HIBERNATE一对多配置实例
HIBERNATE一对多配置实例1．?环境：假定班级和学生是一对多的关系，班级是一，学生是多，对应表格分别是：zlass ,student2．?创建Zlass和Student对象//Zlass对象---------------------??? public class Zlass{??private String class_id;?private String class_name;?private java.util.Set students;??public void setId(String id){??? this.class_id = id;?}??public void setClassName(String className){??? this.class_name = className;?}??public void setStudents(java.util.Set students){??? this.students = students;?}??public String getId(){??? return class_id;?}??public String getClassName(){??? return class_name;?}??public java.util.Set getStudents(){??? return students;?}?}?//学生对象public class Student{?????? private String student_id;?????? private String name;?????? private Address address;?????? private java.util.Set events;?????? private java.util.Set lessons;?????? private Zlass zlass;?????? ?????? public Zlass getZlass(){????????????? return zlass;?????? }??????? public String getStudentId(){????????????? return student_id;?????? }?????? ?????? public String getName(){????????????? return name;?????? }?????? ?????? public Address getAddress(){????????????? return address;?????? }?????? ?????? public java.util.Set getEvents(){????????????? return events;?????? }?????? ?????? public java.util.Set getLessons(){????????????? return lessons;?????? }??????? public void setZlass(Zlass zlass){?????? ?????? this.zlass = zlass;?????? }?????? ?????? public void setStudentId(String studentId){?????? ?????? this.student_id = studentId;?????? }?????? ?????? public void setName(String name){?????? ?????? this.name = name;?????? }?????? ?????? public void setAddress(Address address){?????? ?????? this.address = address;?????? }?????? ?????? public void setEvents(java.util.Set events){?????? ?????? this.events =events;?????? }?????? ?????? public void setLessons(java.util.Set lessons){?????? ?????? this.lessons = lessons;?????? }?????? }??//配置文件//----------Zlass.hbm.xml---------------<hibernate-mapping package="com.softWork.school">?<class name="Zlass" table="class">??? <id name="id" column="id" type="string" length="20">????? <generator column="class_name" type="string" length="200"/>??? ??? <set name="students" inverse="false" cascade="all">????? <key column="class_id"/>????? <one-to-many table="student">??? <id name="studentId" column="student_id" type="string" length="20">????? <generator type="string" length="20"/>??? <component name="address" column="state" type="string"></property>????? <property name="city" column="city" type="string"></property>????? <property name="street" column="street" type="string"></property>??? </component>??? <set name="events" inverse="false" cascade="all">????? <key column="student_id"></key>????? <one-to-many table="student_lesson">????? <key column="student_id"/>????? <many-to-many column="lesson_id" />??? </set>??? <many-to-one name="zlass" column="class_id" class="Zlass"/>?</class></hibernate-mapping>?以上使用的是班级一端维护关系，并级连操作?3．?使用级连操作数据1）?新增班级?????? Zlass zlass = new Zlass();????? ?zlass.setId("971002");?????? zlass.setClassName("机制97-1班");session.saveOrUpdate(zlass);2）?为班级新增学生主动端操作：????? Zlass zlass = (Zlass)session.load(Zlass.class,"971002");????? Student student = new Student();????? student.setStudentId("005");????? student.setName("没名");????? zlass.getStudents().add(student);????? session.saveOrUpdate(zlass);被动端操作：????? Zlass zlass = (Zlass)session.load(Zlass.class,"971002");????? Student student = new Student();????? student.setStudentId("006");????? student.setName("006");????? student.setZlass(zlass);session.saveOrUpdate(student);3）?删除学生资料主动端操作：主动端除非删除自己，并设置了级连才能删除子对象，否则无法完成//-----以下代码将只删除两者之间的关系，即将学生的class_id设置为null-----Zlass zlass = (Zlass)session.load(Zlass.class,"971001");java.util.Iterator iterator = zlass.getStudents().iterator();????? if (iterator.hasNext())??????? zlass.getStudents().remove(iterator.next());????? session.saveOrUpdate(zlass);被动端操作：????????????? Student student = (Student)session.load(Student.class,"002");session.delete(student);4）?修改学生资料通过班级修改学生资料?Zlass zlass = (Zlass)session.load(Zlass.class,"971002");????? java.util.Iterator iterator = zlass.getStudents().iterator();????? if (iterator.hasNext()){?????? ?Student student?= (Student)iterator.next();??????? student.setName("名字已修改");????? }session.saveOrUpdate(zlass);?读取返回的Set型数据：java.util.Set set = student.getEvents();java.util.Iterator iterator = set.iterator();while(iterator.hasNext()){evt = (Event)iterator.next();System.out.println(evt.getContent());System.out.println(evt.getDate().toString());}?4．?注意：如果需要从多放引导到一方，需要在一方配置文件中设置inverse=”true”参数，以设定一方到多方的设定是逆向映射，对关联的逆向端所做的修改将不会被持久化。Inverse=”true”的表示两个实体的关系由对方去维护。5．?推荐配置，一般的将”一”这一端设置为inverse=”false”，cascade=”all” ，这样一般的操作只需要在”一”这一端操作,此适合于标志性一对多的情况，如销售单和销售明细如果是非标志性一对多，则一般的将inverse=”false”,cascade=”none”,这样关系永远在主动一端进行控制示范：假如A对B是一对多，当A中原来有B1，B2，B3，当A中的集合中只包含B1，B2时，那么B中B3的外码将被设置为NULL，这个是CASCADE=“FALSE”的情况下的结果