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 ,student
2.创建Zlass和Student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;
 }
 
}

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 class="assigned"/>
    </id>
    <property name="className" column="class_name" type="string" length="200"/>
    
    <set name="students" inverse="false" cascade="all">
      <key column="class_id"/><1--class_id 是学生表中的班级id-->
      <one-to-many class="Student"/>
    </set>
 </class>
</hibernate-mapping>

Student.hbm.xml

<hibernate-mapping package="com.softWork.school">
 <class name="Student" table="student">
    <id name="studentId" column="student_id" type="string" length="20">
      <generator class="assigned"/>
    </id>
    <property name="name" type="string" length="20"/>
    <component name="address" class="Address">
      <property name="state" 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 class="Event"></one-to-many>
    </set>
    
    <set name="lessons" table="student_lesson">
      <key column="student_id"/>
      <many-to-many class="Lesson" column="lesson_id" />
    </set>
    <many-to-one name="zlass" column="class_id" class="Zlass"/>
 </class>
</hibernate-mapping>

对班级和学生进行维护

// 使用级连操作数据
//新增班级
Zlass zlass = new Zlass();
zlass.setId("971002");
zlass.setClassName("机制97-1班");
session.saveOrUpdate(zlass);
//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);
//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);
//被动操作
Student student = (Student)session.load(Student.class,"002");
session.delete(student);
//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());
}

注意：
inverse属性默认是false，若为false，则对应的属性由自己控制，若为true，则关联
由对方控制。
inverse属性只能在set、list、map等几个标签中设置。
如果需要从多方引导到一方，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”的表示关系维护的权力交给对方。
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inverse=“FALSE”的情况下的结果。

例子：http://www.cnblogs.com/otomedaybreak/archive/2012/01/17/2324772.html