MVC pattern

MVC pattern stands for Model-View-Controller (Model-View-Controller) pattern. This pattern is used for layered development of applications.

• Model (Model) - A model represents an object or JAVA POJO that accesses data. It can also have logic to update the controller when the data changes.

• View - A view represents a visualization of the data contained by the model.

• Controller - Controllers act on models and views. It controls the flow of data to model objects and updates the view when the data changes. It separates the view from the model.

Implementation

We will create a Student object as a model. StudentView is a view class that outputs student detailed information to the console. StudentController is the controller class responsible for storing data into the Student object, and accordingly Update view StudentView.

MVCPatternDemo, our demo class uses StudentController to demonstrate the usage of the MVC pattern.

Step 1

Create the model.

Student.java

public class Student {
   private String rollNo;
   private String name;
   public String getRollNo() {
      return rollNo;
   }
   public void setRollNo(String rollNo) {
      this.rollNo = rollNo;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
}

Step 2

Create a view.

StudentView.java

public class StudentView {
   public void printStudentDetails(String studentName, String studentRollNo){
      System.out.println("Student: ");
      System.out.println("Name: " + studentName);
      System.out.println("Roll No: " + studentRollNo);
   }
}

Step 3

Create the controller.

StudentController.java

public class StudentController {
   private Student model;
   private StudentView view;

   public StudentController(Student model, StudentView view){
      this.model = model;
      this.view = view;
   }

   public void setStudentName(String name){
      model.setName(name);		
   }

   public String getStudentName(){
      return model.getName();		
   }

   public void setStudentRollNo(String rollNo){
      model.setRollNo(rollNo);		
   }

   public String getStudentRollNo(){
      return model.getRollNo();		
   }

   public void updateView(){				
      view.printStudentDetails(model.getName(), model.getRollNo());
   }	
}

Step 4

Use the StudentController method to demonstrate the use of the MVC design pattern.

MVCPatternDemo.java

public class MVCPatternDemo {
   public static void main(String[] args) {

      //从数据可获取学生记录
      Student model  = retriveStudentFromDatabase();

      //创建一个视图：把学生详细信息输出到控制台
      StudentView view = new StudentView();

      StudentController controller = new StudentController(model, view);

      controller.updateView();

      //更新模型数据
      controller.setStudentName("John");

      controller.updateView();
   }

   private static Student retriveStudentFromDatabase(){
      Student student = new Student();
      student.setName("Robert");
      student.setRollNo("10");
      return student;
   }
}

Step 5

Verify the output.

Student: 
Name: Robert
Roll No: 10
Student: 
Name: John
Roll No: 10