Hibernate操纵视图详解

Hibernate操纵视图

①有如下视图：

图1

②hibernate逆向生成之后的代码如下：

CountView.java

 
 


  
  
package com.yaxing.entity;  

  
  
 

  
  
/**  

  
  
 * CountView entity. @author MyEclipse Persistence Tools  

  
  
 */ 

  
  
 

  
  
public class CountView implements java.io.Serializable {  

  
  
 

  
  
    // Fields  

  
  
 

  
  
    private CountViewId id;  

  
  
 

  
  
    // Constructors  

  
  
 

  
  
    /** default constructor */ 

  
  
    public CountView() {  

  
  
    }  

  
  
 

  
  
    /** full constructor */ 

  
  
    public CountView(CountViewId id) {  

  
  
        this.id = id;  

  
  
    }  

  
  
 

  
  
    // Property accessors  

  
  
 

  
  
    public CountViewId getId() {  

  
  
        return this.id;  

  
  
    }  

  
  
 

  
  
    public void setId(CountViewId id) {  

  
  
        this.id = id;  

  
  
    }  

  
  
 

  
  
} 
 
 

CountViewId.java

 
 


  
  
package com.yaxing.entity;  

  
  
 

  
  
/**  

  
  
 * CountViewId entity. @author MyEclipse Persistence Tools  

  
  
 */ 

  
  
 

  
  
public class CountViewId implements java.io.Serializable {  

  
  
 

  
  
    // Fields  

  
  
 

  
  
    private Integer countAthlete;  

  
  
    private Integer countTeam;  

  
  
    private long eveId;  

  
  
    private String race;  

  
  
    private long userId;  

  
  
    private long id;  

  
  
 

  
  
    // Constructors  

  
  
 

  
  
    /** default constructor */ 

  
  
    public CountViewId() {  

  
  
    }  

  
  
 

  
  
    /** minimal constructor */ 

  
  
    public CountViewId(long id) {  

  
  
        this.id = id;  

  
  
    }  

  
  
 

  
  
    /** full constructor */ 

  
  
    public CountViewId(Integer countAthlete, Integer countTeam, long eveId,  

  
  
            String race, long userId, long id) {  

  
  
        this.countAthlete = countAthlete;  

  
  
        this.countTeam = countTeam;  

  
  
        this.eveId = eveId;  

  
  
        this.race = race;  

  
  
        this.userId = userId;  

  
  
        this.id = id;  

  
  
    }  

  
  
 

  
  
    // Property accessors  

  
  
 

  
  
    public Integer getCountAthlete() {  

  
  
        return this.countAthlete;  

  
  
    }  

  
  
 

  
  
    public void setCountAthlete(Integer countAthlete) {  

  
  
        this.countAthlete = countAthlete;  

  
  
    }  

  
  
 

  
  
    public Integer getCountTeam() {  

  
  
        return this.countTeam;  

  
  
    }  

  
  
 

  
  
    public void setCountTeam(Integer countTeam) {  

  
  
        this.countTeam = countTeam;  

  
  
    }  

  
  
 

  
  
    public long getEveId() {  

  
  
        return this.eveId;  

  
  
    }  

  
  
 

  
  
    public void setEveId(long eveId) {  

  
  
        this.eveId = eveId;  

  
  
    }  

  
  
 

  
  
    public String getRace() {  

  
  
        return this.race;  

  
  
    }  

  
  
 

  
  
    public void setRace(String race) {  

  
  
        this.race = race;  

  
  
    }  

  
  
 

  
  
    public long getUserId() {  

  
  
        return this.userId;  

  
  
    }  

  
  
 

  
  
    public void setUserId(long userId) {  

  
  
        this.userId = userId;  

  
  
    }  

  
  
 

  
  
    public long getId() {  

  
  
        return this.id;  

  
  
    }  

  
  
 

  
  
    public void setId(long id) {  

  
  
        this.id = id;  

  
  
    }  

  
  
 

  
  
    public boolean equals(Object other) {  

  
  
        if ((this == other))  

  
  
            return true;  

  
  
        if ((other == null))  

  
  
            return false;  

  
  
        if (!(other instanceof CountViewId))  

  
  
            return false;  

  
  
        CountViewId castOther = (CountViewId) other;  

  
  
 

  
  
        return ((this.getCountAthlete() == castOther.getCountAthlete()) || (this 

  
  
                .getCountAthlete() != null 

  
  
                && castOther.getCountAthlete() != null && this 

  
  
                .getCountAthlete().equals(castOther.getCountAthlete())))  

  
  
                && ((this.getCountTeam() == castOther.getCountTeam()) || (this 

  
  
                        .getCountTeam() != null 

  
  
                        && castOther.getCountTeam() != null && this 

  
  
                        .getCountTeam().equals(castOther.getCountTeam())))  

  
  
                && (this.getEveId() == castOther.getEveId())  

  
  
                && ((this.getRace() == castOther.getRace()) || (this.getRace() != null 

  
  
                        && castOther.getRace() != null && this.getRace()  

  
  
                        .equals(castOther.getRace())))  

  
  
                && (this.getUserId() == castOther.getUserId())  

  
  
                && (this.getId() == castOther.getId());  

  
  
    }  

  
  
