```
@Target({METHOD,FIELD})
@Retention(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:

see GeneratedValue

注释类型 Id