Types of Bean Injection in Spring

spring-core/src/main/java/com/baeldung/beaninjectiontypes/constructorinjection/Address.java

@@ -0,0 +1,22 @@
+package com.baeldung.beaninjectiontypes.constructorinjection;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Address {
+
+    private String city;
+
+    private String country;
+
+    public Address(String city, String country) {
+        this.city = city;
+        this.country = country;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s, %s", city, country);
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/constructorinjection/Config.java

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+package com.baeldung.beaninjectiontypes.constructorinjection;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.beaninjectiontypes.constructorinjection")
+public class Config {
+
+    @Bean
+    public Address address() {
+        return new Address("New York City", "USA");
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/constructorinjection/User.java

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+package com.baeldung.beaninjectiontypes.constructorinjection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class User {
+
+    private Address address;
+
+    @Autowired
+    public User(Address address) {
+        this.address = address;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("User Address: %s", address);
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/setterinjection/Address.java

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+package com.baeldung.beaninjectiontypes.setterinjection;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Address {
+
+    private String city;
+
+    private String country;
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s, %s", city, country);
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/setterinjection/Config.java

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+package com.baeldung.beaninjectiontypes.setterinjection;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.beaninjectiontypes.setterinjection")
+public class Config {
+
+    @Bean
+    public Address address() {
+        Address address = new Address();
+        address.setCity("Los Angeles");
+        address.setCountry("USA");
+        return address;
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/setterinjection/User.java

@@ -0,0 +1,21 @@
+package com.baeldung.beaninjectiontypes.setterinjection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class User {
+
+    private Address address;
+
+    @Autowired
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("User Address : %s", address);
+    }
+
+}

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

@@ -1,22 +1,23 @@
-<?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">
+<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://www.springframework.org/schema/beans
+    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
 
-	<bean id="exampleDAO" class="com.baeldung.beaninjection.ExampleDAOBean">
-		<constructor-arg index="0" type="java.lang.String"
-			value="Mandatory DAO Property X" />
-	</bean>
+    <bean id="userWithCI" class="com.baeldung.beaninjectiontypes.constructorinjection.User">
+        <constructor-arg ref="addressWithCI" />
+    </bean>
 
-	<bean id="anotherSampleDAO" class="com.baeldung.beaninjection.AnotherSampleDAOBean">
-		<constructor-arg index="0" type="java.lang.String"
-			value="Mandatory DAO Property Y" />
-	</bean>
+    <bean id="userWithSI" class="com.baeldung.beaninjectiontypes.setterinjection.User">
+        <property name="address" ref="addressWithSI" />
+    </bean>
 
-	<bean id="exampleService" class="com.baeldung.beaninjection.ExampleServiceBean">
-		<constructor-arg index="0" ref="exampleDAO" />
-		<property name="propertyX" value="Some Service Property X"></property>
-		<property name="anotherSampleDAO" ref="anotherSampleDAO"></property>
-	</bean>
+    <bean id="addressWithCI" class="com.baeldung.beaninjectiontypes.constructorinjection.Address">
+        <constructor-arg index="0" value="California"></constructor-arg>
+        <constructor-arg index="1" value="USA"></constructor-arg>
+    </bean>
+
+    <bean id="addressWithSI" class="com.baeldung.beaninjectiontypes.setterinjection.Address">
+        <property name="city" value="Washington D.C."></property>
+        <property name="country" value="USA"></property>
+    </bean>
 
 </beans>

spring-core/src/test/java/com/baeldung/beaninjectiontypes/constructorinjection/ConstructorInjectionTest.java

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+package com.baeldung.beaninjectiontypes.constructorinjection;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class ConstructorInjectionTest {
+
+    @Test
+    public void givenXMLConfiguration_WhenConstructorArgPassed_ThenDependencyValid() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("beaninjectiontypes-context.xml");
+        User user = (User) context.getBean("userWithCI");
+
+        String expectedOutput = "User Address: California, USA";
+
+        assertTrue(expectedOutput.equals(user.toString()));
+    }
+
+    @Test
+    public void givenPOJOConfiguration_WhenConstructorArgPassed_ThenDependencyValid() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+        User user = (User) context.getBean(User.class);
+
+        String expectedOutput = "User Address: New York City, USA";
+
+        assertTrue(expectedOutput.equals(user.toString()));
+    }
+
+}

spring-core/src/test/java/com/baeldung/beaninjectiontypes/setterinjection/SetterInjectionTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.beaninjectiontypes.setterinjection;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class SetterInjectionTest {
+
+    @Test
+    public void givenXMLConfiguration_WhenSetterArgPassed_ThenDependencyValid() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("beaninjectiontypes-context.xml");
+        User user = (User) context.getBean("userWithSI");
+
+        String expectedOutput = "User Address : Washington D.C., USA";
+
+        assertTrue(expectedOutput.equals(user.toString()));
+    }
+
+    @Test
+    public void givenPOJOConfiguration_WhenSetterArgPassed_ThenDependencyValid() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+        User user = (User) context.getBean(User.class);
+
+        String expectedOutput = "User Address : Los Angeles, USA";
+
+        assertTrue(expectedOutput.equals(user.toString()));
+    }
+
+}