"Design mode" Data Access object mode

The data Access object pattern, or the DAO pattern, is used to separate low-level data access APIs or operations from advanced business services. The following are participants in the data Access object pattern.

• data Access Object Interface (Interface) -this interface defines the standard operations to be performed on a model object.
• The data Access Object entity class (concrete Class) -This class implements the interface described above. This class is responsible for getting data from a data source, which can be a database, or XML, or other storage mechanism.
• model Object/value Object/Numeric Object -The object is a simple POJO that contains the Get/set method to store the data retrieved by using the DAO class.

Realize

We will create a Student object as a model object or a numeric object. Studentdao is the data Access object interface. Studentdaoimpl is an entity class that implements the interface of a data access object. Daopatterndemo, our demo class uses Studentdao to demonstrate the use of the data Access object pattern.

Step 1

Creates a numeric object.

 Public classStudent {PrivateString name; Private intRollno; Student (String name,intRollno) {       This. Name =name;  This. Rollno =Rollno; }    PublicString GetName () {returnname; }    Public voidsetName (String name) { This. Name =name; }    Public intGetrollno () {returnRollno; }    Public voidSetrollno (intRollno) {       This. Rollno =Rollno; }}

Step 2

Creates a data Access object interface.

Import java.util.List;  Public Interface Studentdao {   public list<student> getallstudents ();      Public Student getstudent (int  rollno);     Public void updatestudent (Student Student);     Public void deletestudent (Student Student);}

Step 3

Create an entity class that implements the above interfaces.

Importjava.util.ArrayList;Importjava.util.List; Public classStudentdaoimplImplementsStudentdao {//list is treated as a databaseList<student>students;  PublicStudentdaoimpl () {Students=NewArraylist<student>(); Student Student1=NewStudent ("Robert", 0); Student Student2=NewStudent ("John", 1);      Students.add (STUDENT1);           Students.add (Student2); } @Override Public voiddeletestudent (Student Student) {students.remove (Student.getrollno ()); System.out.println ("Student:roll No" +Student.getrollno ()+ ", deleted from database"); }   //Retrieving student lists from the database@Override PublicList<student>getallstudents () {returnstudents; } @Override PublicStudent Getstudent (intRollno) {      returnStudents.get (Rollno); } @Override Public voidupdatestudent (Student Student) {students.get (Student.getrollno ()). SetName (Student.getname ()); System.out.println ("Student:roll No" +Student.getrollno ()+ ", updated in the database"); }}

Step 4

Use Studentdao to demonstrate the use of the data Access object pattern.

 Public classDaopatterndemo { Public Static voidMain (string[] args) {Studentdao Studentdao=NewStudentdaoimpl (); //output of all students       for(Student student:studentDao.getAllStudents ()) {System.out.println ("Student: [Rollno:" +student.getrollno () + ", Name:" +student.getname () + "]"); }      //Update StudentStudent Student =studentdao.getallstudents (). Get (0); Student.setname ("Michael");      Studentdao.updatestudent (student); //Get StudentsStudentdao.getstudent (0); System.out.println ("Student: [Rollno:" +student.getrollno () + ", Name:" +student.getname () + "]"); }}

Step 5

Verify the output.

Student: [rollno:0100, Name:michael]

"Design mode" Data Access object mode