Java如何开发一个简易的活动报名小程序

@Entity
public class Activity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String description;
    private LocalDateTime time;
    private String location;
    private Integer maxParticipants;
    private Integer currentParticipants = 0;

    // 构造方法、getter 和 setter 省略
}

@Entity
public class Participant {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String phone;
    
    @ManyToOne
    @JoinColumn(name = "activity_id")
    private Activity activity;

    // 构造方法、getter 和 setter 省略
}

public interface ActivityRepository extends JpaRepository {}

public interface ParticipantRepository extends JpaRepository {
    List findByActivityId(Long activityId);
}

@Controller
public class ActivityController {

    @Autowired
    private ActivityRepository activityRepo;

    @Autowired
    private ParticipantRepository participantRepo;

    // 展示所有活动
    @GetMapping("/")
    public String listActivities(Model model) {
        model.addAttribute("activities", activityRepo.findAll());
        return "index";
    }

    // 报名页面
    @GetMapping("/signup/{id}")
    public String showSignupForm(@PathVariable Long id, Model model) {
        Activity activity = activityRepo.findById(id).orElse(null);
        if (activity == null || activity.getCurrentParticipants() >= activity.getMaxParticipants()) {
            return "error";
        }
        model.addAttribute("activity", activity);
        model.addAttribute("participant", new Participant());
        return "signup";
    }

    // 提交报名
    @PostMapping("/signup/{id}")
    public String registerParticipant(@PathVariable Long id,
                                      @ModelAttribute Participant participant,
                                      Model model) {
        Activity activity = activityRepo.findById(id).orElse(null);
        if (activity == null || activity.getCurrentParticipants() >= activity.getMaxParticipants()) {
            model.addAttribute("message", "报名失败：活动已满或不存在");
            return "result";
        }

        participant.setActivity(activity);
        participantRepo.save(participant);

        activity.setCurrentParticipants(activity.getCurrentParticipants() + 1);
        activityRepo.save(activity);

        model.addAttribute("message", "报名成功！");
        return "result";
    }
}

  

  

  
时间: 
  
地点: 
  
人数: /
  报名

spring.datasource.url=jdbc:h2:mem:activitydb
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto=create-drop
spring.h2.console.enabled=true

@PostConstruct
public void init() {
    Activity act = new Activity();
    act.setName("Java技术分享会");
    act.setDescription("介绍Spring Boot实战技巧");
    act.setTime(LocalDateTime.now().plusDays(7));
    act.setLocation("科技大厦3楼会议室");
    act.setMaxParticipants(30);
    activityRepo.save(act);
}