hibernate--多对多单向（双向）关联

Teacher和Student来说明：

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Annotation注解：

teacher->student

Teacher.java:

package com.bean; import java.util.HashSet; import java.util.Set; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinColumns; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; @Entity public class Teacher { private int id; private String name; private Set<Student> students = new HashSet<Student>(); @ManyToMany @JoinTable(name="t_s", joinColumns=@JoinColumn(name="TeacherID"), inverseJoinColumns=@JoinColumn(name="stuendID") ) public Set<Student> getStudents() { return students; } public void setStudents(Set<Student> students) { this.students = students; } @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

Student.java:

package com.bean; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; @Entity public class Student { private int id; private String name; @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

cfg.xml配置文件： <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/user</property> <property name="connection.username">root</property> <property name="connection.password">root</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="show_sql">true</property> <property name="hbm2ddl.auto">update</property> <property name="show_sql">true</property> <property name="format_sql">true</property> <property name="current_session_context_class">thread</property> <mapping class="com.bean.Student"/> <mapping class="com.bean.Teacher"/> </session-factory> </hibernate-configuration>

XML配置:

Student.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name = "com.bean.Student" table = "student" > <id name = "id" column="id"> <generator class="native"/> </id> <property name="name" /> </class> </hibernate-mapping> Teacher.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name = "com.bean.Teacher" table = "teacher" > <id name = "id" column="id"> <generator class="native"/> </id> <property name="name" /> <set name="students" table="t_s"> <key column="teacher_Id"></key> <many-to-many class="com.bean.Student" column="student_Id"/> </set> </class> </hibernate-mapping> cfg.xml中修改映射配置 <mapping resource="com/bean/Student.hbm.xml"/> <mapping resource="com/bean/Teacher.hbm.xml"/>

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多对多双向关联：

1、xml配置： Student.hbm.xml中添加配置即可：

<set name="teachers" table="t_s"> <key column="student_Id"></key> <many-to-many class="com.bean.Teacher" column="teacher_Id"/> </set>

2、Annotation配置：

在Student.java中添加：

@ManyToMany(mappedBy="students") public Set<Teacher> getTeachers() { return teachers; } public void setTeachers(Set<Teacher> teachers) { this.teachers = teachers; }