带有休眠注释的接口 [英] Interfaces with hibernate annotations

问题描述

我想知道如何注释界面

@Entity
@Table(name = "FOLDER_TABLE")
public class Folder implements Serializable, Hierarchy {

   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "folder_id", updatable = false, nullable = false)
   private int fId;

   @Column(name = "folder_name")
   private String folderName;

   @OneToMany(cascade = CascadeType.ALL)
   @JoinTable(name = "FOLDER_JOIN_FILE_INFORMATION_TABLE", joinColumns = 
{ @JoinColumn(name = "folder_id") }, inverseJoinColumns = 
{ @JoinColumn(name = "file_information_id") })
    private List< Hierarchy > fileInformation = new ArrayList< Hierarchy >();
}

上面和下面是2个类，它们实现了一个名为Hierarchy的接口，文件夹类有一个Hierarchyies列表，是一个文件夹或一个文件信息类

above and below are 2 classes that implement an interface called Hierarchy, the folder class has a list of Hierarchyies being a folder or a fileinformation class

@Entity
@Table(name = "FILE_INFORMATION_TABLE")
public class FileInformation implements Serializable, Hierarchy {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "file_information_id", updatable = false, nullable = false)
  private int ieId;
  @Column (name = "location")
  private String location;
}

我在网上搜索了一些注释或解决方法，但我无法映射简单的界面

I have searched the web for someway to annotate or a workaround but I cannot map the interface which is simply this

public interface Hierarchy {

}

我在带有文件夹的层次结构列表中遇到映射异常，但我不知道如何正确映射类.

I get a mapping exception on the List of hierarchies with a folder but I don't know how to map the class correctly.

推荐答案

您可以在 Hibernate 中映射接口，作为继承层次结构的一部分.这肯定可以通过 XML 映射实现，正如 Hibernate 参考资料的第 9 章，等等.

You can map interfaces in Hibernate, as part of inheritance hierarchies. This is quite surely possible with XML mapping, as it is described in Chapter 9 of the Hibernate reference, among others.

基于注释的映射是另一回事.我对它不太熟悉，但是 Java 持久化与 Hibernate 也包含了这方面的示例.适应你的情况，它看起来像

Annotation based mapping is a different story though. I am not so familiar with it, but Java Persistence with Hibernate includes examples for this too. Adapted to your case, it would look like

@MappedSuperclass
public interface Hierarchy {
}

@Entity
@Table(name = "FOLDER_TABLE")
public class Folder implements Serializable, Hierarchy { ... }

@Entity
@Table(name = "FILE_INFORMATION_TABLE")
public class FileInformation implements Serializable, Hierarchy { ... }

此映射将使用具有隐式多态性的每个具体类的表.

This mapping would use a table per concrete class with implicit polymorphism.

然而，其他来源表明接口的注解支持可能还没有工作/稳定:

However, other sources suggest that annotation support for interfaces may not be working / stable yet:

• 有一个关于使用 @Entity 的相关开放错误报告 带有接口的注释，其中还包含一些补丁，
• 这是一个相关(相当老的)线程，描述了一种解决方法使用 XML 映射.

• there is a related open bug report on using the @Entity annotation with interfaces, which also includes some patches,
• here is a related (fairly old) thread, describing a workaround using XML mapping.

所以你可能需要进行试验，包括改变你的继承映射策略，也许把接口变成一个抽象类(如果可能的话——因为一个类只能扩展一个基类)...

So you may need to experiment, including changing your inheritance mapping strategy, maybe turning the interface into an abstract class (if it's possible - since a class can only extend a single base class)...

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