hibernate的list映射和map映射

List映射

Grade类

public class Grade {private int id;private String name;private List<Student> students=new ArrayList<Student>();//省略get/set方法}

Student类

public class Student {private int id;private String name;private int age;//省略get/set方法}

Grade.hbm.xml配置文件

<hibernate-mapping package="com.test.pojo"><class name="Grade"><id name="id"><generator class="native"></generator></id><property name="name" /><list name="students"> <key column="grade_id" not-null="true"></key> <!-- 在多的一端产生一列用来表示顺序，如果不指明列名默认为idx      值由hibernate来维护  --> <list-index column="sort"/> <one-to-many class="Student"/></list></class></hibernate-mapping>

Student.hbm.xml配置文件

<hibernate-mapping package="com.test.pojo"><class name="Student"><id name="id"><generator class="native"></generator></id><property name="name" /><property name="age"/></class></hibernate-mapping>

测试类

public class HibernateTest {@Testpublic void testCreateDB(){Configuration cfg=new Configuration().configure();SchemaExport se=new SchemaExport(cfg);//第一个参数表示是否生成ddl脚本，第二个参数表示是否执行到数据库中se.create(true, true);}/** * 保存数据 */@Testpublic void save(){Session session=null;Transaction tx=null;try{session=HibernateUtil.getSession();tx=session.beginTransaction();Grade grade=new Grade();grade.setName("大一");Student stu=new Student();stu.setName("张三");stu.setAge(20);Student stu1=new Student();stu1.setName("李四");stu1.setAge(20);Student stu2=new Student();stu2.setName("王五");stu2.setAge(20);grade.getStudents().add(stu);grade.getStudents().add(stu1);grade.getStudents().add(stu2);session.save(grade);session.save(stu);session.save(stu1);session.save(stu2);tx.commit();}catch(Exception e){if(tx!=null)tx.rollback();e.printStackTrace();}finally{HibernateUtil.closeSession();}}@Testpublic void testGet(){Session session=null;Transaction tx=null;try{session=HibernateUtil.getSession();tx=session.beginTransaction();//取数据Grade grade=(Grade) session.get(Grade.class,1);System.out.println("grade_name:"+grade.getName());Iterator<Student> it=grade.getStudents().iterator();while(it.hasNext()){Student student=(Student)it.next();System.out.println("student_name:"+student.getName());}tx.commit();}catch(Exception e){tx.rollback();e.printStackTrace();}finally{HibernateUtil.closeSession();}}}

Map映射

只展示与List映射不同之处

Grade类

public class Grade {private int id;private String name;private Map<String,Student> students=new HashMap<String,Student>();//省略get/set方法}

Grade.hbm.xml配置文件

<hibernate-mapping package="com.test.pojo"><class name="Grade"><id name="id"><generator class="native"></generator></id><property name="name" /><map name="students" cascade="all"><!-- key表示外键 --> <key column="grade_id" /> <!-- map-key是映射为map集合时，对应key值，建议为唯一的 --> <map-key type="String" column="name"/> <one-to-many class="Student"/></map></class></hibernate-mapping>

测试类（保存数据和获取数据代码）

@Testpublic void save(){Session session=null;Transaction tx=null;try{session=HibernateUtil.getSession();tx=session.beginTransaction();Grade grade=new Grade();grade.setName("大一");Student stu=new Student();stu.setName("张三");stu.setAge(20);Student stu1=new Student();stu1.setName("李四");stu1.setAge(20);Student stu2=new Student();stu2.setName("王五");stu2.setAge(20);grade.getStudents().put(stu.getName(), stu);grade.getStudents().put(stu1.getName(), stu1);grade.getStudents().put(stu2.getName(), stu2);session.save(grade);session.save(stu);session.save(stu1);session.save(stu2);tx.commit();}catch(Exception e){if(tx!=null)tx.rollback();e.printStackTrace();}finally{HibernateUtil.closeSession();}}@Testpublic void testGet(){Session session=null;Transaction tx=null;try{session=HibernateUtil.getSession();tx=session.beginTransaction();//取数据Grade grade=(Grade) session.get(Grade.class,1);System.out.println("grade_name:"+grade.getName());Map<String,Student> map=grade.getStudents();System.out.println(map.get("张三").getAge());tx.commit();}catch(Exception e){tx.rollback();e.printStackTrace();}finally{HibernateUtil.closeSession();}}

所有代码实例结果在此不做展示，可自己运行查看。