如何解决没有基础表的休眠实体
我们一直在做这种事情-这是我们的做事方式:
-
定义一个简单的类似于bean的对象来表示报告中的每一行输出:
public class CityStateRevenueReport { private String mId; private String mState; private String mCity; private Double mRevenue; public String getId() { return mId; } public void setId(String i) { mId = i; } public String getState() { return mState; } public void setState(String s) { mState = s; } public String getCity() { return mCity; } public void setCity(String c) { mCity = c; } public Double getReveneue() { return mRevenue; } public void setRevneue(Double d) { mRevenue = d; }
}
-
定义一个hibernate映射文件CityStateRevneueReport.hbm.xml:
<?xml version="1.0" ?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class entity-name="CityStateRevenueReport">
<id name="Id" type="java.lang.String" column="report_id">
<generator class="sequence" />
</id>
<property name="city" type="string" column="city" />
<property name="state" type="string" column="state" />
<property name="revenue" type="double" column="revenue" />
</class>
<sql-query name="runReport">
<![CDATA[
SELECT {r.*} FROM
(select some_id_value as report_id,
state_abbreviation as state,
city_name as city,
dollar_amount as revenue
from -- tables, joins, other SQL insanity
) r
]]>
<return alias="r" class="CityStateRevenueReport" />
</sql-query>
</hibernate-mapping>
- 然后运行查询并填充实例:
public List<CityStateRevenueReport> runReport() { List<CityStateRevenueReport> reports = new ArrayList<CityStateRevenueReport>(); List<HashMap> maps = session.getNamedQuery("runReport").list() for ( HashMap map : results ) { CityStateRevenueReport report = new CityStateRevenueReport(); report.setState(map.get("state")); report.setCity(map.get("city")); report.setRevenue(Double.parseDouble(map.get("revenue")); reports.add(report); } return reports;
}
解决方法
我有一个非常丑陋的旧数据库系统,需要与之集成。本质上,我在系统上做一些只读报告,并且我不想建立代表我正在处理的每个表的上千个实体。相反,我只想为我生成的每种报告类型定义一个实体(本质上是来自不同表的一堆列的并集),然后让讨厌的hibernate映射(许多已加入,很多已合并)
sql查询到此类实体的列表。
问题是:我可以创建一个没有基础表的实体,并使用sql语句填充所述实体的列表吗?
谢谢!