Annotation使用两个foreign key做联合主键

Annotation使用两个foreign key做联合主键

1、 数据库里面的表结构
学生：（Id ， Name）
课程：（Id ， Name）
选课表：（Student_ID ， Course_ID ， Score）
2、 Student类

package com.edu.hpu;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.JoinTable;import javax.persistence.ManyToMany;import javax.persistence.Table;@Entity@Table(name="_student")public class Student {private int id;private String name;private Set<Course> courses  = new HashSet<Course>();@Id@GeneratedValuepublic 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;}@ManyToMany@JoinTable(name="_score" ,joinColumns=@JoinColumn(name="student_ID"),inverseJoinColumns=@JoinColumn(name="course_ID"))public Set<Course> getCourses() {return courses;}public void setCourses(Set<Course> courses) {this.courses = courses;}}

3、 Course类

package com.edu.hpu;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="_course")public class Course {private int id;private String name;@Id@GeneratedValuepublic 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;}}

4、 Score类以及PK类

package com.edu.hpu;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="_score")public class Score {private int score;private PK pk;public int getScore() {return score;}public void setScore(int score) {this.score = score;}@Idpublic PK getPk() {return pk;}public void setPk(PK pk) {this.pk = pk;}}

package com.edu.hpu;import java.io.Serializable;import javax.persistence.Embeddable;import javax.persistence.JoinColumn;import javax.persistence.ManyToOne;@Embeddablepublic class PK implements Serializable {private Student student;private Course course;@ManyToOne@JoinColumn(name="student_ID")public Student getStudent() {return student;}public void setStudent(Student student) {this.student = student;}@ManyToOne@JoinColumn(name="course_ID")public Course getCourse() {return course;}public void setCourse(Course course) {this.course = course;}@Overridepublic boolean equals(Object obj) {if(obj instanceof PK) {PK pk = (PK)obj;if(pk.getCourse().getId() == this.getCourse().getId() && pk.getStudent().getId() == this.getStudent().getId()) {return true;}}return false;}@Overridepublic int hashCode() {return student.getName().hashCode() + course.getName().hashCode();}}

5、 测试生成表类（Junit）

package com.edu.hpu;import java.util.Set;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.hibernate.service.ServiceRegistryBuilder;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;public class TestWork {private static SessionFactory sf = null;@BeforeClasspublic static void beforeClass() {Configuration conf = new Configuration().configure();ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(conf.getProperties()).buildServiceRegistry();sf = conf.buildSessionFactory(sr);}@Testpublic void testExport() {new SchemaExport(new Configuration().configure()).create(true , true);}@Testpublic void testSave() {Course co = new Course();co.setName("C++");Student st = new Student();st.setName("qinrui");st.setId(1);Score sc = new Score();PK pk = new PK();pk.setCourse(co);pk.setStudent(st);sc.setPk(pk);sc.setScore(98);Session session = sf.getCurrentSession();session.beginTransaction();session.save(co);session.save(st);session.save(sc);session.getTransaction().commit();}@Testpublic void testGet() {Session session = sf.getCurrentSession();session.beginTransaction();Student st = (Student)session.get(Student.class, 6);Set<Course> courses = st.getCourses();for(Course cou : courses) {System.out.println(cou.getName());}session.getTransaction().commit();}@AfterClasspublic static void afterClass() {sf.close();}}

6、 Hiberante.cfg.xml配置

<?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>        <!-- Database connection settings -->        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>        <property name="connection.username">root</property>        <property name="connection.password">mima</property>        <!-- JDBC connection pool (use the built-in) -->        <property name="connection.pool_size">1</property>        <!-- SQL dialect -->        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>        <!-- Enable Hibernate's automatic session context management -->        <property name="current_session_context_class">thread</property>        <!-- Disable the second-level cache  -->        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>        <!-- Echo all executed SQL to stdout -->        <property name="show_sql">true</property>                <property name="format_sql">true</property>        <!-- Drop and re-create the database schema on startup -->        <!--<property name="hbm2ddl.auto">update</property>-->        <!--<mapping resource="org/hibernate/tutorial/domain/Event.hbm.xml"/>-->                <!--<mapping resource="com/edu/hpu/Husband.hbm.xml" />-->        <!--        <mapping resource="com/edu/hpu/Teacher.hbm.xml" />        <mapping resource="com/edu/hpu/Student.hbm.xml" />        -->        <mapping class="com.edu.hpu.Student" />        <mapping class="com.edu.hpu.Course" />        <mapping class="com.edu.hpu.Score" />                    </session-factory></hibernate-configuration>

7、 生成的建表语句

create table _course (        id integer not null auto_increment,        name varchar(255),        primary key (id)    )    create table _score (        score integer not null,        course_ID integer,        student_ID integer,        primary key (student_ID, course_ID)    )    create table _student (        id integer not null auto_increment,        name varchar(255),        primary key (id)    )    alter table _score         add index FKA89FA193A2A75DE0 (course_ID),         add constraint FKA89FA193A2A75DE0         foreign key (course_ID)         references _course (id)    alter table _score         add index FKA89FA19337241E94 (student_ID),         add constraint FKA89FA19337241E94         foreign key (student_ID)         references _student (id)