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

1. package com.yaxing.entity;  
2.  
3. /**  
4.  * CountView entity. @author MyEclipse Persistence Tools  
5.  */ 
6.  
7. public class CountView implements java.io.Serializable {  
8.  
9.     // Fields  
10.  
11.     private CountViewId id;  
12.  
13.     // Constructors  
14.  
15.     /** default constructor */ 
16.     public CountView() {  
17.     }  
18.  
19.     /** full constructor */ 
20.     public CountView(CountViewId id) {  
21.         this.id = id;  
22.     }  
23.  
24.     // Property accessors  
25.  
26.     public CountViewId getId() {  
27.         return this.id;  
28.     }  
29.  
30.     public void setId(CountViewId id) {  
31.         this.id = id;  
32.     }  
33.  
34. } 

CountViewId.java

1. package com.yaxing.entity;  
2.  
3. /**  
4.  * CountViewId entity. @author MyEclipse Persistence Tools  
5.  */ 
6.  
7. public class CountViewId implements java.io.Serializable {  
8.  
9.     // Fields  
10.  
11.     private Integer countAthlete;  
12.     private Integer countTeam;  
13.     private long eveId;  
14.     private String race;  
15.     private long userId;  
16.     private long id;  
17.  
18.     // Constructors  
19.  
20.     /** default constructor */ 
21.     public CountViewId() {  
22.     }  
23.  
24.     /** minimal constructor */ 
25.     public CountViewId(long id) {  
26.         this.id = id;  
27.     }  
28.  
29.     /** full constructor */ 
30.     public CountViewId(Integer countAthlete, Integer countTeam, long eveId,  
31.             String race, long userId, long id) {  
32.         this.countAthlete = countAthlete;  
33.         this.countTeam = countTeam;  
34.         this.eveId = eveId;  
35.         this.race = race;  
36.         this.userId = userId;  
37.         this.id = id;  
38.     }  
39.  
40.     // Property accessors  
41.  
42.     public Integer getCountAthlete() {  
43.         return this.countAthlete;  
44.     }  
45.  
46.     public void setCountAthlete(Integer countAthlete) {  
47.         this.countAthlete = countAthlete;  
48.     }  
49.  
50.     public Integer getCountTeam() {  
51.         return this.countTeam;  
52.     }  
53.  
54.     public void setCountTeam(Integer countTeam) {  
55.         this.countTeam = countTeam;  
56.     }  
57.  
58.     public long getEveId() {  
59.         return this.eveId;  
60.     }  
61.  
62.     public void setEveId(long eveId) {  
63.         this.eveId = eveId;  
64.     }  
65.  
66.     public String getRace() {  
67.         return this.race;  
68.     }  
69.  
70.     public void setRace(String race) {  
71.         this.race = race;  
72.     }  
73.  
74.     public long getUserId() {  
75.         return this.userId;  
76.     }  
77.  
78.     public void setUserId(long userId) {  
79.         this.userId = userId;  
80.     }  
81.  
82.     public long getId() {  
83.         return this.id;  
84.     }  
85.  
86.     public void setId(long id) {  
87.         this.id = id;  
88.     }  
89.  
90.     public boolean equals(Object other) {  
91.         if ((this == other))  
92.             return true;  
93.         if ((other == null))  
94.             return false;  
95.         if (!(other instanceof CountViewId))  
96.             return false;  
97.         CountViewId castOther = (CountViewId) other;  
98.  
99.         return ((this.getCountAthlete() == castOther.getCountAthlete()) || (this 
100.                 .getCountAthlete() != null 
101.                 && castOther.getCountAthlete() != null && this 
102.                 .getCountAthlete().equals(castOther.getCountAthlete())))  
103.                 && ((this.getCountTeam() == castOther.getCountTeam()) || (this 
104.                         .getCountTeam() != null 
105.                         && castOther.getCountTeam() != null && this 
106.                         .getCountTeam().equals(castOther.getCountTeam())))  
107.                 && (this.getEveId() == castOther.getEveId())  
108.                 && ((this.getRace() == castOther.getRace()) || (this.getRace() != null 
109.                         && castOther.getRace() != null && this.getRace()  
110.                         .equals(castOther.getRace())))  
111.                 && (this.getUserId() == castOther.getUserId())  
112.                 && (this.getId() == castOther.getId());  
113.     }  
114.  
115.     public int hashCode() {  
116.         int result = 17;  
117.  
118.         result = 37 
119.                 * result  
120.                 + (getCountAthlete() == null ? 0 : this.getCountAthlete()  
121.                         .hashCode());  
122.         result = 37 * result  
123.                 + (getCountTeam() == null ? 0 : this.getCountTeam().hashCode());  
124.         result = 37 * result + (int) this.getEveId();  
125.         result = 37 * result  
126.                 + (getRace() == null ? 0 : this.getRace().hashCode());  
127.         result = 37 * result + (int) this.getUserId();  
128.         result = 37 * result + (int) this.getId();  
129.         return result;  
130.     }  
131.  
132. } 

