added tests & changed configuration to Java-based config

spring-core/src/main/java/com/baeldung/ConstructorApp.java

@@ -1,15 +1,16 @@
 package com.baeldung;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 
+import com.baeldung.configuration.ConstructorConfig;
 import com.baeldung.model.Student;
 
 public class ConstructorApp {
     public static void main(String[] args) {
-        ApplicationContext context = new ClassPathXmlApplicationContext("constructor-context.xml");
-
-        Student student = (Student) context.getBean("student");
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ConstructorConfig.class);
+        Student student = context.getBean(Student.class);
         student.introduceMyself();
     }
 }

spring-core/src/main/java/com/baeldung/SetterApp.java

@@ -1,15 +1,13 @@
 package com.baeldung;
 
-import org.springframework.context.ApplicationContext;
-import org.springframework.context.support.ClassPathXmlApplicationContext;
-
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import com.baeldung.configuration.SetterConfig;
 import com.baeldung.model.Student;
 
 public class SetterApp {
     public static void main(String[] args) {
-        ApplicationContext context = new ClassPathXmlApplicationContext("setter-context.xml");
-
-        Student student = (Student) context.getBean("student");
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SetterConfig.class);
+        Student student = context.getBean(Student.class);
         student.introduceMyself();
     }
 }

spring-core/src/main/java/com/baeldung/configuration/ConstructorConfig.java

@@ -0,0 +1,21 @@
+package com.baeldung.configuration;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.model.College;
+import com.baeldung.model.Student;
+
+@Configuration
+public class ConstructorConfig {
+
+    @Bean
+    public Student student() {
+        return new Student(1, "John", college());
+    }
+
+    @Bean
+    public College college() {
+        return new College(1, "New York");
+    }
+}

spring-core/src/main/java/com/baeldung/configuration/SetterConfig.java

@@ -0,0 +1,28 @@
+package com.baeldung.configuration;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.model.College;
+import com.baeldung.model.Student;
+
+@Configuration
+public class SetterConfig {
+
+    @Bean
+    public Student student() {
+        Student student = new Student();
+        student.setId(2);
+        student.setName("Tom");
+        student.setCollege(college());
+        return student;
+    }
+
+    @Bean
+    public College college() {
+        College college = new College();
+        college.setId(2);
+        college.setName("Pittsburgh");
+        return college;
+    }
+}

spring-core/src/test/java/com/baeldung/configuration/ConstructorConfigTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.configuration;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import com.baeldung.model.Student;
+
+public class ConstructorConfigTest {
+
+    @Test
+    public void testConstructorDependencyInjection() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(ConstructorConfig.class);
+        Student student = context.getBean(Student.class);
+        assertEquals(1, student.getId());
+        assertEquals("John", student.getName());
+        assertEquals(1, student.getCollege().getId());
+        assertEquals("New York", student.getCollege().getName());
+    }
+}

spring-core/src/test/java/com/baeldung/configuration/SetterConfigTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.configuration;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import com.baeldung.model.Student;
+
+public class SetterConfigTest {
+    
+    @Test
+    public void testConstructorDependencyInjection() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(SetterConfig.class);
+        Student student = context.getBean(Student.class);
+        assertEquals(2, student.getId());
+        assertEquals("Tom", student.getName());
+        assertEquals(2, student.getCollege().getId());
+        assertEquals("Pittsburgh", student.getCollege().getName());
+    }
+}