java JPA - @OneToMany 作为地图
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JPA - @OneToMany as a Map
提问by dnc253
This seems like a common enough case, but as JPA newbie, I am having trouble figuring this out. I'm using EclipseLink and PostgreSQL, but this should relate to just the JPA spec.
这似乎是一个足够常见的案例，但作为 JPA 新手，我无法弄清楚这一点。我正在使用 EclipseLink 和 PostgreSQL，但这应该只与 JPA 规范有关。
I have one table PRIMARYthat has an ID and then a bunch of other columns. There is another table SECONDARYthat has a foreign key into the PRIMARYtable also called ID. This SECONDARYtable has a composite key of that IDand a varchar representing a locale.
我有一个表PRIMARY，它有一个 ID，然后是一堆其他列。还有另一个表SECONDARY，该PRIMARY表有一个外键，也称为ID. 这个SECONDARY表有一个组合键ID和一个表示语言环境的 varchar。
So, in the Primaryentity I want to have a field of type Map<String, Secondary>where the key is the locale string from the SECONDARYtable and the entry is the Secondaryentity. My Secondaryclass looks like this:
因此，在Primary实体中，我想要一个类型的字段，Map<String, Secondary>其中键是SECONDARY表中的区域设置字符串，条目是Secondary实体。我的Secondary课是这样的：
@Entity
public class Secondary
{
@Id
private Long id;
@Id
private String locale;
private String str1;
private String str2;
.....
}
I'm thinking I want to use the @MapKeyJoinColumnannotation, but I can't seem to get the other annotations to work. I tried this:
我想我想使用@MapKeyJoinColumn注释，但我似乎无法让其他注释起作用。我试过这个：
@OneToMany
@JoinColumn(name="ID")
@MapKeyJoinColumn(name="LOCALE")
private Map<String, Secondary> secondaryByLocale;
This resulted in it trying to select a column named secondaryByLocale_key which doesn't exist.
这导致它尝试选择一个不存在的名为 secondaryByLocale_key 的列。
I then tried this:
然后我尝试了这个：
@OneToMany
@JoinTable(name="SECONDARY",
joinColumns={@JoinColumn(name="ID")},
inverseJoinColumns=@JoinColumn(name="ID"))
@MapKeyJoinColumn(name="LOCALE")
private Map<String, Secondary> secondaryByLocale;
This results in the following error:
这会导致以下错误：
Exception Description: The @JoinColumns on the annotated element [field secondaryByLocale] from the entity class [class com.foo.Primary] is incomplete. When the source entity class uses a composite primary key, a @JoinColumn must be specified for each join column using the @JoinColumns. Both the name and the referencedColumnName elements must be specified in each such @JoinColumn.
I tried adding the referencedColumnName to the annotation (I wasn't sure what it even should be), but I got the same error.
我尝试将 referencedColumnName 添加到注释中（我什至不确定它应该是什么），但我遇到了同样的错误。
As suggested, I tried using @MapKeyas follows:
按照建议，我尝试使用@MapKey如下：
@OneToMany
@JoinColumn(name="ID")
@MapKey(name="LOCALE")
private Map<String, Secondary> secondaryByLocale;
This results in the following error:
这会导致以下错误：
Exception Description: The map key [LOCALE] on the entity class [class com.foo.Secondary] could not be found for the mapping [org.eclipse.persistence.mappings.UnidirectionalOneToManyMapping[secondaryByLocale]].
Maybe I'm going about this all wrong, and there's a better way to annotate the Map field. Any help would be much appreciated.
也许我对这一切都做错了，并且有一种更好的方法来注释 Map 字段。任何帮助将非常感激。
采纳答案by MattR
Try using @MapKey(name = "locale")instead.
尝试使用@MapKey(name = "locale")。
@MapKeyJoinColumnis used when your map key is an entity, but here you're just using the locale String.
@MapKeyJoinColumn当您的地图键是实体时使用，但在这里您只使用区域设置字符串。
回答by Kedar Birajdar
In my case, it is worked with @OneToMany(cascade=CascadeType.PERSIST) @MapKeyColumn(name="COLUMN_NAME")
就我而言，它与 @OneToMany(cascade=CascadeType.PERSIST) @MapKeyColumn(name="COLUMN_NAME") 一起使用
or
或者
You can directly try with only @OneToMany(cascade=CascadeType.PERSIST)
你可以直接尝试只用@OneToMany(cascade=CascadeType.PERSIST)
