ColumnResult (Java EE 5)

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SUMMARY: REQUIRED | OPTIONAL

DETAIL: ELEMENT

javax.persistence Annotation Type ColumnResult

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

Implements: Annotation

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

SQL 查询的 SELECT 子句中列的引用名称（即列别名，如果适用）。通过在元数据中指定此注释，可以使查询结果中包含标量结果类型。

示例：
   Query q = em.createNativeQuery(
       "SELECT o.id AS order_id, " +
           "o.quantity AS order_quantity, " +
           "o.item AS order_item, " + 
           "i.name AS item_name, " +
         "FROM Order o, Item i " +
         "WHERE (order_quantity > 25) AND (order_item = i.id)",
       "OrderResults");

   @SqlResultSetMapping(name="OrderResults",
       entities={
           @EntityResult(entityClass=com.acme.Order.class, fields={
               @FieldResult(name="id", column="order_id"),
               @FieldResult(name="quantity", column="order_quantity"),
               @FieldResult(name="item", column="order_item")})},
       columns={
           @ColumnResult(name="item_name")}
       )

since

Java Persistence 1.0

英文文档：

References name of a column in the SELECT clause of a SQL query - i.e., column alias, if applicable. Scalar result types can be included in the query result by specifying this annotation in the metadata.

 Example:
   Query q = em.createNativeQuery(
       "SELECT o.id AS order_id, " +
           "o.quantity AS order_quantity, " +
           "o.item AS order_item, " + 
           "i.name AS item_name, " +
         "FROM Order o, Item i " +
         "WHERE (order_quantity > 25) AND (order_item = i.id)",
       "OrderResults");

   @SqlResultSetMapping(name="OrderResults",
       entities={
           @EntityResult(entityClass=com.acme.Order.class, fields={
               @FieldResult(name="id", column="order_id"),
               @FieldResult(name="quantity", column="order_quantity"),
               @FieldResult(name="item", column="order_item")})},
       columns={
           @ColumnResult(name="item_name")}
       )