当关联关系配置双向时，一方的set集合中inverse属性应设置为true。此时在级联操作时应将双方对象设置关联。 若关联关系为单向一对多时，inverse属性不可设置为true，用于保障级联操作时外键完整性。（和查询没关系，）
一：创建表
-- 创建部门和员工信息表 create table dept ( did number(7) primary key, deptName varchar2(20) not null ); create table emp ( eid number(7) primary key, empName varchar2(20) not null, deptid number(7) references dept(did) ); create sequence seq_dept; create sequence seq_emp; insert into dept values(seq_dept.nextval,'开发部'); insert into dept values(seq_dept.nextval,'测试部'); insert into dept values(seq_dept.nextval,'销售部'); commit; insert into emp values(seq_emp.nextval,'张三',1); insert into emp values(seq_emp.nextval,'李四',1); insert into emp values(seq_emp.nextval,'王五',2); insert into emp values(seq_emp.nextval,'赵六',2); insert into emp values(seq_emp.nextval,'孙七',3); insert into emp values(seq_emp.nextval,'老八',3); insert into emp values(seq_emp.nextval,'小九',3); commit; select * from dept; select * from emp; select * from emp where eid = 4 select * from dept where did = 2 insert int dept values(5,'行政部'); insert int emp values(10,'行政人员1',null); insert int emp values(11,'行政人员1',null); update emp set deptid = 5 where eid = 10; update emp set deptid = 5 where eid = 11;实体类
package entity; import java.io.Serializable; import java.util.HashSet; import java.util.Set; /* * hibernate实体类 */ public class Dept implements Serializable { private Integer did; private String deptName; //增加关联集合属性（一对多）//在1的一方，表达持有多的一方的引用=》使用集合(一个部门有多个人员)(这个在一对多的时候用的。比如查找某个部门下的员工) private Set<Emp> empSet=new HashSet<Emp>() ;//查找某个员工在那个部门用不到这个（多对一） public Dept() { super(); // TODO Auto-generated constructor stub } public Dept(Integer did, String deptName, Set<Emp> empSet) { super(); this.did = did; this.deptName = deptName; this.empSet = empSet; } public Integer getDid() { return did; } public void setDid(Integer did) { this.did = did; } public String getDeptName() { return deptName; } public void setDeptName(String deptName) { this.deptName = deptName; } public Set<Emp> getEmpSet() { return empSet; } public void setEmpSet(Set<Emp> empSet) { this.empSet = empSet; } } emp实体类 package entity; import java.io.Serializable; public class Emp implements Serializable { private Integer eid; private String empName; //private Dept dept; 外键，在这里不用这，直接管理另一个类的属性 private Dept dept;//关联属性 public Emp(){ } public Emp(Integer eid, String empName, Dept dept) { super(); this.eid = eid; this.empName = empName; this.dept = dept; } public Integer getEid() { return eid; } public void setEid(Integer eid) { this.eid = eid; } public String getEmpName() { return empName; } public void setEmpName(String empName) { this.empName = empName; } public Dept getDept() { return dept; } public void setDept(Dept dept) { this.dept = dept; } } 二：配置文件 <?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <!-- Generated by MyEclipse Hibernate Tools. --> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.OracleDialect</property> <property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property> <property name="connection.username">system</property> <property name="connection.password">password</property> <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property> <property name="show_sql">true</property> <property name="format_sql">true</property> <mapping resource="entity/Dept.hbm.xml"/><!-- 这个是写好Emp.hbm.xml配置文件后在写回来 --> <mapping resource="entity/Emp.hbm.xml"/> </session-factory> </hibernate-configuration> 三：配置实体类与表的映射文件（本次测试是：emp表与的dept表，emp表中引用了dept表的主键作为外键。测试可以通过查询emp表查找某个人员在哪个部门）
在emp表中设置一对多的映射关系。多个员工对应一个部门。 many—to-one name是部门表的表名（多员工对应一个部门，哪个one后面就是要对应的一的那个部门表 class 也是部门表的实体类。注意那个column里写的是emp表中的外键）
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" > <hibernate-mapping> <class name="entity.Emp" table="Emp"> <id name="eid" > <generator class="sequence"> <param name="sequence">seq_emp</param> </generator> </id> <property name="empName"></property> <!--配置多对一映射关系 --> <!-- emp表中的外键 --> <many-to-one name="dept" class="entity.Dept" column="DEPTID"/> </class> </hibernate-mapping>dept表
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" > <hibernate-mapping> <class name="entity.Dept" table="dept"> <id name="did" column="did "> <generator class="sequence"> <param name="sequence"> seq_dept </param> </generator> </id> <property name="deptName"></property> <!-- 这个属性不要写错了是property --> </class> </hibernate-mapping> 测试类 package Test; import org.hibernate.Session; import entity.Emp; import Util.HibernateUtil; public class Test { public static void main(String[] args) { Session session = HibernateUtil.currentSesion(); Emp emp=(Emp) session.load(Emp.class,4); System.out.println(emp.getEmpName()+"所在部门为："+emp.getDept().getDeptName()); } }
