Java 外键为空：Hibernate Spring

我尝试将对象运行保存到数据库。我定义了跑步和城市的关系。一个城市可能有很多次跑步。我对城市id有问题。为空

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
java.sql.SQLIntegrityConstraintViolationException: Column 'city_id' cannot be null

我的实体和控制员： 城市

控制器

@CrossOrigin
@RestController
@RequestMapping("/api/")
public class RunController {

    private RunRepository runRepository;
    private RunService runService;

    public RunController(RunRepository runRepository, RunService runService) {
        this.runRepository = runRepository;
        this.runService = runService;
    }

    @GetMapping("runs")
    public ResponseEntity<List<Run>> getRuns() {
        return runService.getRuns();
    }

    @PostMapping("runs")
    public ResponseEntity addRun(@RequestBody Run run) {

        return new ResponseEntity<>(runRepository.save(run), HttpStatus.OK);
    }
}

@交叉起源
@RestController
@请求映射（“/api/”）
公共类运行控制器{
私有运行库运行库；
私人运行服务；
公共RunController（RunRepository RunRepository、RunService RunService）{
this.runRepository=runRepository；
this.runService=runService；
}
@GetMapping（“运行”）
公共响应getRuns（）{
返回runService.getRuns（）；
}
@后映射（“运行”）
公共响应属性addRun（@RequestBody Run）{
返回新的响应属性（runRepository.save（run），HttpStatus.OK）；
}
}

我想在DB中保存运行。 我的测试请求如下所示：

{ “名称运行”：“测试”， “距离”：“5.0”， “日期”：“2020-12-12”， “我的时间”：“50:40”， “城市”：“测试1” }

Intelijj中评估表达式的结果：

---

为什么城市=空？映射中有错误吗

首先，请使用

Long

作为id。最好也添加

@Entity

注释

@Entity
public class City {

    @Id
    @GeneratedValue
    private Long id;

    @OneToMany(mappedBy = "city", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Run> runs = new ArrayList<>();

}

@Entity
public class Run {

    @Id
    @GeneratedValue
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    private City city;

}

显然，数据库中应该有一个id为

1L的城市

其他选择包括

使用类似于
session.load（）
Hibernate Simulation with Spring repository的方法创建
City
，而无需从Database加载
完全按id加载城市

实体

---

如果你想保存任何跑步课程

Run run = new Run();
City city = new City();
city.getRuns().add(run);
runRepository.save(run);

---

如果要保存任何run类，首先需要插入city类的to（Arraylist）runs变量，如city.getRuns（）.add（run）在填充run之后，您可以运行Repository.save（run）

我的样品也在这里。你可以看看我的课程

第一类被称为病人

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@ToString
@Table(name = "aapatient")
public class Patient {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "AA_PATIENT_SEQ")
    @SequenceGenerator(sequenceName = "AA_PATIENT_SEQ", allocationSize = 1, name = "AA_PATIENT_SEQ")
    @Column(name = "patientid")
    private Long patientid;
    private String name;
    private String lastname;  

    @OneToMany(mappedBy = "patient", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Problem> problems; 
}

---

您可以尝试使用此json，但需要在json中传递城市id

{
    "nameRun": "test",
    "distance": "5.0",
    "date": "2020-12-12",
    "myTime": "50:40",
    "city": {
        "id": 1,
        "name": "test1"
    }
}

---

谢谢

您使用什么数据库？请提供您的

城市

和

运行

表定义（ddl sql）。此请求无效。我得到的列“city\u id”不能为空

Run run = new Run();
City city = new City();
city.getRuns().add(run);
runRepository.save(run);

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@ToString
@Table(name = "aapatient")
public class Patient {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "AA_PATIENT_SEQ")
    @SequenceGenerator(sequenceName = "AA_PATIENT_SEQ", allocationSize = 1, name = "AA_PATIENT_SEQ")
    @Column(name = "patientid")
    private Long patientid;
    private String name;
    private String lastname;  

    @OneToMany(mappedBy = "patient", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Problem> problems; 
}

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
@Entity
@Table(name="aaproblem")
public class Problem{

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "AA_PATIENT_SEQ")
    @SequenceGenerator(sequenceName = "AA_PATIENT_SEQ", allocationSize = 1, name = "AA_PATIENT_SEQ")
    @Column(name = "problemid")
    private Long problemid;
    private String problemName;
    private String problemDetail; 

    @Temporal(TemporalType.TIMESTAMP)
    Date creationDate;

    @NotNull
    @ManyToOne(optional = true, fetch = FetchType.LAZY)
    @JoinColumn(name = "patient_id")
    private Patient patient;

}

{
    "nameRun": "test",
    "distance": "5.0",
    "date": "2020-12-12",
    "myTime": "50:40",
    "city": {
        "id": 1,
        "name": "test1"
    }
}