Basic implementation showing the DI types in Spring - with tests

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

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+package com.baeldung.injectiontypes;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.injectiontypes")
+public class Config {
+    @Bean
+    public Hospital hospital() {
+        return new Hospital();
+    }
+}

spring-core/src/main/java/com/baeldung/injectiontypes/Doctor.java

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+package com.baeldung.injectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class Doctor {
+    private Hospital hospital;
+
+    @Autowired
+    public Doctor(Hospital hospital) {
+        this.hospital = hospital;
+    }
+
+    public Hospital getHospital() {
+        return hospital;
+    }
+}

spring-core/src/main/java/com/baeldung/injectiontypes/Hospital.java

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+package com.baeldung.injectiontypes;
+
+public class Hospital {
+    //TODO
+}

spring-core/src/main/java/com/baeldung/injectiontypes/Nurse.java

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+package com.baeldung.injectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class Nurse {
+    private Hospital hospital;
+
+    public Nurse() {
+        //TODO
+    }
+
+    public Hospital getHospital() {
+        return hospital;
+    }
+
+    @Autowired
+    public void setHospital(Hospital hospital) {
+        this.hospital = hospital;
+    }
+}

spring-core/src/main/java/com/baeldung/injectiontypes/Surgeon.java

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+package com.baeldung.injectiontypes;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class Surgeon {
+    @Autowired
+    private Hospital hospital;
+
+    public Surgeon() {
+        //TODO
+    }
+
+    public Hospital getHospital() {
+        return hospital;
+    }
+}

spring-core/src/test/java/com/baeldung/injectiontypes/DoctorTest.java

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+package com.baeldung.injectiontypes;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+import static org.junit.Assert.assertNotNull;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(
+        loader = AnnotationConfigContextLoader.class,
+        classes = Config.class)
+public class DoctorTest {
+    @Autowired
+    private Doctor doctor;
+
+    @Test
+    public void givenDoctor_whenInitialised_thenHospitalSet() throws Exception {
+        assertNotNull(doctor.getHospital());
+    }
+}

spring-core/src/test/java/com/baeldung/injectiontypes/NurseTest.java

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+package com.baeldung.injectiontypes;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+import static org.junit.Assert.*;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(
+        loader = AnnotationConfigContextLoader.class,
+        classes = Config.class)
+public class NurseTest {
+    @Autowired
+    private Nurse nurse;
+
+    @Test
+    public void givenNurse_whenInitialised_thenHospitalSet() throws Exception {
+        assertNotNull(nurse.getHospital());
+    }
+}

spring-core/src/test/java/com/baeldung/injectiontypes/SurgeonTest.java

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+package com.baeldung.injectiontypes;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+import static org.junit.Assert.*;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(
+        loader = AnnotationConfigContextLoader.class,
+        classes = Config.class)
+public class SurgeonTest {
+    @Autowired
+    private Surgeon surgeon;
+
+    @Test
+    public void givenSurgeon_whenInitialised_thenHospitalSet() throws Exception {
+        assertNotNull(surgeon.getHospital());
+    }
+}