Code for Alessio Stalla's evaluation article (Different Types of Bean Injection in Spring)

spring-core/src/main/java/com/baeldung/typesofbeaninjection/Config.java

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+package com.baeldung.typesofbeaninjection;
+
+import com.baeldung.typesofbeaninjection.domain.Engine;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.typesofbeaninjection")
+public class Config {
+
+    @Bean
+    public Engine engine() {
+        return new Engine("V8", 5);
+    }
+}

spring-core/src/main/java/com/baeldung/typesofbeaninjection/domain/Car.java

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+package com.baeldung.typesofbeaninjection.domain;
+
+public class Car {
+    private Engine engine;
+
+    public Car() {}
+
+    public Car(Engine engine) {
+        this.engine = engine;
+    }
+
+    public Engine getEngine() {
+        return engine;
+    }
+
+    public void setEngine(Engine engine) {
+        this.engine = engine;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Car with %s engine", engine);
+    }
+}

spring-core/src/main/java/com/baeldung/typesofbeaninjection/domain/Engine.java

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+package com.baeldung.typesofbeaninjection.domain;
+
+public class Engine {
+    private final String type;
+    private final int volume;
+
+    public Engine(String type, int volume) {
+        this.type = type;
+        this.volume = volume;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public int getVolume() {
+        return volume;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s %d", type, volume);
+    }
+}

spring-core/src/main/java/com/baeldung/typesofbeaninjection/domain/autowired/constructor/Car.java

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+package com.baeldung.typesofbeaninjection.domain.autowired.constructor;
+
+import com.baeldung.typesofbeaninjection.domain.Engine;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component("car-autowired-by-constructor")
+public class Car {
+    private Engine engine;
+
+    public Car() {}
+
+    @Autowired
+    public Car(Engine engine) {
+        this.engine = engine;
+    }
+
+    public Engine getEngine() {
+        return engine;
+    }
+
+    public void setEngine(Engine engine) {
+        this.engine = engine;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Car with %s engine", engine);
+    }
+}

spring-core/src/main/java/com/baeldung/typesofbeaninjection/domain/autowired/properties/Car.java

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+package com.baeldung.typesofbeaninjection.domain.autowired.properties;
+
+import com.baeldung.typesofbeaninjection.domain.Engine;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component("car-autowired-by-properties")
+public class Car {
+    private Engine engine;
+
+    public Car() {}
+
+    public Car(Engine engine) {
+        this.engine = engine;
+    }
+
+    public Engine getEngine() {
+        return engine;
+    }
+
+    @Autowired
+    public void setEngine(Engine engine) {
+        this.engine = engine;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Car with %s engine", engine);
+    }
+}

spring-core/src/main/resources/typesofbeaninjection-context.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns="http://www.springframework.org/schema/beans"
+       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
+
+    <bean name="engine" class="com.baeldung.typesofbeaninjection.domain.Engine">
+        <constructor-arg value="V8" />
+        <constructor-arg value="5" />
+    </bean>
+
+    <bean name="alices-car" class="com.baeldung.typesofbeaninjection.domain.Car">
+        <constructor-arg ref="engine" />
+    </bean>
+
+    <bean name="bobs-car" class="com.baeldung.typesofbeaninjection.domain.Car">
+        <property name="engine" ref="engine" />
+    </bean>
+
+</beans>

spring-core/src/test/java/com/baeldung/typesofbeaninjection/TypeOfBeanInjectionUnitTest.java

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+package com.baeldung.typesofbeaninjection;
+
+import com.baeldung.typesofbeaninjection.domain.Car;
+import com.baeldung.typesofbeaninjection.domain.Engine;
+import org.junit.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class TypeOfBeanInjectionUnitTest {
+
+    @Test
+    public void whenConstructionInjectionInXML_thenCarHasEngine() {
+        ApplicationContext applicationContext
+          = new ClassPathXmlApplicationContext("/typesofbeaninjection-context.xml");
+        Car car = applicationContext.getBean("alices-car", Car.class);
+
+        checkEngine(car.getEngine());
+    }
+
+    @Test
+    public void whenPropertyInjectionInXML_thenCarHasEngine() {
+        ApplicationContext applicationContext
+          = new ClassPathXmlApplicationContext("/typesofbeaninjection-context.xml");
+        Car car = applicationContext.getBean("bobs-car", Car.class);
+
+        checkEngine(car.getEngine());
+    }
+
+    @Test
+    public void whenConstructionInjectionAnnotations_thenCarHasEngine() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Config.class);
+        com.baeldung.typesofbeaninjection.domain.autowired.constructor.Car car
+          = applicationContext.getBean(com.baeldung.typesofbeaninjection.domain.autowired.constructor.Car.class);
+
+        checkEngine(car.getEngine());
+    }
+
+    @Test
+    public void whenPropertyInjectionAnnotations_thenCarHasEngine() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Config.class);
+        com.baeldung.typesofbeaninjection.domain.autowired.properties.Car car
+           = applicationContext.getBean(com.baeldung.typesofbeaninjection.domain.autowired.properties.Car.class);
+
+        checkEngine(car.getEngine());
+    }
+
+    private void checkEngine(Engine engine) {
+        assertNotNull(engine);
+        assertEquals("V8", engine.getType());
+        assertEquals(5, engine.getVolume());
+    }
+
+
+}