8.Hibernate的多对多关联映射

1.创建如下数据库脚本

 --1.1 项目表
 create table PROJECT
 (
   proid   NUMBER(6) not null,
   proname VARCHAR2(50)
 )
 ;
 --1.2 项目表主键
 alter table PROJECT
   add constraint PK_PROJECT_PROID primary key (PROID);

 --2.1 员工表
 create table EMPLOYEE
 (
   empid   NUMBER(6) not null,
   empname VARCHAR2(50)
 )
 ;

 --2.2 员工表主键
 alter table EMPLOYEE
   add constraint PK_EMPLOYEE_EMPID primary key (EMPID);

 --3.1中间表
 create table PROEMP
 (
   rproid NUMBER(6) not null,
   rempid NUMBER(6) not null
 )
 ;
 --3.2 中间表主外健
 alter table PROEMP
   add constraint PK_PROEMP primary key (RPROID, REMPID);

 alter table PROEMP
   add constraint FK_PROEMP_REMPID foreign key (REMPID)
   references EMPLOYEE (EMPID);

 alter table PROEMP
   add constraint FK_PROEMP_RPROID foreign key (RPROID)
   references PROJECT (PROID);

2.创建javaweb项目Hibernate_Part4_C2

3. 在项目的src下创建hibernate.cfg.xml的主配置文件

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd" >
 <hibernate-configuration>
   <session-factory>
      <!-- 数据库就的url地址 -->
      <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>

      <property name="dialect"> org.hibernate.dialect.Oracle10gDialect</property>

      <!-- 数据库驱动 -->
      <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

      <!-- 数据库用户名 -->
      <property name="connection.username">scott</property>

      <!-- 数据库密码 -->
      <property name="connection.password">tiger</property>

      <!-- 显示sql语句 -->
      <property name="show_sql">true</property>

      <!-- sql语句格式化 -->
      <property name="format_sql">true</property>

      <!-- 注册映射文件 -->
      <mapping resource="com/entity/Project.hbm.xml"/>
      <mapping resource="com/entity/Employee.hbm.xml"/>
   </session-factory>

 </hibernate-configuration>

hibernate.cfg.xml

4.在项目的src下的com.entity包下创建Employee.java类

 package com.entity;

 import java.util.HashSet;
 import java.util.Set;

 public class Employee {
     private Integer empid;
     private String empname;
     private Set<Project> projects=new HashSet<Project>();

     public Employee() {
     }

     public Employee(Integer empid, String empname) {
         this.empid = empid;
         this.empname = empname;
     }

     public Employee(Integer empid, String empname, Set<Project> projects) {
         this.empid = empid;
         this.empname = empname;
         this.projects = projects;
     }

     public Integer getEmpid() {
         return empid;
     }

     public void setEmpid(Integer empid) {
         this.empid = empid;
     }

     public String getEmpname() {
         return empname;
     }

     public void setEmpname(String empname) {
         this.empname = empname;
     }

     public Set<Project> getProjects() {
         return projects;
     }

     public void setProjects(Set<Project> projects) {
         this.projects = projects;
     }

     @Override
     public String toString() {
         return "Employee [empid=" + empid + ", empname=" + empname
                 + ", projects=" + projects + "]";
     }

 }

Employee.java

5.在项目的src下的com.entity包下创建Employee.hbm.xml映射文件

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
 <hibernate-mapping>
    <!-- 持久化类的映射文件 -->
    <class name="com.entity.Employee" table="EMPLOYEE">
       <!-- 主键映射 -->
       <id name="empid" type="java.lang.Integer" column="empid">
          <!-- 主键插入由应用程序负责生成 -->
          <generator class="assigned"/>
       </id>
       <!-- 普通字段映射 -->
       <!-- 员工名称称映射 -->
       <property name="empname" type="java.lang.String" column="EMPNAME"/>

       <!-- 多对多 中间表字段-->
      <set name="projects" table="PROEMP" inverse="true">
         <!-- 中间表和员工表关联的外键字段 -->
          <key column="REMPID"></key>

          <!-- 员工中的项目集合 -->
          <many-to-many class="com.entity.Project" column="RPROID"/>
       </set>
    </class>
 </hibernate-mapping>

