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hibernate建表多对多建表
Student.java
1 package cn.itcast.hiberate.sh.domain; 2 3 import java.util.Set; 4 5 public class Student { 6 private Long sid; 7 private String sname; 8 private String description; 9 Set<Course> courses; 10 11 12 public Set<Course> getCourses() { 13 return courses; 14 } 15 public void setCourses(Set<Course> courses) { 16 this.courses = courses; 17 } 18 public Long getSid() { 19 return sid; 20 } 21 public void setSid(Long sid) { 22 this.sid = sid; 23 } 24 public Student(String sname, String description) { 25 super(); 26 this.sname = sname; 27 this.description = description; 28 } 29 public Student() { 30 // TODO Auto-generated constructor stub 31 } 32 public String getSname() { 33 return sname; 34 } 35 public void setSname(String sname) { 36 this.sname = sname; 37 } 38 public String getDescription() { 39 return description; 40 } 41 public void setDescription(String description) { 42 this.description = description; 43 } 44 45 }
Student.hbm.xml
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.itcast.hiberate.sh.domain.Student"> 6 <id name="sid" length="5"> 7 <generator class="increment"></generator> 8 </id> 9 <property name="sname" length="20"></property> 10 <property name="description" length="100"></property> 11 <!-- 12 table就是用来描述第三张表 13 key 用来描述外键，多对多的关系看对哪张表建立映射 14 此表是描述Student信息的，所以 key中 column写sid 15 16 many-to-many 中用于建立关系的所以 在第三张表中关系用cid建立 17 --> 18 <set name="courses" table="student_course"> 19 <key> 20 <column name="sid"></column> 21 </key> 22 <many-to-many class="cn.itcast.hiberate.sh.domain.Course" column="cid"> 23 </many-to-many > 24 </set> 25 </class> 26 </hibernate-mapping>
Course.java
1 package cn.itcast.hiberate.sh.domain; 2 3 import java.io.Serializable; 4 import java.util.Set; 5 6 public class Course implements Serializable { 7 private Long cid; 8 private String cname; 9 private String description; 10 private Set<Student> students; 11 public Long getCid() { 12 return cid; 13 } 14 public void setCid(Long cid) { 15 this.cid = cid; 16 } 17 public String getCname() { 18 return cname; 19 } 20 public void setCname(String cname) { 21 this.cname = cname; 22 } 23 public String getDescription() { 24 return description; 25 } 26 public void setDescription(String description) { 27 this.description = description; 28 } 29 public Set<Student> getStudents() { 30 return students; 31 } 32 public void setStudents(Set<Student> students) { 33 this.students = students; 34 } 35 36 }
Course.xml
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.itcast.hiberate.sh.domain.Course"> 6 <id name="cid" length="5" type="java.lang.Long"> 7 <generator class="increment"></generator> 8 </id> 9 <property name="cname" length="20" type="java.lang.String"></property> 10 11 <property name="description" length="100" type="java.lang.String"></property> 12 <!-- 13 set元素对应类中的set集合 14 通过set元素使classes表与student表建立关联 15 key是通过外键的形式让两张表建立关联，针对的是哪张表看哪个 16 one-to-many是通过类的形式让两个类建立关联 17 18 cascade 级联 19 save-update 20 1、当 保存班级的时候，对学生进行怎么样的操作 21 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 22 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 23 delete 24 all 25 inverse 维护关系 26 true 不维护关系 27 false 维护关系 28 default false 29 --> 30 <set name="students" table="student_course"> 31 <!-- 32 key是用来描述外键 哪张表就哪個外鍵 33 <many-to-many> 中的cid 描述类与类之间的关系 34 --> 35 <key> 36 <column name="cid"></column> 37 </key> 38 <many-to-many class="cn.itcast.hiberate.sh.domain.Student" column="sid"> 39 </many-to-many> 40 </set> 41 </class> 42 </hibernate-mapping>
hibernate.cfg.xml
1 <?xml version=‘1.0‘ encoding=‘utf-8‘?> 2 <!DOCTYPE hibernate-configuration PUBLIC 3 "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 4 "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 5 <hibernate-configuration> 6 <!-- 7 一个session-factory只能连接一个数据库 8 --> 9 <session-factory> 10 <!-- 11 数据库的用户名 12 --> 13 <property name="connection.username">root</property> 14 <!-- 15 密码 16 --> 17 <property name="connection.password">friends</property> 18 <!-- 19 url 20 --> 21 <property name="connection.url"> 22 jdbc:mysql://localhost:3306/itcast_sh_hibernate_manyTomany 23 </property> 24 <!-- 25 作用：根据持久化类和映射文件生成表 26 validate 27 create-drop 28 create 29 update 30 --> 31 <property name="hbm2ddl.auto">update</property> 32 <!-- 33 显示hibernate内部生成的sql语句 34 --> 35 36 <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> 37 <property name="show_sql">true</property> 38 <mapping resource="cn/itcast/hiberate/sh/domain/Course.hbm.xml" /> 39 <mapping resource="cn/itcast/hiberate/sh/domain/Student.hbm.xml" /> 40 41 </session-factory> 42 </hibernate-configuration>
test.java
1 package cn.itcast.hiberate.sh.test; 2 3 import org.hibernate.Session; 4 import org.hibernate.SessionFactory; 5 import org.hibernate.Transaction; 6 import org.hibernate.cfg.Configuration; 7 import org.junit.Test; 8 9 import cn.itcast.hibernate.sh.utils.HiberanteUtils; 10 11 public class CreateTable extends HiberanteUtils{ 12 13 @Test 14 public void createTable() 15 { 16 Configuration config=new Configuration(); 17 config.configure(); 18 // SessionFactory sessionFactory=config.buildSessionFactory(); 19 // Session session=sessionFactory.openSession(); 20 // Transaction transaction=session.beginTransaction(); 21 // 22 // 23 // transaction.commit(); 24 // session.close(); 25 } 26 }
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