映射一个java.util.Map＆LT;实体，实体GT;在使用Hibernate JPA注解 [英] Mapping a java.util.map<entity, entity> in hibernate using JPA annotations

问题描述

我似乎，在Hibernate中，其中的关键和资源都是实体由Hibernate映射映射集合类的问题。

I seem to be having an issue with mapping a collection in hibernate where the key and the resource are both entities to be mapped by hibernate.

而从文档（我对这个问题的主要资源一直是这个，但我当然欢迎任何人：的 http://docs.jboss.org/hibernate/orm/3.6/reference/en-US/html/collections.html ）它会出现这应该是一个相对简单的任务，我似乎无法获得地图的关键要坚持。

Whereas from the documentation (my main resource for this issue has been this, but I of course welcome any others: http://docs.jboss.org/hibernate/orm/3.6/reference/en-US/html/collections.html) it would appear that this should be a relatively simple task, I just can't seem to get the key of the map to persist.

，因为它代表我的code是这样的：

My code as it stands looks like this:

父类：

@Entity
public class Parent {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @MapKey
    @MapKeyClass(Key.class)
    @ManyToMany(cascade = CascadeType.ALL)
    private Map<Key, Resource> map;

Key类：

@Table(name="ParentKey")
@Entity
public class Key implements Comparable<Key> {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @Column(name = "hierarchyKey")
    private int key;

的资源类是一个相对简单的POJO并持续正常，所以我认为这个问题是不是在这个类。

The resource class is a relatively simple POJO and persists fine, so I would assume that the issue is not in that class.

我也碰到过对Hibernate的论坛上的一些文件中的注释@MapKeyManyToMany，但我相信这之后一直去precated。

I did come across the annotation @MapKeyManyToMany in some documentation on the hibernate forums, but I believe this has since been deprecated.

该数据库的架构是不重要的在这个阶段，主要关注的只是确保一切持续到数据库中。我们正在使用MySQL的底层数据库。

The schema of the database is unimportant at this stage, the main concern is simply making sure everything persists to the database. We're using MySQL for the underlying database.

正如我敢肯定，你可能已经猜到，任何涉及词地图搜索，休眠，实体按键返回大量不相关的这个问题的问题，但我敢肯定，这必须是发生相当的情况常在映射的情况而言。

As I'm sure you can probably guess, any search involving the words map, hibernate, entity and key return a large amount of questions not related to this issue, though I'm sure this must be a situation that occurs quite often in terms of mapping situations.

我不经常提出的问题，但我是一个积极的读者，所以请让我知道，如果需要任何更多的信息。

I don't often submit questions, but I am an active reader, so please let me know if any more info is required.

推荐答案

按规定这工作。操作不级联到映射的键。它们级联只的值。在文档此被告知用下面的话：

This works as specified. Operations are not cascaded to the key of the map. They are cascaded only to the value. In documentation this is told with following words:

在目标集合是一个java.util.Map，级联元素
  适用于地图值

When the target collection is a java.util.Map, the cascade element applies to the map value.

重点必须单独保留。

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