 

  
  
    public int hashCode() {  

  
  
        int result = 17;  

  
  
 

  
  
        result = 37 

  
  
                * result  

  
  
                + (getCountAthlete() == null ? 0 : this.getCountAthlete()  

  
  
                        .hashCode());  

  
  
        result = 37 * result  

  
  
                + (getCountTeam() == null ? 0 : this.getCountTeam().hashCode());  

  
  
        result = 37 * result + (int) this.getEveId();  

  
  
        result = 37 * result  

  
  
                + (getRace() == null ? 0 : this.getRace().hashCode());  

  
  
        result = 37 * result + (int) this.getUserId();  

  
  
        result = 37 * result + (int) this.getId();  

  
  
        return result;  

  
  
    }  

  
  
 

  
  
} 
 
 

我们知道，视图是没有主键的，视图就是一张虚拟表。hibernate对没有主键的表逆向生成的时候，是会生成

CountView.java

CountViewId.java

两个类的，XxxId.java这个类里面的属性才是我们需要的数据.

③映射文件如下：

CountView.hbm.xml

 
 


  
  
<?xml version="1.0" encoding="utf-8"?> 

  
  
<!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 Persistence Tools  

  
  
--> 

  
  
<hibernate-mapping> 

  
  
    <class name="com.yaxing.entity.CountView" table="countView" schema="dbo" catalog="sportSys"> 

  
  
        <composite-id name="id" class="com.yaxing.entity.CountViewId"> 

  
  
            <key-property name="countAthlete" type="integer"> 

  
  
                <column name="countAthlete" /> 

  
  
            </key-property> 

  
  
            <key-property name="countTeam" type="integer"> 

  
  
                <column name="countTeam" /> 

  
  
            </key-property> 

  
  
            <key-property name="eveId" type="long"> 

  
  
                <column name="eve_id" precision="18" scale="0" /> 

  
  
            </key-property> 

  
  
            <key-property name="race" type="string"> 

  
  
                <column name="race" length="50" /> 

  
  
            </key-property> 

  
  
            <key-property name="userId" type="long"> 

  
  
                <column name="userId" precision="18" scale="0" /> 

  
  
            </key-property> 

  
  
            <key-property name="id" type="long"> 

  
  
                <column name="id" precision="18" scale="0" /> 

  
  
            </key-property> 

  
  
        </composite-id> 

  
  
    </class> 

  
  
</hibernate-mapping> 
 
 

④CountViewDaoImpl .java如下：

 
 


  
  
package com.yaxing.daoImpl;  

  
  
 

  
  
import java.util.List;  

  
  
 

  
  
import org.hibernate.Query;  

  
  
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;  

  
  
 

  
  
import com.yaxing.dao.CountViewDao;  

  
  
import com.yaxing.entity.CountView;  

  
  
import com.yaxing.util.PageModel;  

  
  
 

  
  
public class CountViewDaoImpl extends HibernateDaoSupport implements CountViewDao {  

  
  
 

  
  
        @Override 

  
  
    public List<CountView> listCountView() {  

  
  
        // TODO Auto-generated method stub  

  
  
        return this.getHibernateTemplate().find("select id.countAthlete,id.countTeam,id.race,id.eveId from CountView");  

  
  
    }  

  
  
 

  
  
    }  
 
 

可以看到第17行：

 
 


  
  
return this.getHibernateTemplate().find("select id.countAthlete,id.countTeam,id.race,id.eveId from CountView"); 
 
 

字段是id.countAthlete这种，因为CountView.java的11行

 
 


  
  
private CountViewId id;   
 
 

我们这只有一个返回所有的List集合

⑤Action中如下：

 
 


  
  
public String listCountView() throws Exception {  

  
  
        try {  

  
  
            List allValue = this.countViewService.listCountView();  

  
  
            listCountView = new ArrayList();  

  
  
            Iterator it = allValue.iterator();  

  
  
            while (it.hasNext()) {  

  
  
                Object[] all = (Object[]) it.next();  

  
  
                CountViewId countViewId = new CountViewId();  

  
  
                countViewId.setCountAthlete((Integer) all[0]);  

  
  
                countViewId.setCountTeam((Integer) all[1]);  

  
  
                countViewId.setRace((String) all[2]);  

  
  
                countViewId.setEveId( (Long)all[3]);  

  
  
                  

  
  
                listCountView.add(countViewId);   

  
  
            }  

  
  
 

  
  
        } catch (Exception e) {  

  
  
            e.printStackTrace();  

  
  
            return INPUT;  

  
  
        }  

  
  
        return SUCCESS;  

  
  
 

  
  
    } 
 
 

第3行，如果直接写成

 
 


  
  
listCountView = this.countViewService.listCountView(); 
 
 

这个页面查询的是没有结果的！

是因为：Hibernate 映射视图会生成联合主键.在查询时,如果联合主键里有一项值为null,则整个结果返回null。然而，我们的查询中不可避免的存在值为null的情况，这种情况下该怎么办呢？

解决办法：需要做4-11行代码的转换才行！

给 listCountView 迭代的添加内容！

 本文转自 w156445045 51CTO博客，原文链接：http://blog.51cto.com/enetq/845699，如需转载请自行联系原作者