Hibernate中的關系映射，最常見的關系映射之一就是一對多關系映射例如學生與班級的關系，一個班級對應多個學生。如圖：  Hibernate中如何來映射這兩個的關系呢？ 下面就為大家講解一下： 1、創建實體類Classes和實體類Student Classes.java ~~~ package com.bjpowernode.hibernate; import java.util.Set; public class Classes { private int id; private String name; private Set students; 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; } public Set getStudents() { return students; } public void setStudents(Set students) { this.students = students; } } ~~~ Student.java ~~~ package com.bjpowernode.hibernate; public class Student { private int id; private String name; private Classes classes; 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; } public Classes getClasses() { return classes; } public void setClasses(Classes classes) { this.classes = classes; } } ~~~ 2、創建映射文件Classes.hbm.xml和Student.hbm.xml Classes.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> <class name="com.bjpowernode.hibernate.Classes" table="t_classes"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <set name="students" inverse="true"> <!-- <key column="classesid" not-null="true"/> --> <key column="classesid"/> <one-to-many class="com.bjpowernode.hibernate.Student"/> </set> </class> </hibernate-mapping> ~~~ Student.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> <class name="com.bjpowernode.hibernate.Student" table="t_student"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <many-to-one name="classes" column="classesid"/> </class> </hibernate-mapping> ~~~ 3、效果圖  PS：我上面舉例的是一對多雙向關聯的例子。有雙向關聯當然就有單向關聯。下面舉個例子來說明他們的區別 如果Student添加了一條記錄當中的classesid在Classes中沒有這個id，雙向關聯的話則先添加學生這條記錄然后再班級那里添加這個班級，然后再更新學生的classesid。單向關聯的話先添加班級，然后再添加學生。