Hibernate5-双向关联-多对多(n:n)
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1.创建项目,项目名称hibernatedemo15,目录结构如图所示
2.在项目中创建lib目录存储jar文件,目录结构如图所示
3.在src目录中创建实体类Course,包名(com.mycompany.demo.bean),如图所示
4.实体类Course的内容如下
package com.mycompany.demo.bean;
import java.util.Set;
public class Course {
private int cid;
private String name;
private Set<Student> students;
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
public Course() {
super();
}
public Course(String name) {
super();
this.name = name;
}
public int getCid() {
return cid;
}
public void setCid(int cid) {
this.cid = cid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}5.在src目录中创建实体类Course的映射文件Course.hbm.xml,包名(com.mycompany.demo.bean),如图所示
6.映射文件Course.hbm.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <!-- package:指定<class/>所在的包 --> <hibernate-mapping package="com.mycompany.demo.bean"> <!-- name:类名 table:表名 catalog:数据库名称,默认为hibernate.cfg.xml中配置的数据库名称 --> <class name="Course" table="course"> <meta attribute="class-description"> This class contains the course detail. </meta> <!-- name:属性名 colum:列名 --> <id name="cid" type="int" column="cid"> <!-- increment:hibernate维护主键值 identity:数据库自增长 sequence:序列 native:根据不同的数据库选择生成策略 uuid:通过UUID算法生成,实际使用较多 assigned:手工设置 --> <generator class="native"/> </id> <!-- length:字节长度 type:字段类型,支持java和hibernate类型 not-null:非空约束 unique:唯一性约束 --> <property name="name" column="name" /> <set name="students" table="student_course" cascade="save-update"> <key column="cid"/> <many-to-many class="Student" column="sid"></many-to-many> </set> </class> </hibernate-mapping>
7.在src目录中创建实体类Student,包名(com.mycompany.demo.bean),如图所示
8.实体类Student的内容如下
package com.mycompany.demo.bean;
import java.util.Set;
public class Student {
private int sid;
private String name;
private Set<Course> courses;
public Student() {
super();
}
public Student(String name) {
super();
this.name = name;
}
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Course> getCourses() {
return courses;
}
public void setCourses(Set<Course> courses) {
this.courses = courses;
}
}9.在src目录中创建实体类Student的映射文件Student.hbm.xml,包名(com.mycompany.demo.bean),如图所示
10.映射文件Student.hbm.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <!-- package:指定<class/>所在的包 --> <hibernate-mapping package="com.mycompany.demo.bean"> <!-- name:类名 table:表名 catalog:数据库名称,默认为hibernate.cfg.xml中配置的数据库名称 --> <class name="Student" table="student"> <meta attribute="class-description"> This class contains the student detail. </meta> <!-- name:属性名 colum:列名 --> <id name="sid" type="int" column="sid"> <!-- increment:hibernate维护主键值 identity:数据库自增长 sequence:序列 native:根据不同的数据库选择生成策略 uuid:通过UUID算法生成,实际使用较多 assigned:手工设置 --> <generator class="native"/> </id> <!-- length:字节长度 type:字段类型,支持java和hibernate类型 not-null:非空约束 unique:唯一性约束 --> <property name="name" column="name" type="string" length="50" not-null="true" unique="false"/> <set name="courses" table="student_course" cascade="save-update"> <key column="sid"></key> <many-to-many class="Course" column="cid"></many-to-many> </set> </class> </hibernate-mapping>
11.在src目录中创建工具类 HbnUtil,包名(com.mycompany.demo.util),如图所示
12.工具类 HbnUtil的内容如下
package com.mycompany.demo.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HbnUtil {
private static SessionFactory sessionFactory;
public static Session getSession(){
if(sessionFactory == null || sessionFactory.isClosed()){
sessionFactory = new Configuration().configure().buildSessionFactory();
}
return sessionFactory.getCurrentSession();
}
}13.在src目录中创建Hibernate的配置文件hibernate.cfg.xml,如图所示
14.Hibernate的配置文件hibernate.cfg.xml的内容如下
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-configuration SYSTEM "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- 方言,可以从Hibernate核心jar(hibernate-core-x.x.x.Finall.jar) 文件中的or.hibernate.dialect包中找到相应的类,类的全名就是 --> <property name="hibernate.dialect">org.hibernate.dialect.mysqlDialect</property> <!-- 驱动 --> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <!-- 数据库连接地址 --> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test</property> <!-- 用户名 --> <property name="hibernate.connection.username"> root </property> <!-- 密码 --> <property name="hibernate.connection.password"></property> <!-- create:每次都新创建,如果存在就删除 create-drop:创建新表,sessionFactory关闭,表会删除 update :表字段增加,会同步,字段减少不同步,数据改变会同步修改 --> <property name="hibernate.hbm2ddl.auto">update</property> <!-- 输出sql --> <property name="hibernate.show_sql">true</property> <!-- 格式化sql --> <property name="hibernate.format_sql">true</property> <!-- 事务环境一个线程对一个事务 thread:本地事务环境 jta:分布式事务环境 SpringSessionContext:用于ssh整合 --> <property name="hibernate.current_session_context_class">thread</property> <!-- 使用c3p0数据源 --> <property name="hibernate.connection.provider_class"> org.hibernate.c3p0.internal.C3P0ConnectionProvider</property> <!-- List of XML mapping files --> <mapping resource="com/mycompany/demo/bean/Course.hbm.xml"/> <mapping resource="com/mycompany/demo/bean/Student.hbm.xml"/> </session-factory> </hibernate-configuration>
15.在项目中创建test目录存储测试文件,文件名称TestApp,包名(com.mycompany.demo.bean),目录结构如图所示
16.TestApp测试类的内容如下
package com.mycompany.demo.bean;
import java.util.HashSet;
import java.util.Set;
import org.hibernate.Session;
import org.junit.Before;
import org.junit.Test;
import com.mycompany.demo.util.HbnUtil;
public class TestApp {
private Session session;
@Before
public void init(){
session = HbnUtil.getSession();
}
/*
* 双向关联-多对多(n:n)
*/
@Test
public void testManyToMany(){
try {
session.beginTransaction();
Course course1 = new Course("maven");
Student student = new Student("xiaoxiao");
Set<Student> students = new HashSet<Student>();
students.add(student);
course1.setStudents(students);
session.save(course1);
session.getTransaction().commit();
} catch (Exception e) {
session.getTransaction().rollback();
e.printStackTrace();
}
}
}
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