数据访问对象模式(Data Access Object Pattern)或 DAO 模式用于把低级的数据访问 API 或操作从高级的业务服务中分离出来。以下是数据访问对象模式的参与者
数据访问对象接口(Data Access Object Interface) - 该接口定义了在一个模型对象上要执行的标准操作。
数据访问对象实体类(Data Access Object concrete class) - 该类实现了上述的接口。该类负责从数据源获取数据,数据源可以是数据库,也可以是 xml,或者是其他的存储机制。
模型对象/数值对象(Model Object/Value Object) - 该对象是简单的 POJO,包含了 get/set 方法来存储通过使用 DAO 类检索到的数据。
代码:
1.数值对象
//数值对象
public class Student {
private String name;
private int rollNo;
public Student() {
super();
}
public Student(String name, int rollNo) {
super();
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;
}
@Override
public String toString() {
return "Student [name=" + name + ", rollNo=" + rollNo + "]";
}
}
2.数据访问对象接口
//数据访问对象接口
public interface StudentDao {
public List<Student> getAllStudents();
public Student getStudent(int rollNo);
public void updateStudent(Student student);
public void deleteStudent(Student student);
}
实现类
public class StudentDaoImpl implements StudentDao{
//数据集
private List<Student> students;
public StudentDaoImpl(List<Student> students) {
super();
this.students = students;
}
public StudentDaoImpl() {
super();
students=new ArrayList<Student>();
Student student1=new Student("zhangsan",1);
Student student2=new Student("lisi",2);
students.add(student1);
students.add(student2);
}
@Override
public List<Student> getAllStudents() {
return students;
}
@Override
public Student getStudent(int rollNo) {
return students.get(rollNo);
}
@Override
public void updateStudent(Student student) {
//模拟
students.get(student.getRollNo()).setName(student.getName());
System.out.println("数据更新");
}
@Override
public void deleteStudent(Student student) {
students.remove(student.getRollNo());
System.out.println("数据删除");
}
}
3.测试
public class Test {
public static void main(String[] args) {
StudentDao studentDao=new StudentDaoImpl();
List<Student> list=studentDao.getAllStudents();
//显示所有学生
for (Student student : list) {
System.out.println(student.toString());
}
System.out.println("---------------------");
//更新所有学生
Student student=studentDao.getStudent(0);
student.setName("Tom");
studentDao.updateStudent(student);
System.out.println("---------------------");
//获取学生
student=studentDao.getStudent(0);
System.out.println(student.toString());
}
}
4.测试结果
Student [name=zhangsan, rollNo=1]
Student [name=lisi, rollNo=2]
---------------------
数据更新
---------------------
Student [name=Tom, rollNo=1]
5.结论
一个POJO,一个接口,编程。
转载于
http://www.runoob.com/design-pattern/data-access-object-pattern.html