java学生选课系统代码

这里提供一个简单的Java学生选课系统后端代码示例，基于Spring Boot框架实现：

1. 学生类：

@Entity
@Table(name = "student")
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String password;

    // 省略getter和setter方法
}

2. 课程类：

@Entity
@Table(name = "course")
public class Course {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String teacher;

    // 省略getter和setter方法
}

3. 选课类：

@Entity
@Table(name = "selection")
public class Selection {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @ManyToOne
    @JoinColumn(name = "student_id")
    private Student student;
    @ManyToOne
    @JoinColumn(name = "course_id")
    private Course course;

    // 省略getter和setter方法
}

4. 学生服务类：

@Service
public class StudentService {
    @Autowired
    private StudentRepository studentRepository;

    public Student login(String name, String password) {
        return studentRepository.findByNameAndPassword(name, password);
    }

    public List<Course> getCourses(Long studentId) {
        return studentRepository.findById(studentId).get().getCourses();
    }

    public void selectCourse(Long studentId, Long courseId) {
        Student student = studentRepository.findById(studentId).get();
        Course course = courseRepository.findById(courseId).get();
        Selection selection = new Selection();
        selection.setStudent(student);
        selection.setCourse(course);
        selectionRepository.save(selection);
    }

    public void quitCourse(Long studentId, Long courseId) {
        Student student = studentRepository.findById(studentId).get();
        Course course = courseRepository.findById(courseId).get();
        Selection selection = selectionRepository.findByStudentAndCourse(student, course);
        if (selection != null) {
            selectionRepository.delete(selection);
        }
    }
}

5. 控制器类：

@RestController
@RequestMapping("/api/student")
public class StudentController {
    @Autowired
    private StudentService studentService;

    @PostMapping("/login")
    public Student login(@RequestParam String name, @RequestParam String password) {
        return studentService.login(name, password);
    }

    @GetMapping("/courses")
    public List<Course> getCourses(@RequestParam Long studentId) {
        return studentService.getCourses(studentId);
    }

    @PostMapping("/selectCourse")
    public void selectCourse(@RequestParam Long studentId, @RequestParam Long courseId) {
        studentService.selectCourse(studentId, courseId);
    }

    @PostMapping("/quitCourse")
    public void quitCourse(@RequestParam Long studentId, @RequestParam Long courseId) {
        studentService.quitCourse(studentId, courseId);
    }
}

以上代码仅为示例，具体实现需要根据实际需求进行调整和优化。