Employee.hbm.xml

6.在项目的src下的com.entity包下创建Project.java类

 package com.entity;

 import java.util.HashSet;
 import java.util.Set;

 public class Project {
     private Integer proid;
     private String proname;
     private Set<Employee> employees=new HashSet<Employee>();

     public Project() {
     }
     public Project(Integer proid, String proname) {
         this.proid = proid;
         this.proname = proname;
     }

     public Project(Integer proid, String proname, Set<Employee> employees) {
         this.proid = proid;
         this.proname = proname;
         this.employees = employees;
     }
     public Integer getProid() {
         return proid;
     }
     public void setProid(Integer proid) {
         this.proid = proid;
     }
     public String getProname() {
         return proname;
     }
     public void setProname(String proname) {
         this.proname = proname;
     }

     public Set<Employee> getEmployees() {
         return employees;
     }
     public void setEmployees(Set<Employee> employees) {
         this.employees = employees;
     }
     @Override
     public String toString() {
         return "Project [employees=" + employees + ", proid=" + proid
                 + ", proname=" + proname + "]";
     }

 }

Project.java

7.在项目的src下的com.entity包下创建Project.hbm.xml映射文件

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
 <hibernate-mapping>
    <!-- 持久化类的映射文件 -->
    <class name="com.entity.Project" table="PROJECT">
      <!-- 主键映射 -->
       <id name="proid" type="java.lang.Integer" column="PROID">
          <!-- 主键插入由应用程序负责生成 -->
          <generator class="assigned"/>
       </id>
       <!-- 普通字段映射 -->
       <!-- 项目名称称映射 -->
       <property name="proname" type="java.lang.String" column="PRONAME"/>
       <set name="employees" table="PROEMP" cascade="save-update">
       <!-- 中间表和项目表关联的外键字段 -->
          <key column="RPROID"></key>
          <many-to-many class="com.entity.Employee" column="REMPID"/>
       </set>
    </class>
 </hibernate-mapping>

Project.hbm.xml

8.在项目的src下的com.util包下创建HibernateUtil.java类

 package com.util;

 import org.hibernate.HibernateException;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.cfg.Configuration;

 public class HibernateUtil {
     /*
      * 1.创建用线程管理session的对象 还要导入org.hibernate.Session资源
      */
     private static final ThreadLocal<Session> threadLoad = new ThreadLocal<Session>();

     /*
      * 2.定义读取配置文件的对象
      */
     private static Configuration configuration = null;

     /*
      * 3.定义SessionFacotry工厂对象
      */
     private static SessionFactory sessionFactory = null;

     /*
      * 4.读取配置文件
      */
     static {
         try {
             // 读取配置文件
             configuration = new Configuration().configure();

             // 创建session工厂对象
             sessionFactory = configuration.buildSessionFactory();
         } catch (HibernateException e) {
             System.out.println("创建sessionFactory工厂对象错误");
             e.printStackTrace();
         }
     }

     /**
      * 5.获取Session对象
      * @return session对象
      */
     public static Session getSession() {
         // 获取当前线程内对应的session对象，可以保证每个线程都有自己的session独享
         Session session = threadLoad.get();

         // 如果获取的session为null则新打开session
         if (session == null) {
             // 打开一个新的Session
             session = sessionFactory.openSession();

             // 将session对象保存到线程中
             threadLoad.set(session);
         }
         // 返回从线程中获取的session对象
         return session;
     }

     /**
      * 6.关闭session对象
      */
     public static void closeSession(){
         //获取当前线程内对应的session对象，可以保证每个线程对象都有自己的session对象
         Session session=threadLoad.get();

         //将线程中的session置空
         threadLoad.set(null);

         //如果session不为空，则关闭session
         if(session!=null){
             //关闭session
             session.close();
         }

     }

 }

HibernateUtil.java

9.在项目的src下的com.dao包下创建ProEmpDao.java类

 package com.dao;

 import org.hibernate.Session;
 import org.hibernate.Transaction;

 import com.entity.Employee;
 import com.entity.Project;
 import com.util.HibernateUtil;

 public class ProEmpDao {
     public static void main(String[] args) {
         //开启session
         Session session=HibernateUtil.getSession();
         //开启事务
         Transaction tx=session.beginTransaction();
         //创建多个员工
         Employee emp1=new Employee(1, "张三");
         Employee emp2=new Employee(2, "李四");

         //创建项目存在
         Project p1=new Project(1, "1号项目");
         Project p2=new Project(2, "2号项目");

         //多个人负责一个项目
         p1.getEmployees().add(emp1);
         p1.getEmployees().add(emp2);

         //一个项目多个人负责
         emp1.getProjects().add(p1);
         emp2.getProjects().add(p1);

         //一个人负责多个项目
         p2.getEmployees().add(emp1);

         //一个项目一个人负责
         emp1.getProjects().add(p2);

         //保存项目时级联保存人信息
         session.save(p1);
         session.save(p2);

         tx.commit();
         HibernateUtil.closeSession();

     }

 }

ProEmpDao.java