关于hibernate的多对一、一对多双向映射
例子是city类和people类
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双向关联映射：一个城市对应多个人；
多个人对应一个城市；
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People.java
package com.pk.po;
public class People {
?private int id;
?private String name;
?private City city;
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?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;
?}
}
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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;
?}
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}
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 column="cityid"></many-to-one>
?</class>
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</hibernate-mapping>
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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 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 />
??</set>
?</class>
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</hibernate-mapping>
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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>
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??
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??<mapping resource="com/pk/po/City.hbm.xml"/>
??<mapping resource="com/pk/po/People.hbm.xml"/>
?</session-factory>
</hibernate-configuration>
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