EntityResult (Java EE 5)

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SUMMARY: REQUIRED | OPTIONAL

DETAIL: ELEMENT

javax.persistence Annotation Type EntityResult

@Target(value={}) @Retention(value=RUNTIME) public @interface EntityResult

Implements: Annotation

@Target(value={})
@Retention(value=RUNTIME)

引用 SQL 查询的 SELECT 子句中的实体。如果使用此注释，则 SQL 语句应该选择映射到该实体对象的所有列。这应该包括相关实体的外键列。数据不足时返回的结果是不确定的。

示例
   Query q = em.createNativeQuery(
       "SELECT o.id, o.quantity, o.item, i.id, i.name, i.description "+
           "FROM Order o, Item i " +
           "WHERE (o.quantity > 25) AND (o.item = i.id)",
       "OrderItemResults");
   @SqlResultSetMapping(name="OrderItemResults",
       entities={
           @EntityResult(entityClass=com.acme.Order.class),
           @EntityResult(entityClass=com.acme.Item.class)
   })

since

Java Persistence 1.0

英文文档：

References an entity in the SELECT clause of a SQL query. If this annotation is used, the SQL statement should select all of the columns that are mapped to the entity object. This should include foreign key columns to related entities. The results obtained when insufficient data is available are undefined.

   Example
   Query q = em.createNativeQuery(
       "SELECT o.id, o.quantity, o.item, i.id, i.name, i.description "+
           "FROM Order o, Item i " +
           "WHERE (o.quantity > 25) AND (o.item = i.id)",
       "OrderItemResults");
   @SqlResultSetMapping(name="OrderItemResults",
       entities={
           @EntityResult(entityClass=com.acme.Order.class),
           @EntityResult(entityClass=com.acme.Item.class)
   })

Since:: Java Persistence 1.0

Required Element Summary
`Class`	`entityClass` The class of the result

Optional Element Summary
`String`	`discriminatorColumn` Specifies the column name (or alias) of the column in the SELECT list that is used to determine the type of the entity instance.
`FieldResult[]`	`fields` Maps the columns specified in the SELECT list of the query to the properties or fields of the entity class.

Element Detail

abstract public Class<T> entityClass()
结果类

英文文档：
entityClass

public abstract Class entityClass

The class of the result

abstract public FieldResult[] fields()
将查询的 SELECT 列表中指定的列映射到实体类的属性或字段。

英文文档：
fields

public abstract FieldResult[] fields

Maps the columns specified in the SELECT list of the query to the properties or fields of the entity class.

Default:: {}

abstract public String discriminatorColumn()
指定 SELECT 列表中的列名称（或别名），该名称用于确定实体实例的类型。

英文文档：
discriminatorColumn

public abstract String discriminatorColumn

Specifies the column name (or alias) of the column in the SELECT list that is used to determine the type of the entity instance.

Default:: ""