DAO Class in Java

Data Access Object patterns, often known as DAO patterns, are used to divide high level business services from low level data accessing APIs or actions. The members of the Data Access Object Pattern are listed below.

Data Access Object Interface: The Data Access Object Interface specifies the common operations to be carried out on a model object (s).

Concrete Data Access Object class: This class implements the aforementioned interface. This class is in charge of obtaining data from a data source, which could be a database, XML, or another type of storage system.

Model or Value Object: This object is a straightforward POJO with get/set methods for storing data obtained using the DAO class.

Implementation

A student object will be created and used as a model as well as a value object.

Data Access Object Interface is called StudentDao.

The concrete class StudentDaoImpl implements the Data Access Object Interface. StudentDao will be used by DaoPatternDemo, our demo class, to show how to use the Data Access Object pattern.

Step 1:

Value Object creation.

S.java

public class S {
   private String n;
   private int r;

   S(String n, int r){
      this.n = n;
      this.r = r;
   }

   public String getName() {
      return n;
   }

   public void setName(String n) {
      this.n = n;
   }

   public int getRollNo() {
      return r;
   }

   public void setRollNo(int r) {
      this.r = r;
   }
}

Step 2:

Data Access Object Interface creation.

SD.java

import java.util.List;
public interface SD {
   public List<S> getAllStudents();
   public S getStudent(int r);
   public void updateStudent(S s);
   public void deleteStudent(S s);
}

Step 3:

Construct a class that implements the aforementioned interface.

SDI.java

import java.util.ArrayList;
import java.util.List;
public class SDI implements SD {
   // list is working as the database
   List<S> ss;
   public SDI(){
      ss = new ArrayList<S>();
      S s1 = new S("Sonoo",0);
      S s2 = new S("Jaiswal",1);
      ss.add(s1);
      ss.add(s2);		
   }
   @Override
   public void deleteStudent(S s) {
      students.remove(s.getRollNo());
      System.out.println(" Student: Roll No " + student.getRollNo() + ", has been deleted from the database");
   }
   // traversing list of students from the database
   @Override
   public List<S> getAllStudents() {
      return ss;
   }
   @Override
   public S getStudent(int r) {
      return ss.get(r);
   }
   @Override
   public void updateStudent(S s) {
      ss.get(s.getRollNo()).setName(s.getName());
      System.out.println(" Student: Roll No " + student.getRollNo() + ", has been updated in the database");
   }
}

Step 4:

Utilize the StudentDao to illustrate how to use the Data Access Object pattern.

DPDemo.java

public class DPDemo {
   public static void main(String[] args) {
      SD sD = new SDI();
      // print all the students
      for (S s : sD.getAllStudents()) {
         System.out.println("Student: [RollNo : " + s.getRollNo() + ", Name : " + s.getName() + " ]");
      }
      // update student
      S s =sD.getAllStudents().get(0);
      s.setName("JavaTpoint");
      sD.updateStudent(s);
      //get the student
      sD.getStudent(0);
      System.out.println("Student: [RollNo : " + s.getRollNo() + ", Name : " + s.getName() + " ]");		
   }
}

Step 5:

Check the results.