Hibernate中map的研究：多对多

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Teacher.java

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package blog.hibernate.domain;import java.util.HashMap;import java.util.List;import java.util.Map;public class Teacher {    private int id;    private String name;    private String course;    private Map<String, Student> students = new HashMap<String, Student>();    public Map<String, Student> getStudents() {        return students;    }    public void setStudents(Map<String, Student> students) {        this.students = students;    }        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;    }         public String getCourse() {        return course;    }    public void setCourse(String course) {        this.course = course;    }    @Override    public String toString() {        return "Teacher{" + "id=" + id + ", name=" + name + ", course=" + course + '}';    }}

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Teacher.hbm.xml

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<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="blog.hibernate.domain"><class name="Teacher" table="teachers"><id name="id" column="teacher_id"><generator class="native"></generator></id><property name="name" column="teacher_name"></property><property name="course"></property>                  <map name="students" table="teacher_student" inverse="true">                    <key column="teacher_id" />                    <index column="Course" type="string"/>                    <many-to-many class="Student" column="student_id"/>                  </map></class></hibernate-mapping>

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Student.java

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package blog.hibernate.domain;import java.util.HashMap;import java.util.List;import java.util.Map;public class Student {    private int id;    private String name;    private Map<String, Teacher> teachers = new HashMap<String, Teacher>();    public Map<String, Teacher> getTeachers() {        return teachers;    }    public void setTeachers(Map<String, Teacher> teachers) {        this.teachers = teachers;    }        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;    }    @Override    public String toString() {        return "Student{" + "id=" + id + ", name=" + name + '}';    }}

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Student.hbm.xml

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<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="blog.hibernate.domain"><class name="Student" table="students"><id name="id" column="student_id"><generator class="native"></generator></id><property name="name" column="student_name"></property>                                  <map name="teachers" table="teacher_student">                       <key column="student_id"/>                       <index column="Course" type="string"/>                       <many-to-many class="Teacher" column="teacher_id"/>                 </map></class></hibernate-mapping>

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hibernate.cfg.xml

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<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC    "-//Hibernate/Hibernate Configuration DTD//EN"    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration>    <session-factory>        <property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver</property>        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate</property><!-- ///表示连接本机的数据库//localhost:3306 -->        <property name="hibernate.connection.username">root</property>        <property name="hibernate.connection.password">1234</property>        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>           <property name="hibernate.hbm2ddl.auto">create</property>        <property name="hibernate.show_sql">true</property>                        <mapping resource="blog/hibernate/domain/Student.hbm.xml"/>        <mapping resource="blog/hibernate/domain/Teacher.hbm.xml"/>     </session-factory></hibernate-configuration>

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junit test

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package juint.test;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.BeforeClass;import org.junit.Test;import blog.hibernate.HibernateUtil;import blog.hibernate.domain.Student;import blog.hibernate.domain.Teacher;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.logging.Level;import java.util.logging.Logger;public class Many2Many {    @BeforeClass    public static void setUpBeforeClass() throws Exception {    }    @Test    public void test() {        map_add();    }    public void map_add() {        Teacher t1 = new Teacher();        t1.setName("t1");        t1.setCourse("Math");        Teacher t2 = new Teacher();        t2.setName("t2");        t2.setCourse("English");        Student s1 = new Student();        s1.setName("s1");        Student s2 = new Student();        s2.setName("s2");        /**         * 第一种方法         */        Map<String, Teacher> teachers = new HashMap<String, Teacher>();        teachers.put("Math", t1);        teachers.put("English", t2);        s1.setTeachers(teachers);        s2.setTeachers(teachers);        /**         * 第二种方法         *///                s1.getTeachers().put("Math", t1);//                s1.getTeachers().put("English", t2);//                //                s2.getTeachers().put("Math", t1);//                s2.getTeachers().put("English", t2);        Session session = null;        Transaction tx = null;        try {            session = HibernateUtil.getSession();            tx = session.beginTransaction();            session.save(s1);            session.save(s2);            session.save(t1);            session.save(t2);            tx.commit();        } catch (Exception e) {            Logger.getLogger(Many2Many.class.getName()).log(Level.SEVERE, null, e);            if (tx != null) {                tx.rollback();            }        } finally {            if (session != null) {                session.close();            }        }    }}