springboot抽奖系统

可以使用Spring Boot来开发一个简单的抽奖系统。以下是一个简单的实现方法：

1. 定义奖品实体类，包括奖品名称、奖品数量、中奖概率等属性。
2. 定义用户实体类，包括用户ID、用户名、中奖状态等属性。
3. 使用Spring Data JPA来管理奖品和用户的数据。
4. 编写抽奖接口，调用随机数生成器来随机抽取奖品。
5. 添加异常处理和错误页面。

具体实现步骤如下：

1. 定义奖品实体类

@Entity
public class Prize {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    
    private String name;
    
    private Integer quantity;
    
    private Double probability;
    
    // getters and setters
}

2. 定义用户实体类

@Entity
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    
    private String name;
    
    private Boolean isWinner;
    
    // getters and setters
}

3. 使用Spring Data JPA来管理奖品和用户的数据

public interface PrizeRepository extends JpaRepository<Prize, Long> {
    
    List<Prize> findByQuantityGreaterThan(Integer quantity);
    
}

public interface UserRepository extends JpaRepository<User, Long> {
    
    List<User> findByIsWinner(Boolean isWinner);
    
}

4. 编写抽奖接口

@RestController
public class LotteryController {
    
    @Autowired
    private PrizeRepository prizeRepository;
    
    @Autowired
    private UserRepository userRepository;
    
    @GetMapping("/lottery")
    public String lottery() {
        List<Prize> prizes = prizeRepository.findByQuantityGreaterThan(0);
        if (prizes.isEmpty()) {
            return "Sorry, all the prizes have been drawn!";
        }
        
        Random random = new Random();
        Double luckyNumber = random.nextDouble();
        Double cumulativeProbability = 0.0;
        Prize prize = null;
        
        for (Prize p : prizes) {
            cumulativeProbability += p.getProbability();
            if (luckyNumber < cumulativeProbability) {
                prize = p;
                break;
            }
        }
        
        if (prize == null) {
            return "Sorry, you didn't win any prize this time!";
        }
        
        prize.setQuantity(prize.getQuantity() - 1);
        prizeRepository.save(prize);
        
        User user = new User();
        user.setName("Test User");
        user.setIsWinner(true);
        userRepository.save(user);
        
        return "Congratulations! You won a " + prize.getName() + "!";
    }
    
}

5. 添加异常处理和错误页面

@ControllerAdvice
public class ExceptionController {
    
    @ExceptionHandler(Exception.class)
    public String handleException(Exception e, Model model) {
        model.addAttribute("message", e.getMessage());
        return "error";
    }
    
}

@Controller
public class ErrorController implements org.springframework.boot.web.servlet.error.ErrorController {
    
    @GetMapping("/error")
    public String handleError(HttpServletRequest request, Model model) {
        Object status = request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
        if (status != null) {
            Integer statusCode = Integer.valueOf(status.toString());
            if (statusCode == HttpStatus.NOT_FOUND.value()) {
                model.addAttribute("message", "Sorry, the page you requested was not found!");
            } else if (statusCode == HttpStatus.INTERNAL_SERVER_ERROR.value()) {
                model.addAttribute("message", "Sorry, something went wrong on the server!");
            }
        }
        return "error";
    }
    
    @Override
    public String getErrorPath() {
        return "/error";
    }
    
}

以上是一个简单的Spring Boot抽奖系统的实现方法。当用户访问抽奖接口时，系统将随机抽取一个奖品并将其数量减1，同时创建一个中奖用户记录。如果所有奖品都已经被抽完，系统将返回相应的错误信息。如果出现其他异常，系统将返回错误页面并显示相应的错误信息。