Hibernate中map的研究:多对多
***************
Teacher.java
***************
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 + '}'; } }
***************
Teacher.hbm.xml
***************
<?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>
***************
Student.java
***************
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 + '}'; } }
***************
Student.hbm.xml
***************
<?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>
***************
hibernate.cfg.xml
***************
<?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>
******************
junit test
*****************
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(); } } } }