具有一对多映射的 POST REST API：不能为空错误

Question

我有两张桌子：tbl_services & tbl_sub_services。一项服务可以有多个子服务。我正在使用 spring boot 开发 REST API 并尝试在服务和子服务表中发布数据。我可以在services 表中发布数据，但在sub-services 表中发布时遇到问题。这是one-to-Many 双向映射。

这是我在邮递员中遇到的一个例外。

{
"timestamp": "2019-06-09T04:10:22.002+0000",
"status": 500,
"error": "Internal Server Error",
"message": "could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement",
"trace": "org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement\n\tat 
.
.
.
.
'tbl_services_id' cannot be null\n\tat com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117)\n\tat com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)\n\tat com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)\n\tat com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:955)\n\tat com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1094)\n\tat com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1042)\n\tat com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1345)\n\tat com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1027)\n\tat com.zaxxer.hikari.pool.ProxyPreparedStatement.executeUpdate(ProxyPreparedStatement.java:61)\n\tat com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeUpdate(HikariProxyPreparedStatement.java)\n\tat org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)\n\t... 94 more\n",
"path": "/api/subservices"

这是两个表的结构：

实体类：
服务类

@Entity
@Table(name="tbl_services")
public class Service {

// define fields
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="tbl_services_id")
private int id;

@Column(name="service_name")
private String serviceName;

@Column(name="service_desc")
private String serviceDesc;

@Column(name="service_image")
private String serviceImage;

@OneToMany(mappedBy="service",
        cascade= {CascadeType.PERSIST, CascadeType.MERGE,
            CascadeType.DETACH, CascadeType.REFRESH})
private List<SubService> subServices;

public List<SubService> getSubServices() {
    return subServices;
}

public void setSubServices(List<SubService> subServices) {
    this.subServices = subServices;
}
}

SubService.class

@Entity
@Table(name="tbl_sub_services")
public class SubService {

// define fields
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="tbl_sub_services_id")
private int id;

@ManyToOne(
        cascade= {CascadeType.PERSIST, CascadeType.MERGE,
                CascadeType.DETACH, CascadeType.REFRESH})
@JoinColumn(name="tbl_services_id")
@JsonIgnore
private Service service;

public Service getService() {
    return service;
}

@Column(name="sub_service_name")
private String subServiceName;

@Column(name="sub_service_desc")
private String subServiceDesc;

@Column(name="sub_service_image")
private String subServiceImage;

我正在尝试从邮递员那里发布数据，然后出现异常。这是我从邮递员那里发布的数据。

这里是 SubServicesHibernateDAOImpl.class

@Override
public void saveSubService(SubService theSubService) {
    // get the current hibernate session
    Session currentSession = entityManager.unwrap(Session.class);
    System.out.println("SubService object : "+theSubService);       
    currentSession.saveOrUpdate(theSubService);
}  

编辑： 这是我在 saveSubService 方法中收到的 json 有效负载：

[id=0, service=null, subServiceName=GST, subServiceDesc=GST is a subservice which currently having , subServiceImage=path-to-image]

Answer 1

你得到：

无法执行语句； SQL [不适用]；约束 [null]

我看到您在请求中传递了service，但我没有看到您在保存SubService 之前加载它：

@Override
public void saveSubService(SubService theSubService) {
    Session currentSession = entityManager.unwrap(Session.class);
    Service loadedService = currentSession.load(Service.class
           , theSubService.getService.getId();

    theSubService.setService(loadedService);         

    currentSession.saveOrUpdate(theSubService);
}

或尝试简单地合并，因为您已经有了适当的级联：

@Override
public void saveSubService(SubService theSubService) {
    // get the current hibernate session
    Session currentSession = entityManager.unwrap(Session.class);
    System.out.println("SubService object : "+theSubService);       
    currentSession.merge(theSubService);
}

另外，我不确定您为什么需要unwrap 会话。 EntityManager 及其接口在这种情况下就足够了。