JoinColumn (Java EE 5 SDK)

javax.persistence Annotation Type JoinColumn

@Target(value={METHOD,FIELD})
@Retention(value=RUNTIME)
public @interface JoinColumn

Is used to specify a mapped column for joining an entity association.

   Example:

   @ManyToOne
   @JoinColumn(name="ADDR_ID")
   public Address getAddress() { return address; }
 

从以下版本开始:

Java Persistence 1.0

name

public abstract String name

(Optional) The name of the foreign key column. The table in which it is found depends upon the context. If the join is for a OneToOne or Many- ToOne mapping, the foreign key column is in the table of the source entity. If the join is for a ManyToMany, the foreign key is in a join table. Default (only applies if a single join column is used): The concatenation of the following: the name of the referencing relationship property or field of the referencing entity; "_"; the name of the referenced primary key column. If there is no such referencing relationship property or field in the entity, the join column name is formed as the concatenation of the following: the name of the entity; "_"; the name of the referenced primary key column.

默认值:

""

referencedColumnName

public abstract String referencedColumnName

(Optional) The name of the column referenced by this foreign key column. When used with relationship mappings, the referenced column is in the table of the target entity. When used inside a JoinTable annotation, the referenced key column is in the entity table of the owning entity, or inverse entity if the join is part of the inverse join definition. Default (only applies if single join column is being used): The same name as the primary key column of the referenced table.

默认值:

""

unique

public abstract boolean unique

(Optional) Whether the property is a unique key. This is a shortcut for the UniqueConstraint annotation at the table level and is useful for when the unique key constraint is only a single field. It is not necessary to explicitly specify this for a join column that corresponds to a primary key that is part of a foreign key.

默认值:

false

nullable

public abstract boolean nullable

(Optional) Whether the foreign key column is nullable.

默认值:

true

insertable

public abstract boolean insertable

(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.

默认值:

true

updatable

public abstract boolean updatable

(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.

默认值:

true

columnDefinition

public abstract String columnDefinition

(Optional) The SQL fragment that is used when generating the DDL for the column.

Defaults to the generated SQL for the column.

默认值:

""

table

public abstract String table

(Optional) The name of the table that contains the column. If a table is not specified, the column is assumed to be in the primary table of the applicable entity.

默认值:

""

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