javax.persistence

## 注释类型 Id

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

  Specifies the primary key of an entity. The field or property to which the `Id` annotation is applied should be one of the following types: any Java primitive type; any primitive wrapper type; `String`; `java.util.Date`; `java.sql.Date`; `java.math.BigDecimal`; `java.math.BigInteger`.

  The mapped column for the primary key of the entity is assumed to be the primary key of the primary table. If no `Column` annotation is specified, the primary key column name is assumed to be the name of the primary key property or field.

         Example:

         @Id
         public Long getId() { return id; }

  从以下版本开始:
    Java Persistence 1.0
  另请参阅:
    `Column`, `GeneratedValue`