ManyToOne (Java EE 5)

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javax.persistence Annotation Type ManyToOne

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

Implements: Annotation
@Target(value={METHOD, FIELD})
@Retention(value=RUNTIME)

此注释定义对另一个带有多对一多样性的实体类的单值关联。一般不必显式指定目标实体，因为通常可以根据引用的对象类型推断出来。 
示例：

     @ManyToOne(optional=false) 
     @JoinColumn(name="CUST_ID", nullable=false, updatable=false)
     public Customer getCustomer() { return customer; }
since
en
Java Persistence 1.0
英文文档：

This annotation defines a single-valued association to another entity class that has many-to-one multiplicity. It is not normally necessary to specify the target entity explicitly since it can usually be inferred from the type of the object being referenced. 

     Example:

     @ManyToOne(optional=false) 
     @JoinColumn(name="CUST_ID", nullable=false, updatable=false)
     public Customer getCustomer() { return customer; }

Since:
Java Persistence 1.0

Optional Element Summary
 CascadeType[] cascade
          (Optional) The operations that must be cascaded to the target of the association.
 FetchType fetch
          (Optional) Whether the association should be lazily loaded or must be eagerly fetched.
 boolean optional
          (Optional) Whether the association is optional.
 Class targetEntity
          (Optional) The entity class that is the target of the association.
 

abstract public Class<T> targetEntity()
（可选）作为关联目标的实体类。

默认为存储关联的字段或属性的类型。

英文文档：

targetEntity

public abstract Class targetEntity
(Optional) The entity class that is the target of the association.

Defaults to the type of the field or property that stores the association.

Default:
void.class

abstract public CascadeType[] cascade()
（可选）必须串联到关联目标的操作。

默认情况下，不串联任何操作。

英文文档：

cascade

public abstract CascadeType[] cascade
(Optional) The operations that must be cascaded to the target of the association.

By default no operations are cascaded.

Default:
{}

abstract public FetchType fetch()
（可选）关联应该延迟加载还是必须立即获取。EAGER 战略是必须立即获取关联实体的持久性提供者运行时的要求。LAZY 战略是持久性提供者运行时的提示。
英文文档：

fetch

public abstract FetchType fetch
(Optional) Whether the association should be lazily loaded or must be eagerly fetched. The EAGER strategy is a requirement on the persistence provider runtime that the associated entity must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime.

Default:
EAGER

abstract public boolean optional()
（可选）关联是否是可选的。如果设置为 false，则必须总是存在非 null 关系。
英文文档：

optional

public abstract boolean optional
(Optional) Whether the association is optional. If set to false then a non-null relationship must always exist.

Default:
true
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一看就知道只有菜鸟才干这么无知的事啦。

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