Christopher Franklin Different Types of Bean Injection in Spring

My first article about the three different types of bean injection
supported by the Spring Framework. This code walks through all three
methods and has supporting tests.

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

@@ -0,0 +1,16 @@
+package com.baeldung.beaninjectiontypes;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.beaninjectiontypes")
+public class Config {
+
+    @Bean
+    public ExampleService exampleService() {
+        return new ExampleService();
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/ExampleService.java

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+package com.baeldung.beaninjectiontypes;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleService {
+
+    public String getExampleText() {
+        return "Example";
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/ExampleWithConstructorInjection.java

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+package com.baeldung.beaninjectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleWithConstructorInjection {
+
+    private ExampleService exampleService;
+
+    @Autowired
+    public ExampleWithConstructorInjection(ExampleService exampleService) {
+        this.exampleService = exampleService;
+    }
+
+    public String verifyInjection() {
+        return this.exampleService.getExampleText();
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/ExampleWithPropertyInjection.java

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+package com.baeldung.beaninjectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleWithPropertyInjection {
+
+    @Autowired
+    private ExampleService exampleService;
+
+    public String verifyInjection() {
+        return this.exampleService.getExampleText();
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjectiontypes/ExampleWithSetterInjection.java

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+package com.baeldung.beaninjectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleWithSetterInjection {
+
+    private ExampleService exampleService;
+
+    @Autowired
+    public void setExampleService(ExampleService exampleService) {
+        this.exampleService = exampleService;
+    }
+
+    public String verifyInjection() {
+        return this.exampleService.getExampleText();
+    }
+
+}

spring-core/src/test/java/com/baeldung/beaninjectiontypes/BeanInjectionTest.java

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+package com.baeldung.beaninjectiontypes;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(loader = AnnotationConfigContextLoader.class, classes = Config.class)
+public class BeanInjectionTest {
+
+    @Test
+    public void whenConstructorInjection_ThenBeanValid() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+        ExampleWithConstructorInjection exampleBean = context.getBean(ExampleWithConstructorInjection.class);
+
+        assertEquals("Example", exampleBean.verifyInjection());
+    }
+
+    @Test
+    public void whenSetterInjection_ThenBeanValid() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+        ExampleWithSetterInjection exampleBean = context.getBean(ExampleWithSetterInjection.class);
+
+        assertEquals("Example", exampleBean.verifyInjection());
+    }
+
+    @Test
+    public void whenProperyInjection_ThenBeanValid() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+        ExampleWithPropertyInjection exampleBean = context.getBean(ExampleWithPropertyInjection.class);
+
+        assertEquals("Example", exampleBean.verifyInjection());
+    }
+
+}