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Hibernate 一对多双向关联Demo
以Classes[班级]和Student[学生]为例的Demo
//Classes.javapublic class Classes implements Serializable { private long cid; private String cname; private String cdesc; private Set<Student> students; //get和set }
//Student .javapublic class Student implements Serializable { private long sid; private String sname; private String sdesc; private Classes classes; //get和set}
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 <hibernate-mapping> 5 <class name="cn.test.testDoubl.Classes" > 6 <id name="cid" type="java.lang.Long" length="5"> 7 <column name="cid"></column> 8 <generator class="increment"></generator> 9 </id>10 <property name="cname" type="java.lang.String" length="20"></property>11 <property name="cdesc" type="java.lang.String" length="50"></property>12 <!-- 13 cascade指的是对象对对象的操作14 inverse指的是对象对关系的操作15 -->16 <set name="students" cascade="all">17 <key>18 <!-- 19 通过classes建立与student之间的联系20 -->21 <column name="cid"></column>22 </key>23 <one-to-many class="cn.test.testDoubl.Student"/>24 </set>25 </class>26 </hibernate-mapping>
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 <hibernate-mapping> 5 <class name="cn.test.testDoubl.Student"> 6 <id name="sid" type="java.lang.Long" length="5"> 7 <column name="sid"></column> 8 <generator class="increment"></generator> 9 </id>10 <property name="sname" type="java.lang.String" length="20"></property>11 <property name="sdesc" type="java.lang.String" length="50"></property>12 <!-- 13 多对一14 注意：在many-to-one中没有inverse属性15 对student表的修改本身就是维护外键16 -->17 <many-to-one name="classes" class="cn.test.testDoubl.Classes" cascade="all">18 <!-- 19 外键20 描述了通过student建立与classes之间的联系21 -->22 <column name="cid"></column>23 </many-to-one>24 </class>25 </hibernate-mapping>
总结：
当发生transaction.commit的时候，hibernate内部会检查所有的持久化对象 会对持久化对象做一个更新,因为classes是一个持久化状态的对象，所以hibernate 内部要对classes进行更新，因为在classes.hbm.xml文件中<set name="students" cascade="all" inverse="true"> 意味着在更新classes的时候，要级联操作student,而student是一个临时状态的对象 所以要对student进行保存，在保存student的时候，就把外键更新了。
1 package cn.test.testDoubl; 2 3 import java.util.HashSet; 4 import java.util.Set; 5 6 import org.hibernate.Session; 7 import org.hibernate.SessionFactory; 8 import org.hibernate.Transaction; 9 import org.hibernate.cfg.Configuration; 10 import org.junit.Test; 11 12 public class DoTestDoubl { 13 private static SessionFactory sessionFactory; 14 static{ 15 Configuration configuration=new Configuration(); 16 configuration.configure("cn/test/testDoubl/hibernate.cfg.xml"); 17 sessionFactory=configuration.buildSessionFactory(); 18 } 19 20 /** 21 * 1、保存班级 22 * 2、保存学生 23 * 3、保存班级的时候同时保存学生 24 * 4、保存班级的时候同时保存学生，并且建立班级和学生之间的关系 25 * 5、已经存在一个班级，新建一个学生，并且建立该学生和该班级之间的关系 26 * 6、已经存在一个学生，新建一个班级，并且建立该学生和该班级之间的关系 27 * 7、已经存在一个学生，已经存在一个班级，解除该学生和原来班级之间的关系，建立该学生和新班级之间的关系 28 * 8、已经存在一个学生，解除该学生和该学生所在班级之间的关系 29 * 9、解除该班级和所有的学生之间的关系，再重新建立该班级和一些新的学员之间的关系 30 * 10、解除该班级和所有的学生之间的关系 31 * 11、删除班级 32 * * 33 * * 解除该班级和所有的学生之间的关系 34 * * 删除该班级 35 * * 36 * 删除班级的同时删除学生 37 * 12、删除学生 38 * 同删除班级 39 */ 40 41 //3、保存班级的时候同时保存学生 42 /* 43 * Hibernate: select max(cid) from Classes 44 Hibernate: select max(sid) from Student 45 Hibernate: insert into Classes (cname, cdesc, cid) values (?, ?, ?) 46 Hibernate: insert into Student (sname, sdesc, cid, sid) values (?, ?, ?, ?) 47 Hibernate: update Student set cid=? where sid=? 48 */ 49 50 @Test 51 public void testSaveClassesandStudent(){ 52 53 Session session=sessionFactory.openSession(); 54 Transaction transaction=session.beginTransaction(); 55 Student student=new Student(); 56 student.setSname("1111"); 57 student.setSdesc("111111111111"); 58 59 Set<Student> set=new HashSet<Student>(); 60 set.add(student); 61 62 Classes classes=new Classes(); 63 classes.setCname("oo1"); 64 classes.setCdesc("我们都是No。