用spring boot编写流量计 站点编号 水位保留2位小数， 流速保留2位小数 ，流量保留2位小数以及时间的代码

1. 编写实体类

@Entity
@Table(name = "flow_meter")
public class FlowMeter {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "site_no", nullable = false)
    private String siteNo;

    @Column(name = "water_level", nullable = false, precision = 2)
    private Double waterLevel;

    @Column(name = "flow_speed", nullable = false, precision = 2)
    private Double flowSpeed;

    @Column(name = "flow_rate", nullable = false, precision = 2)
    private Double flowRate;

    @Column(name = "time", nullable = false)
    private LocalDateTime time;

    // getter and setter
}

2. 编写Repository接口

public interface FlowMeterRepository extends JpaRepository<FlowMeter, Long> {
}

3. 编写Service类

@Service
public class FlowMeterService {

    private final FlowMeterRepository flowMeterRepository;

    public FlowMeterService(FlowMeterRepository flowMeterRepository) {
        this.flowMeterRepository = flowMeterRepository;
    }

    public FlowMeter save(FlowMeter flowMeter) {
        return flowMeterRepository.save(flowMeter);
    }

    public List<FlowMeter> findAll() {
        return flowMeterRepository.findAll();
    }

    public Optional<FlowMeter> findById(Long id) {
        return flowMeterRepository.findById(id);
    }

    public void deleteById(Long id) {
        flowMeterRepository.deleteById(id);
    }
}

4. 编写Controller类

@RestController
@RequestMapping("/flow-meter")
public class FlowMeterController {

    private final FlowMeterService flowMeterService;

    public FlowMeterController(FlowMeterService flowMeterService) {
        this.flowMeterService = flowMeterService;
    }

    @PostMapping
    public FlowMeter save(@RequestBody FlowMeter flowMeter) {
        return flowMeterService.save(flowMeter);
    }

    @GetMapping
    public List<FlowMeter> findAll() {
        return flowMeterService.findAll();
    }

    @GetMapping("/{id}")
    public Optional<FlowMeter> findById(@PathVariable Long id) {
        return flowMeterService.findById(id);
    }

    @DeleteMapping("/{id}")
    public void deleteById(@PathVariable Long id) {
        flowMeterService.deleteById(id);
    }
}

5. 配置数据库

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/flow_meter?useSSL=false&serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    database-platform: org.hibernate.dialect.MySQL8Dialect
    hibernate:
      ddl-auto: update
    show-sql: true

6. 运行程序

启动Spring Boot应用程序后，可使用Postman或其他工具测试API。例如，要保存流量计数据：

POST http://localhost:8080/flow-meter

{
    "siteNo": "001",
    "waterLevel": 1.23,
    "flowSpeed": 4.56,
    "flowRate": 7.89,
    "time": "2021-09-01T10:00:00"
}

要获取所有流量计数据：

GET http://localhost:8080/flow-meter

要获取特定ID的流量计数据：

GET http://localhost:8080/flow-meter/1

要删除特定ID的流量计数据：

DELETE http://localhost:8080/flow-meter/1