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

1. <?xml version="1.0" encoding="utf-8"?> 
2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"  
3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 
4. <!--   
5.     Mapping file autogenerated by MyEclipse Persistence Tools  
6. --> 
7. <hibernate-mapping> 
8.     <class name="com.yaxing.entity.CountView" table="countView" schema="dbo" catalog="sportSys"> 
9.         <composite-id name="id" class="com.yaxing.entity.CountViewId"> 
10.             <key-property name="countAthlete" type="integer"> 
11.                 <column name="countAthlete" /> 
12.             </key-property> 
13.             <key-property name="countTeam" type="integer"> 
14.                 <column name="countTeam" /> 
15.             </key-property> 
16.             <key-property name="eveId" type="long"> 
17.                 <column name="eve_id" precision="18" scale="0" /> 
18.             </key-property> 
19.             <key-property name="race" type="string"> 
20.                 <column name="race" length="50" /> 
21.             </key-property> 
22.             <key-property name="userId" type="long"> 
23.                 <column name="userId" precision="18" scale="0" /> 
24.             </key-property> 
25.             <key-property name="id" type="long"> 
26.                 <column name="id" precision="18" scale="0" /> 
27.             </key-property> 
28.         </composite-id> 
29.     </class> 
30. </hibernate-mapping> 

④CountViewDaoImpl .java如下：

1. package com.yaxing.daoImpl;  
2.  
3. import java.util.List;  
4.  
5. import org.hibernate.Query;  
6. import org.springframework.orm.hibernate3.support.HibernateDaoSupport;  
7.  
8. import com.yaxing.dao.CountViewDao;  
9. import com.yaxing.entity.CountView;  
10. import com.yaxing.util.PageModel;  
11.  
12. public class CountViewDaoImpl extends HibernateDaoSupport implements CountViewDao {  
13.  
14.         @Override 
15.     public List<CountView> listCountView() {  
16.         // TODO Auto-generated method stub  
17.         return this.getHibernateTemplate().find("select id.countAthlete,id.countTeam,id.race,id.eveId from CountView");  
18.     }  
19.  
20.     }  

可以看到第17行：

1. 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

1. private CountViewId id;   

我们这只有一个返回所有的List集合

⑤Action中如下：

1. public String listCountView() throws Exception {  
2.         try {  
3.             List allValue = this.countViewService.listCountView();  
4.             listCountView = new ArrayList();  
5.             Iterator it = allValue.iterator();  
6.             while (it.hasNext()) {  
7.                 Object[] all = (Object[]) it.next();  
8.                 CountViewId countViewId = new CountViewId();  
9.                 countViewId.setCountAthlete((Integer) all[0]);  
10.                 countViewId.setCountTeam((Integer) all[1]);  
11.                 countViewId.setRace((String) all[2]);  
12.                 countViewId.setEveId( (Long)all[3]);  
13.                   
14.                 listCountView.add(countViewId);   
15.             }  
16.  
17.         } catch (Exception e) {  
18.             e.printStackTrace();  
19.             return INPUT;  
20.         }  
21.         return SUCCESS;  
22.  
23.     } 

第3行，如果直接写成

1. 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