关于hibernate的多对一、一对多双向映射

例子是city类和people类

双向关联映射：一个城市对应多个人；

多个人对应一个城市；

People.java

package com.pk.po;

public class People {
 private int id;
 private String name;
 private City city;
 
 
 public City getCity() {
  return city;
 }
 public void setCity(City city) {
  this.city = city;
 }
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }

}

City.java

package com.pk.po;

import java.util.Set;

public class City {
 private int id;
 private String name;
 private Set cityes;
 public Set getCityes() {
  return cityes;
 }
 public void setCityes(Set cityes) {
  this.cityes = cityes;
 }
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 
 
}

ORM映射文件：

People.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.pk.po">
 <class name="People" >
  <id name="id">
   <generator class="native"></generator>
  </id>
  <property name="name"></property>
  <many-to-one name="city" column="cityid"></many-to-one>
 </class>
 
</hibernate-mapping>

City.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.pk.po">
 <class name="City">
  <id name="id">
   <generator class="native"></generator>
  </id>
  <property name="name"></property>
  <set name="cityes" cascade="all" >

  <!--

  在一对多时，在多的一方所产生的列的名称，应与多对一时的列的名字是相同的

  -->
   <key column="cityid"></key>
   <one-to-many class="People" />
  </set>
 </class>
 
</hibernate-mapping>

hibernate.cfg.xml

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

<hibernate-configuration>
 <session-factory>
  <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
  <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_hql</property>
  <property name="hibernate.connection.username">root</property>
  <property name="hibernate.connection.password">root</property>
  <property name="show_sql">true</property>
  <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
  
  
  
  <mapping resource="com/pk/po/City.hbm.xml"/>
  <mapping resource="com/pk/po/People.hbm.xml"/>
 </session-factory>
</hibernate-configuration>