package cn.itcast.hiberate.sh.domain;public class Student {    private Long sid;    private String sname;    private String description;    public Long getSid() {        return sid;    }    public void setSid(Long sid) {        this.sid = sid;    }    public String getSname() {        return sname;    }    public void setSname(String sname) {        this.sname = sname;    }    public String getDescription() {        return description;    }    public void setDescription(String description) {        this.description = description;    }    @Override    public String toString() {        return "Student [sid=" + sid + ", sname=" + sname + ", description="                + description + "]";    }    }

package cn.itcast.hiberate.sh.domain;import java.util.Set;public class Classes {    private Long cid;    private String cname;    private String description;    private Set<Student> students;    public Long getCid() {        return cid;    }    public void setCid(Long cid) {        this.cid = cid;    }    public String getCname() {        return cname;    }    public void setCname(String cname) {        this.cname = cname;    }    public String getDescription() {        return description;    }    public void setDescription(String description) {        this.description = description;    }    public Set<Student> getStudents() {        return students;    }    @Override    public String toString() {        return "Classes [cid=" + cid + ", cname=" + cname + ", description="                + description + ", students=" + students + "]";    }    public void setStudents(Set<Student> students) {        this.students = students;    }    }

<?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>    <!-- name的值代表的是一个实体 -->    <class name="cn.itcast.hiberate.sh.domain.Student">        <!-- id用于指定主键  column,主键在数据库表列 ，  increment,主键自增 -->        <!-- length,指定长度 type,类型，也可以不写 -->        <id name="sid" length="5" type="java.lang.Long">            <generator class="increment"></generator>        </id>        <!-- 表示表中普通的属性 -->        <property name="sname" length="20" type="java.lang.String"></property>        <property name="description" length="100" type="java.lang.String"></property>    </class></hibernate-mapping>

<?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>    <!-- name的值代表的是一个实体 -->    <class name="cn.itcast.hiberate.sh.domain.Classes">        <!-- id用于指定主键  column,主键在数据库表列 ，  increment,主键自增 -->        <!-- length,指定长度 type,类型，也可以不写 -->        <id name="cid" length="5" type="java.lang.Long">            <generator class="increment"></generator>        </id>        <!-- 表示表中普通的属性 -->        <property name="cname" length="20" type="java.lang.String"></property>        <property name="description" length="100" type="java.lang.String"></property>        <!-- set元素和实体类中的 private Set<Student> students; 相对应 -->        <!--             set元素对应类中的set集合            通过set元素使classes表与student表建立关联               key是通过外键的形式让两张表建立关联               one-to-many是通过类的形式让两个类建立关联                        cascade 级联               save-update                   1、当 保存班级的时候，对学生进行怎么样的操作                        如果学生对象在数据库中没有对应的值，这个时候会执行save操作                        如果学生对象在数据库中有对应的值，这个时候会执行update操作               delete               all            inverse  维护关系               true      不维护关系                    false     维护关系               default   false         -->        <set name="students" cascade="save-update">            <!--                 key是用来描述外键             -->            <key column="cid"></key>            <one-to-many class="cn.itcast.hiberate.sh.domain.Student"/>        </set>    </class></hibernate-mapping>

<?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"><hibernate-configuration>    <!--         一个session-factory只能连接一个数据库    --><session-factory>    <!--         数据库的用户名    -->    <property name="connection.username">root</property>    <!--         密码    -->    <property name="connection.password">root</property>    <!--         url    -->    <property name="connection.url">        jdbc:mysql://localhost:3306/itcast_sh_hibernate    </property>    <!--         作用：根据持久化类和映射文件生成表        validate        create-drop        create        update    -->    <property name="hbm2ddl.auto">update</property>    <!--         显示hibernate内部生成的sql语句    -->    <property name="show_sql">true</property>    <mapping resource="cn/itcast/hiberate/sh/domain/Classes.hbm.xml" />    <mapping resource="cn/itcast/hiberate/sh/domain/Student.hbm.xml" /></session-factory></hibernate-configuration>

package cn.itcast.hibernate.sh.utils;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.junit.Before;public class HibernateUtils {    public static SessionFactory sessionFactory;    public static String url;    // 需要在加载的时候就进行配置    @Before    public void init(){        // 创建 Configuration 对象        Configuration configuration = new Configuration();        // 加载配置文件        configuration.configure(url);        sessionFactory = configuration.buildSessionFactory();    }}

