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。
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数据访问对象接口定义模型对象的标准操作。
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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。
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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); } @Override public void delete(Employee student) { employeeList.remove(student.getId()); System.out.println("Employee: No " + student.getId() + ", deleted from database"); } @Override public List<Employee> getAll() { return employeeList; } @Override public Employee get(int rollNo) { return employeeList.get(rollNo); } @Override public 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。