext;
+
+public class HornCheckerXML {
+
+    public static void main(String[] args) {
+        try (FileSystemXmlApplicationContext context = 
+              new FileSystemXmlApplicationContext("src/main/resources/beansinjectiontypes-ctx.xml")) {
+            Dealership dealership = (Dealership) context.getBean("setterDealership");
+
+            dealership.getCar().honk();
+        }
+    }
+}

spring-core/src/main/resources/beansinjectiontypes-ctx.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
+	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
+	xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"
+	xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd">
+
+	<context:component-scan base-package="com.baeldung.beansinjectiontypes" />
+
+</beans>

spring-core/src/test/java/com/baeldung/beansinjectiontypes/BeansInjectionTypesIntegrationTest.java

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+package com.baeldung.beansinjectiontypes;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.FileSystemXmlApplicationContext;
+
+import com.baeldung.beansinjectiontypes.constructor.Config;
+import com.baeldung.beansinjectiontypes.constructor.Dealership;
+
+public class BeansInjectionTypesIntegrationTest {
+
+    @Test
+    public void configBean_WhenSetOnConstructor_ThenDependencyValid() {
+        try (AnnotationConfigApplicationContext context = 
+          new AnnotationConfigApplicationContext(Config.class)) {
+            Dealership dealership = (Dealership) context.getBean("dealership");
+
+            assertTrue(dealership.getCar() instanceof Sedan);
+        }
+    }
+
+    @Test
+    public void configBean_WhenSetOnSetter_ThenDependencyValid() {
+        try (AnnotationConfigApplicationContext context = 
+          new AnnotationConfigApplicationContext(com.baeldung.beansinjectiontypes.setter.Config.class)) {
+            com.baeldung.beansinjectiontypes.setter.Dealership dealership = 
+              (com.baeldung.beansinjectiontypes.setter.Dealership) context.getBean("dealership");
+
+            assertTrue(dealership.getCar() instanceof Sedan);
+        }        
+    }
+
+    @Test
+    public void annotationAndXML_WhenSetOnSetter_ThenDependencyValid() {
+        try (FileSystemXmlApplicationContext context = 
+          new FileSystemXmlApplicationContext("src/main/resources/beansinjectiontypes-ctx.xml")) {
+            Dealership dealership = (Dealership) context.getBean("constructorDealership");
+
+            assertTrue(dealership.getCar() instanceof Sedan);
+        }        
+    }
+
+    @Test
+    public void annotationAndXML_WhenSetOnConstructor_ThenDependencyValid() {
+        try (FileSystemXmlApplicationContext context = 
+          new FileSystemXmlApplicationContext("src/main/resources/beansinjectiontypes-ctx.xml")) {
+            com.baeldung.beansinjectiontypes.setter.Dealership dealership = 
+                (com.baeldung.beansinjectiontypes.setter.Dealership) context.getBean("setterDealership");
+
+            assertTrue(dealership.getCar() instanceof Sedan);
+        }        
+    }
+
+}