在Hibernate应用中使用视图

Hibernate对于一些函数（如extract 、union，oracle数据库）不支持，导致用hql语句实现一些功能很麻烦，所以用了视图，
下面是在oracle数据库上的使用，工具MyEclipse。
1． 建立视图
例如：更加需要，建立视图cash_flow

create or replace view cash_flow as
select gather_date,description,gahter_sum,group_cn from actual_gather ag where(ag.gahter_sum>0) union all select expense_time,remark,(0 - expense_sum),group_cn from cash_expense ce where (ce.expense_sum >0) order by gather_date desc

2、导出类和配置文件
   在MyEclipse Database explorer视图下，点击右键可以建立数据库连接文件，成功连接上数据库后，在TABLE下面是常用的导出表所对应配置文件和java类功能。
即一个java基类AbstractModel.java，一个子类Model.java，和一个配置文件Model.hbm
而在VIEW下面，MyEclipse将把其中的视图当作表来导出。但导出的文件略有不同，多一个java类。
即AbstractCashFlow.java,CashFlow.java,CashFlowId.java,CashFlow.hbm等四个文件
其中CashFlowId类的属性就是视图的的属性，并以这些属性作为联合主键。
作为AbstractCashFlow的主键和唯一的属性. CashFlow继承这个父类。
下面为到出的代码

public class CashFlowId  implements java.io.Serializable {

    // Fields    
     private Date gatherDate;
     private String description;
     private Long gahterSum;
     private String groupCn;

    // Constructors

    /** default constructor */
    public CashFlowId() {
    }
    
    /** full constructor */
    public CashFlowId(Date gatherDate, String description, Long gahterSum, String groupCn) {
        this.gatherDate = gatherDate;
        this.description = description;
        this.gahterSum = gahterSum;
        this.groupCn = groupCn;
    }
    
   
    // Property accessors

    getter、setter方法
    .............

   public boolean equals(Object other) {
         if ( (this == other ) ) return true;
		 if ( (other == null ) ) return false;
		 if ( !(other instanceof CashFlowId) ) return false;
		 CashFlowId castOther = ( CashFlowId ) other; 
         
		 return ( (this.getGatherDate()==castOther.getGatherDate()) || ( this.getGatherDate()!=null && castOther.getGatherDate()!=null && this.getGatherDate().equals(castOther.getGatherDate()) ) )
 && ( (this.getDescription()==castOther.getDescription()) || ( this.getDescription()!=null && castOther.getDescription()!=null && this.getDescription().equals(castOther.getDescription()) ) )
 && ( (this.getGahterSum()==castOther.getGahterSum()) || ( this.getGahterSum()!=null && castOther.getGahterSum()!=null && this.getGahterSum().equals(castOther.getGahterSum()) ) )
 && ( (this.getGroupCn()==castOther.getGroupCn()) || ( this.getGroupCn()!=null && castOther.getGroupCn()!=null && this.getGroupCn().equals(castOther.getGroupCn()) ) );
   }
   
   public int hashCode() {
         int result = 17;
         
         result = 37 * result + ( getGatherDate() == null ? 0 : this.getGatherDate().hashCode() );
         result = 37 * result + ( getDescription() == null ? 0 : this.getDescription().hashCode() );
         result = 37 * result + ( getGahterSum() == null ? 0 : this.getGahterSum().hashCode() );
         result = 37 * result + ( getGroupCn() == null ? 0 : this.getGroupCn().hashCode() );
         return result;
   }   
}

public abstract class AbstractCashFlow  implements java.io.Serializable {

     private CashFlowId id;

    // Constructors
    /** default constructor */
    public AbstractCashFlow() {
    }

    /** full constructor */
    public AbstractCashFlow(CashFlowId id) {
        this.id = id;
    }
   
    // Property accessors

    public CashFlowId getId() {
        return this.id;
    }
    
    public void setId(CashFlowId id) {
        this.id = id;
    }
}

public class CashFlow extends AbstractCashFlow implements java.io.Serializable {
    // Constructors
    /** default constructor */
    public CashFlow() {
    }
    /** full constructor */
    public CashFlow(CashFlowId id) {
        super(id);        
    }    
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
    <class name="com.taiji.costmatrix.model.CashFlow" table="CASH_FLOW">
        <composite-id name="id" class="com.taiji.costmatrix.model.CashFlowId">
            <key-property name="gatherDate" type="java.util.Date">
                <column name="GATHER_DATE" length="7" />
            </key-property>
            <key-property name="description" type="java.lang.String">
                <column name="DESCRIPTION" length="1000" />
            </key-property>
            <key-property name="gahterSum" type="java.lang.Long">
                <column name="GAHTER_SUM" precision="22" scale="0" />
            </key-property>
            <key-property name="groupCn" type="java.lang.String">
                <column name="GROUP_CN" length="256" />
            </key-property>
        </composite-id>
    </class>
</hibernate-mapping>

3.调用
  别忘了将hbm文件的路径加到hibernate mapping那
  这是就可以直接在dao里hql语句读取,就像操作其他表一样.
  但须注意写法.

from CashFlow cf  where cf.id.groupCn=”T”

  也可以直接写sql
如

Select * from cash_flow

。