hibernate多对多关系

package com.manytomany;import java.util.HashSet;import java.util.Set;public class Student { ???private Long id; ???private String name; ???private Set<Teacher> teachers = new HashSet<Teacher>(); // 关联的老师们 ???public Long getId() { ???????return id; ???} ???public void setId(Long id) { ???????this.id = id; ???} ???public String getName() { ???????return name; ???} ???public void setName(String name) { ???????this.name = name; ???} ???public Set<Teacher> getTeachers() { ???????return teachers; ???} ???public void setTeachers(Set<Teacher> teachers) { ???????this.teachers = teachers; ???} ???@Override ???public String toString() { ???????return "[Student: id=" + id + ", name=" + name + "]"; ???}}

package com.manytomany;import java.util.HashSet;import java.util.Set;public class Teacher { ???private Long id; ???private String name; ???private Set<Student> students = new HashSet<Student>(); // 关联的学生们 ???public Long getId() { ???????return id; ???} ???public void setId(Long id) { ???????this.id = id; ???} ???public String getName() { ???????return name; ???} ???public void setName(String name) { ???????this.name = name; ???} ???public Set<Student> getStudents() { ???????return students; ???} ???public void setStudents(Set<Student> students) { ???????this.students = students; ???} ???@Override ???public String toString() { ???????return "[Teacher: id=" + id + ", name=" + name + "]"; ???}}

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ???????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???????"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.manytomany"> ???<class name="Student" table="t_student"> ???????<id name="id"> ???????????<generator class="native"></generator> ????????</id> ???????<property name="name" /> ???????<!-- ????????????teachers属性，Set集合，表达的是本类与Teacher的多对多的关系 ????????????table属性：中间表（集合表） ???????????key子元素：集合外键（引用当前表主键的那个外键） ???????--> ???????<set name="teachers" table="teacher_student" inverse="false"> ???????????<key column="studentId"></key> ???????????<many-to-many class="Teacher" column="teacherId"></many-to-many> ???????</set> ???</class></hibernate-mapping>

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ???????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???????"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.manytomany"> ???<class name="Teacher" table="teacher"> ???????<id name="id"> ???????????<generator class="native"></generator> ????????</id> ???????<property name="name" type="string" column="name" /> ???????<!-- students属性，Set集合，表达的是本类与Student的多对多的关系 ?--> ???????<set name="students" table="teacher_student" inverse="true"> ???????????<key column="teacherId"></key> ???????????<many-to-many class="Student" column="studentId"></many-to-many> ???????</set> ???</class></hibernate-mapping>

package com.manytomany.test;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.InputStream;import java.util.EnumSet;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.Metadata;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.junit.Test;import com.hello.Account;import com.hello.User;import com.manytomany.Student;import com.manytomany.Teacher;public class HelloTest { ???private static SessionFactory sessionFactory; ???static { ???????sessionFactory = new Configuration() ???????.configure() // 读取配置文件 ???????.buildSessionFactory(); ???} ???// 根据配置生成表结构 ???@Test ???public void test() { ???????//hibernate 5.0 ???????Configuration conf = new Configuration().configure();//1、读取配置文件 ???????StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build(); ???????Metadata metadata = new MetadataSources(serviceRegistry).buildMetadata(); ???} ???@Test ???public void hello(){ ???????Session session=sessionFactory.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//================================================== ???????Student student1 = new Student(); ???????student1.setName("王同学"); ???????Student student2 = new Student(); ???????student2.setName("李同学"); ???????Teacher teacher1 = new Teacher(); ???????teacher1.setName("赵老师"); ???????Teacher teacher2 = new Teacher(); ???????teacher2.setName("蔡老师"); ???????// 关联起来 ???????student1.getTeachers().add(teacher1); ???????student1.getTeachers().add(teacher2); ???????student2.getTeachers().add(teacher1); ???????student2.getTeachers().add(teacher2); ???????teacher1.getStudents().add(student1); ???????teacher1.getStudents().add(student2); ???????teacher2.getStudents().add(student1); ???????teacher2.getStudents().add(student2); ???????// 保存 ???????session.save(student1); ???????session.save(student2); ???????session.save(teacher1); ???????session.save(teacher2); ???????//================================================== ???????tx.commit(); ???} ???// 解除关联关系 ???@Test ???public void testRemoveRelation() { ???????Session session = sessionFactory.openSession(); ???????session.beginTransaction(); ???????// ------------------------------------------- ???????// 如果inverse=false就可以解除，如果为true就不可以解除（删除中间表中的记录） ???????// ???????Teacher teacher = (Teacher) session.get(Teacher.class, 3L); ???????// ???????teacher.getStudents().clear(); ???????Student student=session.get(Student.class, 4l); ???????student.getTeachers().clear(); ???????// ------------------------------------------- ???????session.getTransaction().commit(); ???????session.close(); ???} ???// 删除对象，对关联对象的影响 ???@Test ???public void testDelete() { ???????Session session = sessionFactory.openSession(); ???????session.beginTransaction(); ???????// ------------------------------------------- ???????// 删除老师方 ???????// a，如果没有关联的对方：能删除 ???????// b，如果有关联的对方且inverse=false，由于可以维护关联关系，它就会先删除关联关系，再删除自己。 ???????// c，如果有关联的对方且inverse=true，由于不能维护关联关系，所以会直接执行删除自己，就会有异常// ???????Teacher teacher = (Teacher) session.get(Teacher.class, 5L);// ???????session.delete(teacher); ???????Student student=session.get(Student.class, 6l); ???????session.delete(student); ???????// ------------------------------------------- ???????session.getTransaction().commit(); ???????session.close(); ???} ???@Test ???public void testGet(){ ???????Session session=sessionFactory.openSession(); ???}}

删除打印sql语句Hibernate: ????select ???????student0_.id as id1_1_0_, ???????student0_.name as name2_1_0_ ????from ???????t_student student0_ ????where ???????student0_.id=?Hibernate: ????delete ????from ???????teacher_student ????where ???????studentId=?Hibernate: ????delete ????from ???????t_student ????where ???????id=?