Constructor and setter based Dependency injection code example

spring-boot/dependency-injection/src/main/java/com/example/ExampleApplicationCI.java

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+package com.example;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+
+import com.example.constructorinjection.Cake;
+
+@SpringBootApplication(scanBasePackages= {"com.example.constructorinjection","com.example.dependency"})
+public class ExampleApplicationCI  {
+
+	private static Logger LOGGER=LoggerFactory.getLogger(ExampleApplicationCI.class);
+	public static void main(String[] args) {
+		
+		ApplicationContext context = SpringApplication.run(ExampleApplicationCI.class, args);
+		Cake obj = context.getBean(Cake.class);
+		LOGGER.info("Cake : "+ obj.toString());
+	}
+
+}

spring-boot/dependency-injection/src/main/java/com/example/ExampleApplicationSI.java

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+package com.example;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+
+import com.example.setterinjection.Cake;
+
+@SpringBootApplication(scanBasePackages= {"com.example.setterinjection","com.example.dependency"})
+public class ExampleApplicationSI  {
+
+	private static Logger LOGGER=LoggerFactory.getLogger(ExampleApplicationSI.class);
+	public static void main(String[] args) {
+		
+		ApplicationContext context = SpringApplication.run(ExampleApplicationSI.class, args);
+		Cake obj = context.getBean(Cake.class);
+		LOGGER.info("Cake : "+ obj.toString());
+	}
+
+}

spring-boot/dependency-injection/src/main/java/com/example/constructorinjection/Cake.java

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+package com.example.constructorinjection;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+
+import com.example.dependency.Flavor;
+
+
+@Component
+public class Cake {
+
+	private static Logger LOGGER = LoggerFactory.getLogger(Cake.class);
+
+
+	private Flavor flavor;
+
+	public Cake(Flavor flavor) throws IllegalAccessException {
+		
+		//check if the required dependency is not null
+		if (flavor != null) {
+			this.flavor = flavor;
+			LOGGER.info("Flavor from Constructor Injection : " + flavor);
+		} else {
+			throw new IllegalArgumentException("Cake cannot be created with null flavor object");
+		}
+	}
+
+	public Flavor getFlavor() {
+		return flavor;
+	}
+	
+	@Override
+	public String toString() {
+		return "Cake [flavor=" + flavor + "]";
+	}
+
+}

spring-boot/dependency-injection/src/main/java/com/example/dependency/Flavor.java

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+package com.example.dependency;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Flavor {
+	
+	String flavorType = " Chocolate ";
+	String color = " White ";
+	
+	public String getFlavorType() {
+		return flavorType;
+	}
+	
+	public String getColor() {
+		return color;
+	}
+
+	@Override
+	public String toString() {
+		return "Flavor [flavorType=" + flavorType + ", color=" + color + "]";
+	}
+	
+
+}

spring-boot/dependency-injection/src/main/java/com/example/dependency/Topping.java

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+package com.example.dependency;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Topping {
+
+	private String toppingName;
+
+	public String getToppingName() {
+		return toppingName;
+	}
+
+	public void setToppingName(String toppingName) {
+		this.toppingName = toppingName;
+	}
+
+	@Override
+	public String toString() {
+		return "Topping [toppingName=" + toppingName + "]";
+	}
+
+
+}

spring-boot/dependency-injection/src/main/java/com/example/setterinjection/Cake.java

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+package com.example.setterinjection;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import com.example.dependency.Flavor;
+import com.example.dependency.Topping;
+
+@Component
+public class Cake {
+
+	private Logger LOGGER = LoggerFactory.getLogger(Cake.class);
+	
+	private Flavor flavor;
+	
+	@Autowired
+	private Topping toppings;
+	
+	public Cake() {
+		LOGGER.info("Flavor from setter Injection : " + this.flavor);
+	}
+	
+	@Autowired
+	public void setFlavor(Flavor flavor) {
+		LOGGER.info("Initialising flavor object using setter injection");
+		this.flavor = flavor;
+	}
+
+	public Flavor getFlavor() {
+		return flavor;
+	}
+
+	public Topping getToppings() {
+		return toppings;
+	}
+
+	public void setToppings(Topping toppings) {
+		this.toppings = toppings;
+	}
+
+	@Override
+	public String toString() {
+		return "Cake [LOGGER=" + LOGGER + ", flavor=" + flavor + ", toppings=" + toppings + "]";
+	}
+
+
+
+}

spring-boot/dependency-injection/src/main/resources/application.properties

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+spring.main.web-application-type=none
+spring.main.banner-mode=off

spring-boot/dependency-injection/src/test/java/com/example/test/constructorinjection/TestCakeClassConstructorInjection.java

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+package com.example.test.constructorinjection;
+
+import org.junit.Assert;
+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.SpringJUnit4ClassRunner;
+
+import com.example.ExampleApplicationCI;
+import com.example.constructorinjection.Cake;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringBootTest(classes = ExampleApplicationCI.class)
+public class TestCakeClassConstructorInjection {
+
+	@Autowired
+	Cake cake;
+	
+	@Test
+	public void testConstructorInjection() {	
+		String testColor=cake.getFlavor().getColor();
+		Assert.assertEquals(testColor, " White ");
+	}
+}

spring-boot/dependency-injection/src/test/java/com/example/test/setterinjection/TestCakeClassSetterInjection.java

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+package com.example.test.setterinjection;
+
+import org.junit.Assert;
+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.SpringJUnit4ClassRunner;
+
+import com.example.ExampleApplicationSI;
+import com.example.setterinjection.Cake;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringBootTest(classes = ExampleApplicationSI.class)
+public class TestCakeClassSetterInjection {
+
+	@Autowired
+	Cake cake;
+
+	@Test
+	public void testSetterInjection() {
+		String testColor = cake.getFlavor().getColor();
+		Assert.assertEquals(testColor, " White ");
+		String toppingsName=cake.getToppings().getToppingName();
+		
+		//check if the dependency is not null
+		if(toppingsName!=null) {
+			Assert.assertEquals(toppingsName, "gems");
+		}
+		
+	}
+}