Java 数据访问对象模式

Java设计模式 - 数据访问对象模式

数据访问对象模式或DAO模式将数据访问API与高级业务服务分离。

DAO模式通常具有以下接口和类。

• 数据访问对象接口定义模型对象的标准操作。

• 数据访问对象类实现以上接口。可能有多个实现，例如，一个用于数据库，一个用于文件。

• 模型对象简单的POJO包含get/set方法来存储数据。

例子

import java.util.ArrayList;
import java.util.List;class Employee {private String name;private int id;Employee(String name, int id) {this.name = name;this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getId() {return id;}public void setId(int id) {this.id = id;}
}interface EmployeeDao {public List<Employee> getAll();public Employee get(int id);public void updateStudent(Employee student);public void delete(Employee student);
}class EmployeeDaoImpl implements EmployeeDao {List<Employee> employeeList;public EmployeeDaoImpl() {employeeList = new ArrayList<Employee>();Employee emp1 = new Employee("Jack", 0);Employee emp2 = new Employee("Tom", 1);employeeList.add(emp1);employeeList.add(emp2);}@Overridepublic void delete(Employee student) {employeeList.remove(student.getId());System.out.println("Employee: No " + student.getId()+ ", deleted from database");}@Overridepublic List<Employee> getAll() {return employeeList;}@Overridepublic Employee get(int rollNo) {return employeeList.get(rollNo);}@Overridepublic void updateStudent(Employee emp) {employeeList.get(emp.getId()).setName(emp.getName());System.out.println("Emp:No " + emp.getId()+ ", updated in the database");}
}public class Main {public static void main(String[] args) {EmployeeDao empDao = new EmployeeDaoImpl();for (Employee emp : empDao.getAll()) {System.out.println("Emp: [No : " + emp.getId() + ", Name : "+ emp.getName() + " ]");}Employee emp = empDao.getAll().get(0);emp.setName("Jane");empDao.updateStudent(emp);empDao.get(0);System.out.println("Emp: [No : " + emp.getId() + ", Name : "+ emp.getName() + " ]");}
}

上面的代码生成以下结果。