Java SqlResultsMapping列作为和实体
我真的很困惑,列结果集映射是如何工作的?当我使用列而不是实体时,映射的是什么?看看这个例子Java SqlResultsMapping列作为和实体,java,jpa,entities,sqlresultsetmapping,Java,Jpa,Entities,Sqlresultsetmapping,我真的很困惑,列结果集映射是如何工作的?当我使用列而不是实体时,映射的是什么?看看这个例子 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, " + "FRO
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")}
)
我可以理解他在这里试图做什么,实体结果将是他想要的结果集,字段将尝试将字段映射到别名,列结果到底在做什么?看起来它没有映射到任何东西 将结果集中的4个字段映射到2个Java类:第一个类是Order实体,第二个类(可能)是包含“item_name”db字段的字符串
DB: Java
--- ----
order_id ---> \
order_quantity ---> Order entity
order_item ---> /
item_name ---> String
要读取查询结果,请执行以下操作:
for (Object[] record : query.getResultList()) {
Order order = (Order)record[0];
String itemName = (String)record[1];
}