增加Day5任务

doc/day5.md

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+本次实验的主要任务是完成期末案例的**业务逻辑层**（Service Layer）开发。业务逻辑层是连接图形界面（GUI）和数据访问层（DAO）的桥梁，它包含了所有的业务规则和流程控制。
+
+## 任务一：完成DAOFactory
+
+在开始service层开发之前，我们需要先完成`DAOFactory`类。这个类使用了单例模式和工厂模式，用于统一管理和获取DAO层的实例。
+
+```java
+package dao;
+
+import dao.impl.StudentDAOImpl;
+import dao.impl.TeacherDAOImpl;
+import dao.impl.LeaveRequestDAOImpl;
+
+/**
+ * DAO工厂类，用于获取各种DAO的实例
+ */
+public class DAOFactory {
+    private static final StudentDAO studentDAO = new StudentDAOImpl();
+    private static final TeacherDAO teacherDAO = new TeacherDAOImpl();
+    private static final LeaveRequestDAO leaveRequestDAO = new LeaveRequestDAOImpl();
+
+    /**
+     * 私有构造函数，防止实例化
+     */
+    private DAOFactory() {
+        // 私有构造函数，阻止实例化
+    }
+
+    /**
+     * 获取StudentDAO实例
+     * @return StudentDAO实例
+     */
+    public static StudentDAO getStudentDAO() {
+        return studentDAO;
+    }
+
+    /**
+     * 获取TeacherDAO实例
+     * @return TeacherDAO实例
+     */
+    public static TeacherDAO getTeacherDAO() {
+        return teacherDAO;
+    }
+
+    /**
+     * 获取LeaveRequestDAO实例
+     * @return LeaveRequestDAO实例
+     */
+    public static LeaveRequestDAO getLeaveRequestDAO() {
+        return leaveRequestDAO;
+    }
+}
+```
+
+`DAOFactory`类的主要特点：
+1. 使用私有构造函数防止外部实例化
+2. 使用静态字段保存DAO实例，确保全局唯一
+3. 提供静态方法获取DAO实例
+
+后期你可以这样使用它来获取DAO实例：
+
+```java
+// 获取StudentDAO实例
+StudentDAO studentDAO = DAOFactory.getStudentDAO();
+
+// 获取TeacherDAO实例
+TeacherDAO teacherDAO = DAOFactory.getTeacherDAO();
+
+// 获取LeaveRequestDAO实例
+LeaveRequestDAO leaveRequestDAO = DAOFactory.getLeaveRequestDAO();
+```
+
+## 任务二：开发Service层类
+
+在`src/service`目录下创建以下服务类：
+
+### 2.1 学生服务类（StudentService.java）
+
+```java
+package service;
+
+import dao.DAOFactory;
+import dao.StudentDAO;
+import model.Student;
+
+/**
+ * 学生信息服务类
+ */
+public class StudentService {
+    private final StudentDAO studentDAO = DAOFactory.getStudentDAO();
+
+    /**
+     * 根据ID查询学生
+     * @param id 学生ID
+     * @return 学生信息
+     */
+    public Student getStudentById(int id) {
+        return studentDAO.findById(id);
+    }
+
+    /**
+     * 学生登录
+     * @param studentId 学号
+     * @param password 密码
+     * @return 登录成功返回学生信息，失败返回null
+     */
+    public Student login(String studentId, String password) {
+        Student student = studentDAO.findByStudentId(studentId);
+        if (student != null && password.equals(student.getPassword())) {
+            return student;
+        }
+        return null;
+    }
+}
+```
+
+### 2.2 教师服务类（TeacherService.java）
+
+```java
+package service;
+
+import dao.DAOFactory;
+import dao.TeacherDAO;
+import model.Teacher;
+
+/**
+ * 教师信息服务类
+ */
+public class TeacherService {
+    private final TeacherDAO teacherDAO = DAOFactory.getTeacherDAO();
+
+    /**
+     * 教师登录
+     * @param teacherId 教师工号
+     * @param password 密码
+     * @return 登录成功返回教师信息，失败返回null
+     */
+    public Teacher login(String teacherId, String password) {
+        Teacher teacher = teacherDAO.findByTeacherId(teacherId);
+        if (teacher != null && password.equals(teacher.getPassword())) {
+            return teacher;
+        }
+        return null;
+    }
+}
+```
+
+### 2.3 请假服务类（LeaveRequestService.java）
+
+[LeaveRequestService.java](https://static.seahi.me/2024/12/LeaveRequestService.java)
+
+## 任务三：创建Service工厂类
+
+为了方便获取Service实例，创建一个ServiceFactory类：
+
+```java
+package service;
+
+/**
+ * Service工厂类，用于获取各种Service的实例
+ */
+public class ServiceFactory {
+    private static final StudentService studentService = new StudentService();
+    private static final TeacherService teacherService = new TeacherService();
+    private static final LeaveRequestService leaveRequestService = new LeaveRequestService();
+
+    private ServiceFactory() {
+        // 私有构造函数，防止实例化
+    }
+
+    public static StudentService getStudentService() {
+        return studentService;
+    }
+
+    public static TeacherService getTeacherService() {
+        return teacherService;
+    }
+
+    public static LeaveRequestService getLeaveRequestService() {
+        return leaveRequestService;
+    }
+}
+```
+
+## 任务四：单元测试
+
+在`test/service`目录下创建对应的测试类：
+
+1. [StudentServiceTest.java](https://static.seahi.me/2024/12/StudentServiceTest.java) - 测试学生登录功能
+2. [TeacherServiceTest.java](https://static.seahi.me/2024/12/TeacherServiceTest.java) - 测试教师登录功能
+3. [LeaveRequestServiceTest.java](https://static.seahi.me/2024/12/LeaveRequestServiceTest.java) - 测试请假申请和审批功能
+