Basic (Java EE 5)

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SUMMARY: REQUIRED | OPTIONAL

DETAIL: ELEMENT

javax.persistence Annotation Type Basic

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

Implements: Annotation

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

Basic 注释是数据库列最简单的映射类型。Basic 注释可以应用于以下任意类型的持久属性或实例变量：Java 基本类型、基本类型的包装器、String、java.math.BigInteger、java.math.BigDecimal、java.util.Date、java.util.Calendar、java.sql.Date、java.sql.Time、java.sql.Timestamp、byte[], Byte[], char[], Character[]、枚举以及任何实现 Serializable 的其他类型。

对于这些类型的持久字段和属性，使用 Basic 注释是可选的。

since

Java Persistence 1.0

英文文档：

The Basic annotation is the simplest type of mapping to a database column. The Basic annotation can be applied to a persistent property or instance variable of any of the following types: Java primitive types, wrappers of the primitive types, String, java.math.BigInteger, java.math.BigDecimal, java.util.Date, java.util.Calendar, java.sql.Date, java.sql.Time, java.sql.Timestamp, byte[], Byte[], char[], Character[], enums, and any other type that implements Serializable.

The use of the Basic annotation is optional for persistent fields and properties of these types.

Since:: Java Persistence 1.0

Optional Element Summary
`FetchType`	`fetch` (Optional) Defines whether the value of the field or property should be lazily loaded or must be eagerly fetched.
`boolean`	`optional` (Optional) Defines whether the value of the field or property may be null.

abstract public FetchType fetch()
（可选）定义字段或属性的值是应该延迟加载还是必须立即获取。使用 `EAGER` 战略是必须立即获取值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。如果没有指定，则默认为 `EAGER`。

英文文档：
fetch

public abstract FetchType fetch

(Optional) Defines whether the value of the field or property should be lazily loaded or must be eagerly fetched. The EAGER strategy is a requirement on the persistence provider runtime that the value must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime. If not specified, defaults to EAGER.

Default:: EAGER

abstract public boolean optional()
（可选）定义字段或属性的值是否可以为 null。这是一个提示，基础类型可以忽略；它可以用于模式生成。如果没有指定，则默认为 `true`。

英文文档：
optional

public abstract boolean optional

(Optional) Defines whether the value of the field or property may be null. This is a hint and is disregarded for primitive types; it may be used in schema generation. If not specified, defaults to true.