FetchType (Java EE 5 SDK)

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Java EE 5 SDK

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摘要: 嵌套 | ENUM 构造器 | 字段 | 方法

详细信息: ENUM 构造器 | 字段 | 方法

javax.persistence Enum FetchType

java.lang.Object
  java.lang.Enum<FetchType>
      javax.persistence.FetchType

所有已实现的接口:: Serializable, Comparable<FetchType>

public enum FetchType
extends Enum<FetchType>

Defines strategies for fetching data from the database. The EAGER strategy is a requirement on the persistence provider runtime that data must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime that data should be fetched lazily when it is first accessed. The implementation is permitted to eagerly fetch data for which the LAZY strategy hint has been specified. In particular, lazy fetching might only be available for Basic mappings for which property-based access is used.

   Example:
   @Basic(fetch=LAZY)
   protected String getName() { return name; }

从以下版本开始:: Java Persistence 1.0

Enum 常量摘要
`EAGER` Defines that data must be eagerly fetched
`LAZY` Defines that data can be lazily fetched

方法摘要
`static FetchType`	`valueOf(String name)` Returns the enum constant of this type with the specified name.
`static FetchType[]`	`values()` Returns an array containing the constants of this enum type, in the order they're declared.

类方法继承 java.lang.Enum
`clone, compareTo, equals, getDeclaringClass, hashCode, name, ordinal, toString, valueOf`

类方法继承 java.lang.Object
`finalize, getClass, notify, notifyAll, wait, wait, wait`

Enum 常量详细信息

LAZY

public static final FetchType LAZY

Defines that data can be lazily fetched

EAGER

public static final FetchType EAGER

Defines that data must be eagerly fetched

方法详细信息

values

public static final FetchType[] values()

Returns an array containing the constants of this enum type, in the order they're declared. This method may be used to iterate over the constants as follows:

for(FetchType c : FetchType.values())
        System.out.println(c);

返回:: an array containing the constants of this enum type, in the order they're declared

valueOf

public static FetchType valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

参数:: name - the name of the enum constant to be returned.
返回:: the enum constant with the specified name
抛出异常:: IllegalArgumentException - if this enum type has no constant with the specified name

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