休眠异常：缺少列（存在列） [英] Hibernate Exception: Missing Column (column exists)

问题描述

好的，在数据​​库中我们有一个名为distributionCompanies的表，如下所示：

  CREATE TABLE`distributionCompanies`（ 
`distributionCompanyID` INT（11）NOT NULL，
````````````` 
  

我试图用Hibernate将这张表映射到一个类：

  @Entity 
 @Table（name =distributionCompanies）
 public class DistributionCompany实现DatabaseObject {
 @Id 
 @GeneratedValue 
 @Column（name =distributionCompanyID，length = 11，unique = true，nullable = false）
 private int distributionCompanyID; 
 .... 
  

然而，在运行时，我遇到了这个问题：

 创建初始SessionFactory failedorg.hibernate.HibernateException：缺少database2.distributionCompanies中的列：distributionCompanyID_distributionCompanyID 
  

这不是数据库中唯一的表格，我已经设法使用相同的方法成功映射其他类，所以我有点难过至于为什么这是造成问题。

感谢您的时间，
塞缪尔史密斯

编辑：为了回应Xavi的评论，我暂时删除了该列的另一个映射，并且错误消失了，所以坏蛋可能在以下代码中：

  @ManyToOne（targetEntity = DistributionCompany.class）
 @JoinTable（name =distributionCompanies，joinColumns = {@JoinColumn（name =distributionCompanyID，nullable = false）}） 
 private int distributionCompanyID; 
  

解决方案

Hibernate正在寻找名为 distributionCompanyID_distributionCompanyID 放入您的 distributionCompanies 表中。

这可能是由于 ToOne 关联映射到此表而没有 @JoinColum 。

从 Hibernate文档：

@JoinColumn属性是可选的，默认值是一对一的，并置所有者方的关系名称，_（下划线）以及所有权方主键列的名称。在这个示例中，company_id是因为属性名称是company，并且company的列id是id。

如果您有 @ManyToOne 或 @OneToOne 在另一个实体中关联映射，这可以解释为什么Hibernate正在寻找这样一个列。

编辑看到您发布的关联映射，它看起来应该是：

  @ManyToOne（targetEntity = DistributionCompany.class）
 @JoinColumn（name =distributionCompanyID）
 private DistributionCompany distributionCompany; 
  

@JoinTable 注释用于指定一个连接表（这意味着一个用于模拟多对多关联的中间表）。而映射关联的要点是处理映射的对象实例（在本例中为 DistributionCompany ，而不仅仅是 distributionCompanyId ）。

Okay, so within the database we have a table called distributionCompanies, created like so:

CREATE TABLE `distributionCompanies` (
    `distributionCompanyID` INT(11) NOT NULL,
    `distributionCompanyName` VARCHAR(255) NOT NULL,
     PRIMARY KEY (distributionCompanyID)
);

I'm trying to map this table to a class using Hibernate:

@Entity
@Table(name = "distributionCompanies")
public class DistributionCompany implements DatabaseObject {
    @Id
    @GeneratedValue
    @Column(name = "distributionCompanyID", length = 11, unique = true, nullable = false)
    private int distributionCompanyID;
....

However, when running, I hit this issue:

Initial SessionFactory creation failedorg.hibernate.HibernateException: Missing column: distributionCompanyID_distributionCompanyID in database2.distributionCompanies

This isn't the only table in the database, and I've managed to map other classes successfully using the same method, so I'm a little stumped as to why this is causing an issue.

Thank you for your time, Samuel Smith

EDIT: In response to Xavi's comment, I temporarily removed another mapping for the column, and the error went away, so the bad-egg probably lays in the following code:

@ManyToOne(targetEntity = DistributionCompany.class)
@JoinTable(name = "distributionCompanies", joinColumns = { @JoinColumn(name =    "distributionCompanyID", nullable = false) })
private int distributionCompanyID;

解决方案

Hibernate is looking for a column named distributionCompanyID_distributionCompanyID in your distributionCompanies table.

This is probably due to a ToOne association mapping towards this table without @JoinColum.

From Hibernate Documentation:

The @JoinColumn attribute is optional, the default value(s) is like in one to one, the concatenation of the name of the relationship in the owner side, _ (underscore), and the name of the primary key column in the owned side. In this example company_id because the property name is company and the column id of Company is id.

If you've got a @ManyToOne or @OneToOne association mapping in another entity, this would explain why Hibernate is looking for such a column.

EDIT Seeing the association mapping you posted, it looks like it should be:

@ManyToOne(targetEntity = DistributionCompany.class)
@JoinColumn(name = "distributionCompanyID")
private DistributionCompany distributionCompany;

The @JoinTable annotation is used to specify a join table (that means an intermediate table used to model many-to-many associations). And the point of mapping an association would be to dispose of the mapped object instance (in this case a DistributionCompany, not just a distributionCompanyId).

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