package cn.itcast.hibernate.sh.test;import java.util.HashSet;import java.util.Set;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import cn.itcast.hiberate.sh.domain.Classes;import cn.itcast.hiberate.sh.domain.Student;import cn.itcast.hibernate.sh.utils.HibernateUtils;public class TestOneToMany extends HibernateUtils{    static{        url="/hibernate.cfg.xml";    }    // 建表    @Test    public void  testCreateTable(){            }    // 创建一个班级    /**     * Hibernate: select max(cid) from Classes       Hibernate: insert into Classes (cname, description, cid) values (?, ?, ?)     */    @Test    public void save_classes(){        Session session = sessionFactory.openSession();        // 除了查询之外的操作都需要使用事务        Transaction transaction = session.beginTransaction();        Classes classes = new Classes();        classes.setCname("峡谷1");        classes.setDescription("召唤师峡谷");        session.save(classes);     // 将临时状态的对象转换成持久化状态        transaction.commit();        session.close();    }    // 创建一个学生    /**     * Hibernate: select max(sid) from Student       Hibernate: insert into Student (sname, description, sid) values (?, ?, ?)     */    @Test    public void save_student(){        // session 的实质可以看为一个数据库连接        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Student student = new Student();        student.setSname("黑铁");        student.setDescription("菜");        session.save(student);        transaction.commit();        session.close();    }    // 创建一个班级的时候同事创建一个学生,级联同时维护关系所以student表的外键也有值了    /**     *  Hibernate: select max(cid) from Classes        Hibernate: select max(sid) from Student        Hibernate: insert into Classes (cname, description, cid) values (?, ?, ?)        Hibernate: insert into Student (sname, description, sid) values (?, ?, ?)        Hibernate: update Student set cid=? where sid=?     */    @Test    public void saveClasses_cacade_saveStudent(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = new Classes();        classes.setCname("峡谷2");        classes.setDescription("召唤师峡谷2");        Student student = new Student();        student.setSname("白银呢");        student.setDescription("还是菜");        Set<Student> students = new HashSet<Student>();        students.add(student);        classes.setStudents(students);        session.save(classes);        transaction.commit();        session.close();    }    // 存在一个班级，新建一个学生    /**     *  Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_,      *  classes0_.description as descript3_0_0_ from Classes classes0_ where classes0_.cid=?        Hibernate: select students0_.cid as cid0_1_, students0_.sid as sid1_,         students0_.sid as sid1_0_, students0_.sname as sname1_0_, students0_.description as descript3_1_0_ from Student students0_ where students0_.cid=?        Hibernate: select max(sid) from Student        Hibernate: insert into Student (sname, description, sid) values (?, ?, ?)        Hibernate: update Student set cid=? where sid=?     */    @Test    public void test_classes_saveStudent(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = (Classes) session.get(Classes.class, 4L);        Student student = new Student();        student.setSname("白白");        student.setDescription("有点菜");        // classes 是持久化状态 可以直接添加        classes.getStudents().add(student);        session.save(classes);        transaction.commit();        session.close();    }    // 存在一个学生，新建一个班级    /**     *  Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_,      *  student0_.description as descript3_1_0_ from Student student0_ where student0_.sid=?        Hibernate: select max(cid) from Classes        Hibernate: insert into Classes (cname, description, cid) values (?, ?, ?)        Hibernate: update Student set cid=? where sid=?     */    @Test    public void test_student_saveClasses(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Student student = (Student) session.get(Student.class, 1L);        Classes classes = new Classes();        classes.setCname("峡谷3");        classes.setDescription("召唤师峡谷3");        Set<Student> students = new HashSet<Student>();        students.add(student);        classes.setStudents(students);        // 临时状态的 classes 需要 save        session.save(classes);        transaction.commit();        session.close();    }    // 存在一个 班级和学生 ，将其建立连接    /**     *  Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_,      *  classes0_.description as descript3_0_0_ from Classes classes0_ where classes0_.cid=?        Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_,         student0_.description as descript3_1_0_ from Student student0_ where student0_.sid=?        Hibernate: select students0_.cid as cid0_1_, students0_.sid as sid1_, students0_.sid as sid1_0_,         students0_.sname as sname1_0_, students0_.description as descript3_1_0_          from Student students0_ where students0_.cid=?        Hibernate: update Student set cid=? where sid=?     */    @Test    public void updateClasses_cascade_updateStudent(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = (Classes) session.get(Classes.class, 2L);        Student student = (Student) session.get(Student.class, 5L);        classes.getStudents().add(student);        transaction.commit();        session.close();    }    // 把一个学生从一个班级解除关系    /**     *  Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_,      *  classes0_.description as descript3_0_0_ from Classes classes0_ where classes0_.cid=?        Hibernate: select students0_.cid as cid0_1_, students0_.sid as sid1_,         students0_.sid as sid1_0_, students0_.sname as sname1_0_, students0_.description         as descript3_1_0_ from Student students0_ where students0_.cid=?        Hibernate: update Student set cid=null where cid=? and sid=?     */    @Test    public void test_release(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = (Classes) session.get(Classes.class, 2L);        Set<Student> students = classes.getStudents();        for(Student s : students){            if(s.getSid() == 5){                students.remove(s);            }        }        // 解除了学生5的关系        transaction.commit();        session.close();    }    // 解除一个班级下面的一些学生的关系    @Test    public void test_releaseR(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = (Classes) session.get(Classes.class, 2L);        Set<Student> students = classes.getStudents();        for(Student s : students){                            students.remove(s);                    }        // 解除了班级2下面的关系        transaction.commit();        session.close();    }    // 删除学生    /**     * Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_,      * student0_.description as descript3_1_0_ from Student student0_ where student0_.sid=?       Hibernate: delete from Student where sid=?     */    @Test    public void testDelete(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Student student = (Student) session.get(Student.class, 5L);        session.delete(student);        transaction.commit();        session.close();    }    // 删除班级    /**     *  Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_, classes0_.description as descript3_0_0_ from Classes classes0_ where classes0_.cid=?        Hibernate: update Student set cid=null where cid=?        Hibernate: delete from Classes where cid=?        删除班级的同时级联删除了 学生表中相应的外键     */    @Test    public void test_deleteClasses(){        Session session = sessionFactory.openSession();        Transaction transaction = session.beginTransaction();        Classes classes = (Classes) session.get(Classes.class, 5L);        session.delete(classes);        transaction.commit();        session.close();    }}