Java Data Access Object pattern

Mode data access object (Data Access Object Pattern) for the DAO mode or a low-level API or data access operations from advanced business services. The following is a participant data access object model.

Interface data access object (the Data Object Access Interface) - This defines a standard interface to operate on a model of the object to be executed.

Data Access Objects entity classes (the Data Object Access Concrete class) - This class implements the above interface. Class is responsible for data acquisition from the data source, data source can be a database, it can be xml, storage or other mechanisms.

Model object / target value (the Model Object / the Value Object) - the object is a simple POJO, containing get / set methods DAO classes to store data retrieved by using.

Student.java

public class Student { //创建数值对象

   private String name;
       private int rollNo;

       Student(String name, int rollNo){
          this.name = name;
          this.rollNo = rollNo;
       }

       public String getName() {
          return name;
       }

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

       public int getRollNo() {
          return rollNo;
       }

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

}

StudentDao.java

import java.util.List;

public interface StudentDao {// create a data access object interface

   public List <Student> getAllStudents ();
       public Student getStudent (int rollNo);
       public void updateStudent (Student Student);
       public void deleteStudent (Student Student);

}

StudentDaoImpl.java

import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements StudentDao {

   //列表是当作一个数据库
   List<Student> students;

   public StudentDaoImpl(){
      students = new ArrayList<Student>();
      Student student1 = new Student("Robert",0);
      Student student2 = new Student("John",1);
      students.add(student1);
      students.add(student2);
   }
   @Override
   public void deleteStudent(Student student) {
      students.remove(student.getRollNo());
      System.out.println("Student1: Roll No " + student.getRollNo()
         +", deleted from database");
   }

   //从数据库中检索学生名单
   @Override
   public List<Student> getAllStudents() {
      return students;
   }

   @Override
   public Student getStudent(int rollNo) {
      return students.get(rollNo);
   }

   @Override
   public void updateStudent(Student student) {
      students.get(student.getRollNo()).setName(student.getName());
      System.out.println("Student2: Roll No " + student.getRollNo()
         +", updated in the database");
   }
}

DaoPatternDemo.java

public class DaoPatternDemo {// StudentDAO used to demonstrate the usage of the data access object model

   public static void main (String [] args) {
       StudentDAO StudentDAO new new StudentDaoImpl = ();
       // output of all students
       for (Student student: studentDao.getAllStudents ( )) {
           System.out.println ( "Student3: [RollNo:"
                    + student.getRollNo () + ", the Name:" + student.getName () + "]");
       }

       // update the student
       student student = studentDao. . getAllStudents () gET (0);
       student.setName ( "Walker");
       studentDao.updateStudent (student);

       // get students
       studentDao.getStudent (0);
       System.out.println ( "Student4: [RollNo:"
                 +student.getRollNo()+", Name : "+student.getName()+" ]");
   }

}

Java Data Access Object pattern

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