摘自：http://www.javaeye.com/topic/95822
school和userMember是一對(duì)多關(guān)系：
SchoolInfo.java
1
import javax.persistence.CascadeType;
2import javax.persistence.Column;
3import javax.persistence.Entity;
4import javax.persistence.FetchType;
5import javax.persistence.GeneratedValue;
6import javax.persistence.Id;
7import javax.persistence.OneToMany;
8import javax.persistence.Table;
9import javax.persistence.Temporal;
10import javax.persistence.TemporalType;
11
12import org.hibernate.annotations.Formula;
13import org.hibernate.annotations.GenericGenerator;
14
15@Entity
16@Table(name = "school_info")
17
public class SchoolInfo implements java.io.Serializable 
{
18
19 @Id
20 @GeneratedValue(generator = "system-uuid")
21 @GenericGenerator(name = "system-uuid", strategy = "uuid")
22 private String id;//hibernate的uuid機(jī)制,生成32為字符串
23
24 @Column(name = "actcodeId", updatable = false, nullable = true, length = 36)
25 private String actcodeId;
26
27 @Formula("select COUNT(*) from school_info")
28 private int count;
29
30 @Temporal(TemporalType.TIMESTAMP)//不用set,hibernate會(huì)自動(dòng)把當(dāng)前時(shí)間寫入
31 @Column(updatable = false, length = 20)
32 private Date createTime;
33
34 @Temporal(TemporalType.TIMESTAMP)
35 private Date updateTime;// 剛開始我默認(rèn)insertable=false,但會(huì)讀取出錯(cuò)提示如下:
36 // Value '0000-00-00' can not be represented as java.sql.Timestamp
37
38 // mappedBy="school"就相當(dāng)于inverse=true,(mappedBy指定的是不需要維護(hù)關(guān)系的一端)
39 // 應(yīng)該注意的是mappedBy值對(duì)應(yīng)@ManyToOne標(biāo)注的屬性,我剛開始寫成"schoolId",讓我郁悶了好一會(huì)
40 @OneToMany(mappedBy = "school", cascade = CascadeType.ALL, fetch = FetchType.EAGER, targetEntity = UserMember.class)
41 // 用范性的話,就不用targetEntity了
42 private List<usermember> users = </usermember>new ArrayList<usermember>(); </usermember>
43
44
}
45
@GeneratedValue(strategy=GenerationType.AUTO)我們常用的自增長(zhǎng)機(jī)制,我這里采用的是hibernate的uuid生成機(jī)制.
需要注意的是import javax.xx.Entity ，而不是org.hibernate.xx.Entity。
郁悶的是我上面用到@Formula,生成的sql竟然是'select COUNT(*) from school_info as formula0_ from school_info schoolinfo0_,當(dāng)然不能執(zhí)行了,尋求正解中~!!!!!!!!!
UserMember.java(前面引入的包已經(jīng)貼過(guò)了,下面就不貼了)
1 @Entity
2 @Table(name = "teacher_info")//實(shí)體類和數(shù)據(jù)庫(kù)表名不一致時(shí),才用這個(gè)
3 public class UserMember implements java.io.Serializable {
4
5 @Id
6 @GeneratedValue(generator = "system-uuid")
7 @GenericGenerator(name = "system-uuid", strategy = "uuid")
8 private String id;
9
10 @Column(updatable = false, nullable = false, length = 20)
11 private String logonName;
12
13 @Temporal(TemporalType.TIMESTAMP)
14 @Column(updatable = false, length = 20)
15 private Date createTime;
16
17 @Temporal(TemporalType.TIMESTAMP)
18 private Date updateTime;
19
20 @ManyToOne(cascade = { CascadeType.MERGE })
21 @JoinColumn(name = "schoolId")
22 private SchoolInfo school;
23 //注意該類就不用聲明schoolId屬性了,如果不用@JoinColumn指明關(guān)聯(lián)的字段,hibernate默認(rèn)會(huì)是school_id.
24
25 }
posted on 2009-07-26 13:40
jiafang83 閱讀(3185)
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