Hibernate多对多单向关联(一个many-to-many)

一个学生可以有多个老师，一个老师也可以有多个学生，所以老师和学生之间的关系就是多对多的关系，这样就需要建立一个中间的关联表来存储关联信息。

-- Create table
create table TEACHER
(
ID NUMBER(4) not null,
NAME VARCHAR2(100),
SOURCENAME VARCHAR2(100)
)

-- Create table
create table STUDENT
(
ID NUMBER(4) not null,
NAME VARCHAR2(100),
AGE NUMBER(4),
SEX VARCHAR2(100)
)

-- Create table
create table STUTEA
(
STUDENT_ID NUMBER(4) not null,
TEACHER_ID NUMBER(4) not null
)

package com.pojo; public class Student implements java.io.Serializable { private Long id; private String name; private Long age; private String sex; public Student() { } public Long getId() { return this.id; } public void setId(Long id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public Long getAge() { return this.age; } public void setAge(Long age) { this.age = age; } public String getSex() { return this.sex; } public void setSex(String sex) { this.sex = sex; } }

package com.pojo; import java.util.HashSet; import java.util.Set; public class Teacher implements java.io.Serializable { private static final long serialVersionUID = -7640561034271065452L; private Long id; private String name; private String sourcename; //多对多单向关联 private Set<Student> students = new HashSet<Student>() ; public Teacher() { } public Long getId() { return this.id; } public void setId(Long id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public String getSourcename() { return this.sourcename; } public void setSourcename(String sourcename) { this.sourcename = sourcename; } public Set<Student> getStudents() { return students; } public void setStudents(Set<Student> students) { this.students = students; } }

<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Mapping file autogenerated by MyEclipse Persistence Tools --> <hibernate-mapping> <class name="com.pojo.Teacher" table="TEACHER" schema="ZM"> <id name="id" type="java.lang.Long"> <column name="ID" precision="4" scale="0" /> <generator class="increment" /> </id> <property name="name" type="java.lang.String"> <column name="NAME" length="100" /> </property> <property name="sourcename" type="java.lang.String"> <column name="SOURCENAME" length="100" /> </property> <!-- 多对多单向关联,table标识关联表，key里面column属性代表该类（Teacher）在关联表里面的键是teacher_id many-to-many 里面class属性是set里面的类型，后面的column是指该类在关联表里面的外键 outer-join="true" 外连接 cascade="save-update" 级联操作 --> <set name="students" table="stutea" outer-join="true" cascade="save-update"> <key column="teacher_id"></key> <many-to-many class="com.pojo.Student" column="student_id"/> </set> </class> </hibernate-mapping>

测试类：

package com.test; import java.util.HashSet; import java.util.Set; import org.hibernate.Session; import com.pojo.Card; import com.pojo.Person; import com.pojo.Student; import com.pojo.Teacher; import com.util.HibernateManager; public class Test4 { public static void main(String[] args) { Test4.addPerson(); } public static void addPerson() { Session session = HibernateManager.openSession(); Student s1 = new Student(); Student s2 = new Student(); s1.setName("张三"); s1.setAge(new Long(20)); s1.setSex("男"); s2.setName("小丽"); s2.setAge(new Long(20)); s2.setSex("女"); Set<Student> set = new HashSet<Student>(); set.add(s1); set.add(s2); Teacher t = new Teacher(); t.setName("王老师"); t.setSourcename("语文"); t.setStudents(set); try { //只需要save teacher,因为设置了cascade="save-update" 级联操作 session.save(t); HibernateManager.closeSession(); } catch (Exception e) { e.printStackTrace(); HibernateManager.rollbackTransaction(); } } }