hibernate配置实战001

school和userMember是一对多关系,一些基本配置就不写了:
SchoolInfo.java

importjavax.persistence.CascadeType;
importjavax.persistence.Column;
importjavax.persistence.Entity;
importjavax.persistence.FetchType;
importjavax.persistence.GeneratedValue;
importjavax.persistence.Id;
importjavax.persistence.OneToMany;
importjavax.persistence.Table;
importjavax.persistence.Temporal;
importjavax.persistence.TemporalType;

importorg.hibernate.annotations.Formula;
importorg.hibernate.annotations.GenericGenerator;

@Entity
@Table(name="school_info")
publicclassSchoolInfoimplementsjava.io.Serializable{

@Id
@GeneratedValue(generator="system-uuid")
@GenericGenerator(name="system-uuid",strategy="uuid")
privateStringid;//hibernate的uuid机制,生成32为字符串

@Column(name="actcodeId",updatable=false,nullable=true,length=36)
privateStringactcodeId;

@Formula("selectCOUNT(*)fromschool_info")
privateintcount;

@Temporal(TemporalType.TIMESTAMP)//不用set,hibernate会自动把当前时间写入
@Column(updatable=false,length=20)
privateDatecreateTime;

@Temporal(TemporalType.TIMESTAMP)
privateDateupdateTime;//刚开始我默认insertable=false,但会读取出错提示如下:
//Value'0000-00-00'cannotberepresentedasjava.sql.Timestamp

// mappedBy="school"就相当于inverse=true,(mappedBy指定的是不需要维护关系的一端)
//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
@OneToMany(mappedBy="school",cascade=CascadeType.ALL,fetch=FetchType.EAGER,targetEntity=UserMember.class)
//用范性的话,就不用targetEntity了
privateList<usermember>users=</usermember>newArrayList<usermember>();</usermember>

}

@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)

@Entity
@Table(name="teacher_info")//实体类和数据库表名不一致时,才用这个
publicclassUserMemberimplementsjava.io.Serializable{

@Id
@GeneratedValue(generator="system-uuid")
@GenericGenerator(name="system-uuid",strategy="uuid")
privateStringid;

@Column(updatable=false,nullable=false,length=20)
privateStringlogonName;

@Temporal(TemporalType.TIMESTAMP)
@Column(updatable=false,length=20)
privateDatecreateTime;

@Temporal(TemporalType.TIMESTAMP)
privateDateupdateTime;

@ManyToOne(cascade={CascadeType.MERGE})
@JoinColumn(name="schoolId")
privateSchoolInfoschool;
//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.

}