Hibernateday04一对多的自身相关(从员工找经理)

对多的自身相关
   以Emp表为例:一个雇员会有多个下属，一个雇员也只能有一个上级


从员工找经理(1:1)
class Emp{//配置员工
 Integer empNo  
 String eName                    
 String job                       
 Emp mrg //经理也是员工，我们需要获得是Emp而不是一个经理的empNo           
 Date  hireDate                      
 Double sal  //如果表当中的该字段允许为null ,对象中应该使用封装类     
 Double comm                         
 Integer deptNo
}

 

1.建表（R），使用oracle提供的emp表

EMPNO                          NOT NULL NUMBER(4)                                                                                                                                                                                     
ENAME                                   VARCHAR2(10)                                                                                                                                                                                  
JOB                                     VARCHAR2(9)                                                                                                                                                                                   
MGR                                     NUMBER(4)                                                                                                                                                                                     
HIREDATE                                DATE                                                                                                                                                                                          
SAL                                     NUMBER(7,2)                                                                                                                                                                                   
COMM                                    NUMBER(7,2)                                                                                                                                                                                   
DEPTNO                                  NUMBER(2)        

 2.（O）在com.jsu.hb.pojo包中提供实体类Emp

package com.jsu.hb.pojo;

import java.util.Date;

public class Emp {
	private Integer empNo;
	private String  ename;
	private String job;
	private Emp mgr;
	private Date hireDate;
	private Double sal;
	private Double comm;
	private Integer deptNo;
	public Integer getEmpNo() {
		return empNo;
	}
	public void setEmpNo(Integer empNo) {
		this.empNo = empNo;
	}
	public String getEname() {
		return ename;
	}
	public void setEname(String ename) {
		this.ename = ename;
	}
	public String getJob() {
		return job;
	}
	public void setJob(String job) {
		this.job = job;
	}
	public Emp getMgr() {
		return mgr;
	}
	public void setMgr(Emp mgr) {
		this.mgr = mgr;
	}
	public Date getHireDate() {
		return hireDate;
	}
	public void setHireDate(Date hireDate) {
		this.hireDate = hireDate;
	}
	public Double getSal() {
		return sal;
	}
	public void setSal(Double sal) {
		this.sal = sal;
	}
	public Double getComm() {
		return comm;
	}
	public void setComm(Double comm) {
		this.comm = comm;
	}
	public Integer getDeptNo() {
		return deptNo;
	}
	public void setDeptNo(Integer deptNo) {
		this.deptNo = deptNo;
	}
	
	
}

 3.提供映射文件(M),emp.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.jsu.hb.pojo"><!-- 配置当前xml的默认包路径 -->
	<class name="Emp" table="emp">
		<!-- 配置主键信息 -->
		<id name="empNo" column="empno" type="java.lang.Integer">
			<generator class="increment"></generator>
		</id>
		<!-- 配置普通属性 -->
		<property name="ename" column="ename" type="string"></property><!--hibernate定义的类型  -->
		<property name="job" column="job"></property><!--type可以省略  -->
		<property name="hireDate" column="hiredate" type="java.util.Date"></property>
		<property name="sal" column="sal"></property>
		<property name="comm" column="comm"></property>
		<property name="deptNo" column="deptno"></property>
	<!-- 关系属性 多个员工对应一个经理 -->
		<many-to-one name="mgr" class="Emp" column="mgr" cascade="save-update"></many-to-one>
	</class>
</hibernate-mapping>

 4.在hibernate.cfg.xml文件中给映射文件注册

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory> 
		<!-- show_sql:是否显示hibernate执行的SQL语句，默认为false -->
		<property name="show_sql">true</property>
		<!-- show_sql:是否显示hibernate执行格式化输出的SQL语句，默认为false -->
		<property name="format_sql">true</property>
		<!-- 配置与数据库连接的参数 -->
		<property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
		<property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>
		<property name="connection.username">scott</property>
		<property name="connection.password">tiger</property>
		<!-- 2.自身属性相关的配置
			dialect:方言
			hibernate根据dialect的配置进行特定数据性能方面的调优
		 -->
		<property name="dialect">org.hibernate.dialect.Oracle9iDialect</property>
		<mapping resource="com/jsu/hb/pojo/emp.hbm.xml"></mapping>
	</session-factory>
</hibernate-configuration>

 5.提供工具类获得Session

package com.jsu.hb.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
	private static SessionFactory sf;
	private static ThreadLocal<Session> tl= new ThreadLocal<Session>();
	static{
		try{
				Configuration cfg = new Configuration();
				cfg.configure();
				sf=cfg.buildSessionFactory();
		}catch(Exception e){
			e.printStackTrace();
		}
	}
	public static Session openSession(){
		return sf.openSession();
	}
	public static Session getCurrentSession(){
		Session session = tl.get();//先从储存的线程中查找
		if(session==null){
			session=openSession();
			tl.set(session);
			return session;
		}
		return session;
	}
}

 6.提供测试类TestfindMgr.java

package com.jsu.hb.test;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.jsu.hb.pojo.Emp;
import com.jsu.hb.util.HibernateUtil;

public class TestfindMgr {
	@Test
	public void findMgr(){
		Session session = HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		Emp e =(Emp)session.get(Emp.class, 7654);
		System.out.println(e.getMgr().getEname());
		tx.commit();
	}
}