【JPA】JPA本地查询注解SqlResultSetMapping的使用


配置最后的形式:

@SqlResultSetMapping
(
        name = "ItemResults",
        entities = {
            @EntityResult(
                entityClass = Item.class, //就是当前这个类的名字
                fields = {
                    @FieldResult(name = "id", column = "id"),
                    @FieldResult(name = "itemId", column = "item_id"),
                }
            )
        },
        columns = {
            @ColumnResult(name = "item_id")
        }
)
@Entity
@Table(name="item_permission")
public class Item implements Serializable {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private String id;

    @Column(name="item_id")
    private Integer itemId;

    public Item(){}

}
查询

public ItemDAO{

ItemPermissionDAO dao = new ItemPermissionDAO();
        Query query = dao.getEntityManager().createNativeQuery(
                "select * from item_permission", "ItemResults");
        @SuppressWarnings("unchecked")
        List<Object[]> items = query.getResultList();
        for (Object[] item : items) {
            System.out.println(item[1]);
        }

}

它返回的格式是Object[]的数组形式

{ [, ] ,[, ] }

而且需要注意的是:

@EntityResult(
                entityClass = Item.class, //就是当前这个类的名字
                fields = {
                    @FieldResult(name = "id", column = "id"),
                    @FieldResult(name = "itemId", column = "item_id"),
                }
            )
其中注解FieldResult的配置必须是整个entity的所有属性的配置。在当前中属性有两个一个是id,另一个是itemId。所以FieldResult有两个。如果不写全的话,就会异常抛出。





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