1"); 65 66 classes.setStudents(set); 67 68 session.save(classes); 69 70 transaction.commit(); 71 session.close(); 72 73 } 74 75 76 //4、保存班级的时候同时保存学生，并且建立班级和学生之间的关系 77 /* 78 * Hibernate: select max(sid) from Student 79 Hibernate: select max(cid) from Classes 80 Hibernate: insert into Classes (cname, cdesc, cid) values (?, ?, ?) 81 Hibernate: insert into Student (sname, sdesc, cid, sid) values (?, ?, ?, ?) 82 */ 83 @Test 84 public void testSaveClassesandStudent2(){ 85 86 Session session=sessionFactory.openSession(); 87 Transaction transaction=session.beginTransaction(); 88 89 Student student=new Student(); 90 student.setSname("1111"); 91 student.setSdesc("111111111111"); 92 93 Classes classes=new Classes(); 94 classes.setCname("oo1"); 95 classes.setCdesc("我们都是No。1"); 96 97 student.setClasses(classes);//通过student来维护classes 98 //对student的增、删、改本身就是对外键的操作，所以这里不再发出update语句 99 //一对多，多的一方维护关系，效率比较高100 101 session.save(student);102 103 transaction.commit();104 session.close();105 106 }107 108 //5、已经存在一个班级，新建一个学生，并且建立该学生和该班级之间的关系109 /*110 * Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_, classes0_.cdesc as cdesc0_0_ from Classes classes0_ where classes0_.cid=?111 Hibernate: select max(sid) from Student112 Hibernate: insert into Student (sname, sdesc, cid, sid) values (?, ?, ?, ?)113 */114 @Test115 public void testSaveStudentToClasses(){116 Session session =sessionFactory.openSession();117 Transaction transaction=session.beginTransaction();118 119 Classes classes=(Classes) session.get(Classes.class, 1L);120 121 Student student=new Student();122 student.setSname("王尼玛");123 student.setSdesc("暴走漫画，就是劲爆");124 student.setClasses(classes);125 126 session.save(student);127 128 transaction.commit();129 session.close();130 }131 132 //6、已经存在一个学生，新建一个班级，并且建立该学生和该班级之间的关系133 /*134 * Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_, student0_.sdesc as sdesc1_0_, student0_.cid as cid1_0_ from Student student0_ where student0_.sid=?135 Hibernate: select max(cid) from Classes136 Hibernate: insert into Classes (cname, cdesc, cid) values (?, ?, ?)137 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?138 */139 @Test140 public void testSaveClassesToStudent(){141 Session session=sessionFactory.openSession();142 Transaction transaction=session.beginTransaction();143 144 Student student=(Student) session.get(Student.class, 1L);145 146 Classes classes=new Classes();147 classes.setCname("黑客集训");148 classes.setCdesc("里面都是牛人");149 150 student.setClasses(classes);151 152 session.save(classes);153 154 transaction.commit();155 session.close();156 }157 158 //7、已经存在一个学生，已经存在一个班级，解除该学生和原来班级之间的关系，建立该学生和新班级之间的关系159 /*160 * Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_, classes0_.cdesc as cdesc0_0_ from Classes classes0_ where classes0_.cid=?161 Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_, student0_.sdesc as sdesc1_0_, student0_.cid as cid1_0_ from Student student0_ where student0_.sid=?162 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?163 */164 @Test165 public void testToRebuild(){166 Session session=sessionFactory.openSession();167 Transaction transaction=session.beginTransaction();168 169 Classes classes=(Classes) session.get(Classes.class, 1L);170 Student student=(Student) session.get(Student.class, 1L);171 student.setClasses(classes);172 transaction.commit();173 session.close();174 }175 176 //8、已经存在一个学生，解除该学生和该学生所在班级之间的关系177 /*178 * Hibernate: select student0_.sid as sid1_0_, student0_.sname as sname1_0_, student0_.sdesc as sdesc1_0_, student0_.cid as cid1_0_ from Student student0_ where student0_.sid=?179 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?180 */181 @Test182 public void testToRomove(){183 Session session=sessionFactory.openSession();184 Transaction transaction=session.beginTransaction();185 186 Student student=(Student) session.get(Student.class, 1L);187 student.setClasses(null);188 189 transaction.commit();190 session.close();191 }192 193 //9、解除该班级和所有的学生之间的关系，再重新建立该班级和一些新的学员之间的关系194 /*195 * Hibernate: select classes0_.cid as cid0_0_, classes0_.cname as cname0_0_, classes0_.cdesc as cdesc0_0_ from Classes classes0_ where classes0_.cid=?196 Hibernate: select students0_.cid as cid0_1_, students0_.sid as sid1_, students0_.sid as sid1_0_, students0_.sname as sname1_0_, students0_.sdesc as sdesc1_0_, students0_.cid as cid1_0_ from Student students0_ where students0_.cid=?197 Hibernate: select max(sid) from Student198 Hibernate: insert into Student (sname, sdesc, cid, sid) values (?, ?, ?, ?)199 Hibernate: insert into Student (sname, sdesc, cid, sid) values (?, ?, ?, ?)200 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?201 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?202 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?203 Hibernate: update Student set sname=?, sdesc=?, cid=? where sid=?204 Hibernate: update Student set cid=? where sid=?205 Hibernate: update Student set cid=? where sid=?206 */207 @Test208 public void testremoveAndRebuild(){209 Session session=sessionFactory.openSession();210 Transaction transaction=session.beginTransaction();211 212 Classes classes=(Classes) session.get(Classes.class, 2L);213 Set<Student> students=classes.getStudents();214 for(Student student:students)215 {216 student.setClasses(null);217 }218 219 Student student=new Student();220 student.setSname("新建1");221 student.setSdesc("新建轩辕rtyuio");222 Student student2=new Student();223 student2.setSname("新建2");224 student2.setSdesc("新建轩sdfghyujikol;辕rtyuio");225 226 students.add(student);227 students.add(student2);228 229 transaction.commit();230 session.close();231 }232 233 //10、解除该班级和所有的学生之间的关系234 @Test235 public void testRemoveAllStudents(){236 Session session=sessionFactory.openSession();237 Transaction transaction=session.beginTransaction();238 239 Classes classes=(Classes) session.get(Classes.class, 2L);240 Set<Student> students= classes.getStudents();241 for(Student student:students){242 student.setClasses(null);243 }244 transaction.commit();245 session.close();246 }247 248 //11、删除班级249 //先解除关系，再删除班级250 @Test251 public void testDeleteClasses(){252 Session session=sessionFactory.openSession();253 Transaction transaction=session.beginTransaction();254 255 Classes classes=(Classes) session.get(Classes.class, 1L);256 Set<Student> set=classes.getStudents();257 for(Student student:set){258 student.setClasses(null);259 }260 session.delete(classes);261 transaction.commit();262 session.close();263 }264 265 //在删除班级的时候，同时删除整个班级的学生266 267 @Test268 public void testDeleteClasses2(){269 Session session=sessionFactory.openSession();270 Transaction transaction=session.beginTransaction();271 272 Classes classes=(Classes) session.get(Classes.class, 2L);273 Set<Student> set=classes.getStudents();274 for(Student student:set){275 student.setClasses(null);276 break;277 }278 //session.delete(classes);279 transaction.commit();280 session.close();281 }282 283 }
Hibernate 一对多双向关联Demo
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