adding manual DI example

src/main/java/guru/springframework/sfgdi/controllers/ConstructorInjectedController.java

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+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingService;
+
+/**
+ * Created by jt on 12/26/19.
+ */
+public class ConstructorInjectedController {
+    private final GreetingService greetingService;
+
+    public ConstructorInjectedController(GreetingService greetingService) {
+        this.greetingService = greetingService;
+    }
+
+    public String getGreeting(){
+        return greetingService.sayGreeting();
+    }
+}

src/main/java/guru/springframework/sfgdi/controllers/PropertyInjectedController.java

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+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingService;
+
+/**
+ * Created by jt on 12/26/19.
+ */
+public class PropertyInjectedController {
+
+    public GreetingService greetingService;
+
+    public String getGreeting(){
+        return greetingService.sayGreeting();
+    }
+
+}

src/main/java/guru/springframework/sfgdi/controllers/SetterInjectedController.java

@@ -0,0 +1,19 @@
+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingService;
+
+/**
+ * Created by jt on 12/26/19.
+ */
+public class SetterInjectedController {
+
+    private GreetingService greetingService;
+
+    public void setGreetingService(GreetingService greetingService) {
+        this.greetingService = greetingService;
+    }
+
+    public String getGreeting(){
+        return greetingService.sayGreeting();
+    }
+}

src/main/java/guru/springframework/sfgdi/services/GreetingService.java

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+package guru.springframework.sfgdi.services;
+
+/**
+ * Created by jt on 12/26/19.
+ */
+public interface GreetingService {
+
+    String sayGreeting();
+}

src/main/java/guru/springframework/sfgdi/services/GreetingServiceImpl.java

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+package guru.springframework.sfgdi.services;
+
+/**
+ * Created by jt on 12/26/19.
+ */
+public class GreetingServiceImpl implements GreetingService {
+    @Override
+    public String sayGreeting() {
+        return "Hello World";
+    }
+}

src/test/java/guru/springframework/sfgdi/controllers/ConstructorInjectedControllerTest.java

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+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingServiceImpl;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ConstructorInjectedControllerTest {
+
+    ConstructorInjectedController controller;
+
+    @BeforeEach
+    void setUp() {
+        controller = new ConstructorInjectedController(new GreetingServiceImpl());
+    }
+
+    @Test
+    void getGreeting() {
+
+        System.out.println(controller.getGreeting());
+
+    }
+}

src/test/java/guru/springframework/sfgdi/controllers/PropertyInjectedControllerTest.java

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+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingServiceImpl;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PropertyInjectedControllerTest {
+
+    PropertyInjectedController controller;
+
+    @BeforeEach
+    void setUp() {
+        controller = new PropertyInjectedController();
+
+        controller.greetingService = new GreetingServiceImpl();
+    }
+
+    @Test
+    void getGreeting() {
+
+        System.out.println(controller.getGreeting());
+    }
+}

src/test/java/guru/springframework/sfgdi/controllers/SetterInjectedControllerTest.java

@@ -0,0 +1,24 @@
+package guru.springframework.sfgdi.controllers;
+
+import guru.springframework.sfgdi.services.GreetingServiceImpl;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SetterInjectedControllerTest {
+
+    SetterInjectedController controller;
+
+    @BeforeEach
+    void setUp() {
+        controller = new SetterInjectedController();
+        controller.setGreetingService(new GreetingServiceImpl());
+    }
+
+    @Test
+    void getGreeting() {
+        System.out.println(controller.getGreeting());
+
+    }
+}