Hibernate一对多双向annotation配置

Hibernate一对多双向annotation配置

摘自： http://www.javaeye.com/topic/95822

school和userMember是一对多关系：

SchoolInfo.java

 1 import  javax.persistence.CascadeType;   
 2 import  javax.persistence.Column;   
 3 import  javax.persistence.Entity;   
 4 import  javax.persistence.FetchType;   
 5 import  javax.persistence.GeneratedValue;   
 6 import  javax.persistence.Id;   
 7 import  javax.persistence.OneToMany;   
 8 import  javax.persistence.Table;   
 9 import  javax.persistence.Temporal;   
10 import  javax.persistence.TemporalType;   
11    
12 import  org.hibernate.annotations.Formula;   
13 import  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机制,生成32为字符串   
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会自动把当前时间写入   
31    @Column(updatable = false, length = 20)   
32    private Date createTime;   
33   
34    @Temporal(TemporalType.TIMESTAMP)   
35    private Date updateTime;// 刚开始我默认insertable=false,但会读取出错提示如下:   
36    // Value '0000-00-00' can not be represented as java.sql.Timestamp   
37   
38    // mappedBy="school"就相当于inverse=true,(mappedBy指定的是不需要维护关系的一端)   
39    // 应该注意的是mappedBy值对应@ManyToOne标注的属性,我刚开始写成"schoolId",让我郁闷了好一会 
40    @OneToMany(mappedBy = "school", cascade = CascadeType.ALL, fetch = FetchType.EAGER, targetEntity = UserMember.class)   
41    // 用范性的话,就不用targetEntity了   
42    private List<usermember> users = </usermember>new ArrayList<usermember>();  </usermember> 
43       
44}    
45

@GeneratedValue(strategy=GenerationType.AUTO)我们常用的自增长机制,我这里采用的是hibernate的uuid生成机制.
需要注意的是import javax.xx.Entity ，而不是org.hibernate.xx.Entity。
郁闷的是我上面用到@Formula,生成的sql竟然是'select COUNT(*) from school_info as formula0_ from school_info schoolinfo0_,当然不能执行了,寻求正解中~!!!!!!!!!

UserMember.java(前面引入的包已经贴过了,下面就不贴了)

 1  @Entity   
 2  @Table(name  =   " teacher_info " ) // 实体类和数据库表名不一致时,才用这个   
 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       // 注意该类就不用声明schoolId属性了,如果不用@JoinColumn指明关联的字段,hibernate默认会是school_id.   
24     
25  }