Hibernate映射的超类关系和覆盖 [英] Hibernate Mapped Superclass relationships and overriding

问题描述

我有一个抽象的MappedSuperClass参与者，它由三种'参与者'扩展。然后每个人都使用自己的'项目'，也是一个抽象的MappedSuperClass。但是，我希望基类知道项目，以便我可以编写通用代码来与参与者交互。我如何使用Hibernate注释来指定它？以及如何在ExtendedParticipant和ExtendedProject类中覆盖它？

每个参与者类型和每个项目类型都有其自己的数据库表，其中包含现有的数据和ID（不是唯一的我不能改变。

下面的代码给了我IDE错误多对一的属性不应该是'映射超类'。 b
$ b

  @MappedSuperclass 
公共抽象类Participant实现了Persistable {
 
 ... 
 
 @ManyToOne 
 @JoinColumn（name =project_id）
 public Project getProject（）{
 return project; 
} 
 
 public void setProject（Project project）{
 this.project = project; 
} 
 
 ... 
} 
  

并且Project类与相同的问题大致相同：

  @MappedSuperclass 
 public abstract class Project implements Persistable { 
 
 ... 
 
 @OneToMany 
公共列表< Participant> getParticipants（）{
返回参与者; 
} 
 
 public void setProject（List< Participant> participants）{
 this.participants = participants; 
} 
 
 ... 
} 
  

解决方案

映射超类不是实体，它不能是关联的一部分。因此，将您的类映射为实体，并在其之上引入一个映射超类，或者使用 TABLE_PER_CLASS 策略。 另见

• EclipseLink：对MappedSuperclass的查询失败


• Hibernate - 持久化多态连接

I have an abstract MappedSuperClass, Participant, which is extended by three kinds of 'Participant'. Each one then uses its own kind of 'Project', also an abstract MappedSuperClass. However, I want the base class to know about Projects so I can write generic code to interact with Participants. How do I specify this using Hibernate annotations? and how will I override it in the ExtendedParticipant and ExtendedProject classes?

Each Participant type, and each Project type, have their own database tables with existing data and ids (not unique across tables) that I cannot change.

The following code gives me the IDE error "Many to one attribute should not be 'Mapped Superclass'".

@MappedSuperclass
public abstract class Participant implements Persistable {

    ...

    @ManyToOne
    @JoinColumn(name = "project_id")
    public Project getProject() {
        return project;
    }

    public void setProject(Project project) {
        this.project = project;
    }

    ...
}

and the Project class is much the same with the same problem:

@MappedSuperclass
public abstract class Project implements Persistable {

    ...

    @OneToMany
    public List<Participant> getParticipants() {
        return participants;
    }

    public void setProject(List<Participant> participants) {
        this.participants = participants;
    }

    ...
}

解决方案

A mapped superclass is not an Entity, it can't be part of an association. So map your classes as entities and either introduce a mapped superclass "above" them or use a TABLE_PER_CLASS strategy.

See also

• EclipseLink: Query to MappedSuperclass fails
• Hibernate - Persisting polymorphic joins

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