86 lines
2.3 KiB
Dart
86 lines
2.3 KiB
Dart
/**
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数据访问对象模式（Data Access Object Pattern）
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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。
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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。
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模型对象/数值对象（Model Object/Value Object） - 简单数值对象，包含了 get/set 方法来存储通过使用 DAO 类检索到的数据。
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*/
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main(List<String> args) {
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StudentDao studentDao = new StudentDaoImpl();
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//输出所有的学生
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for (Student student in studentDao.getAllStudents()) {
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print("Student: [RollNo : ${student.rollNo}, Name : ${student.name} ]");
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}
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//更新学生
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Student student = studentDao.getAllStudents()[0];
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student.name = "Michael";
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studentDao.updateStudent(student);
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//获取学生
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studentDao.getStudent(0);
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print("Student: [RollNo : ${student.rollNo}, Name : ${student.name} ]");
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}
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//////////////////////////////////////////////////////////////////
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///
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/// 创建数值对象
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///
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class Student {
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int rollNo;
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String name;
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Student(this.name, this.rollNo);
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}
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///
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/// 创建数据访问对象接口
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///
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abstract class StudentDao {
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List<Student> getAllStudents();
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Student getStudent(int rollNo);
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void updateStudent(Student student);
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void deleteStudent(Student student);
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}
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///
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/// 创建实现了上述接口的实体类
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///
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class StudentDaoImpl implements StudentDao {
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//列表是当作一个数据库
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List<Student> _students;
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StudentDaoImpl() {
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_students = List<Student>();
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Student student1 = Student("Robert", 0);
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Student student2 = Student("John", 1);
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_students.add(student1);
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_students.add(student2);
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}
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@override
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void deleteStudent(Student student) {
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_students.remove(student.rollNo);
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print("Student: Roll No ${student.rollNo}, deleted from database");
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}
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//从数据库中检索学生名单
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@override
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List<Student> getAllStudents() {
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return _students;
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}
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@override
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Student getStudent(int rollNo) {
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return _students[rollNo];
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}
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@override
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void updateStudent(Student student) {
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_students[student.rollNo]?.name = student.name;
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print("Student: Roll No ${student.rollNo}, updated in the database");
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}
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}
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