8.Hibernate的多对多关联映射

1.创建如下数据库脚本

 1 --1.1 项目表
 2 create table PROJECT
 3 (
 4   proid   NUMBER(6) not null,
 5   proname VARCHAR2(50)
 6 )
 7 ;
 8 --1.2 项目表主键
 9 alter table PROJECT
10   add constraint PK_PROJECT_PROID primary key (PROID);
11 
12 
13 --2.1 员工表
14 create table EMPLOYEE
15 (
16   empid   NUMBER(6) not null,
17   empname VARCHAR2(50)
18 )
19 ;
20 
21 --2.2 员工表主键
22 alter table EMPLOYEE
23   add constraint PK_EMPLOYEE_EMPID primary key (EMPID);
24 
25 --3.1中间表
26 create table PROEMP
27 (
28   rproid NUMBER(6) not null,
29   rempid NUMBER(6) not null
30 )
31 ;
32 --3.2 中间表主外健
33 alter table PROEMP
34   add constraint PK_PROEMP primary key (RPROID, REMPID);
35 
36 alter table PROEMP
37   add constraint FK_PROEMP_REMPID foreign key (REMPID)
38   references EMPLOYEE (EMPID);
39 
40 alter table PROEMP
41   add constraint FK_PROEMP_RPROID foreign key (RPROID)
42   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

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd" >
 3 <hibernate-configuration>
 4   <session-factory>
 5      <!-- 数据库就的url地址 -->
 6      <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>
 7      
 8      <property name="dialect"> org.hibernate.dialect.Oracle10gDialect</property>
 9      
10      <!-- 数据库驱动 -->
11      <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
12      
13      <!-- 数据库用户名 -->
14      <property name="connection.username">scott</property>
15      
16      <!-- 数据库密码 -->
17      <property name="connection.password">tiger</property>
18      
19  
20      <!-- 显示sql语句 -->
21      <property name="show_sql">true</property>
22      
23      <!-- sql语句格式化 -->
24      <property name="format_sql">true</property>
25      
26      <!-- 注册映射文件 -->
27      <mapping resource="com/entity/Project.hbm.xml"/>
28      <mapping resource="com/entity/Employee.hbm.xml"/>
29   </session-factory>
30   
31 </hibernate-configuration>
hibernate.cfg.xml

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

 1 package com.entity;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 public class Employee {
 7     private Integer empid;
 8     private String empname;
 9     private Set<Project> projects=new HashSet<Project>();
10     
11     public Employee() {
12     }
13 
14     public Employee(Integer empid, String empname) {
15         this.empid = empid;
16         this.empname = empname;
17     }
18     
19 
20     public Employee(Integer empid, String empname, Set<Project> projects) {
21         this.empid = empid;
22         this.empname = empname;
23         this.projects = projects;
24     }
25 
26     public Integer getEmpid() {
27         return empid;
28     }
29 
30     public void setEmpid(Integer empid) {
31         this.empid = empid;
32     }
33 
34     public String getEmpname() {
35         return empname;
36     }
37 
38     public void setEmpname(String empname) {
39         this.empname = empname;
40     }
41 
42     public Set<Project> getProjects() {
43         return projects;
44     }
45 
46     public void setProjects(Set<Project> projects) {
47         this.projects = projects;
48     }
49 
50     @Override
51     public String toString() {
52         return "Employee [empid=" + empid + ", empname=" + empname
53                 + ", projects=" + projects + "]";
54     }
55     
56 
57 }
Employee.java

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

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
 3 <hibernate-mapping>
 4    <!-- 持久化类的映射文件 -->
 5    <class name="com.entity.Employee" table="EMPLOYEE">
 6       <!-- 主键映射 -->
 7       <id name="empid" type="java.lang.Integer" column="empid">
 8          <!-- 主键插入由应用程序负责生成 -->
 9          <generator class="assigned"/>
10       </id>
11       <!-- 普通字段映射 -->
12       <!-- 员工名称称映射 -->
13       <property name="empname" type="java.lang.String" column="EMPNAME"/>
14       
15       <!-- 多对多 中间表字段-->
16      <set name="projects" table="PROEMP" inverse="true">
17         <!-- 中间表和员工表关联的外键字段 -->
18          <key column="REMPID"></key>
19          
20          <!-- 员工中的项目集合 -->
21          <many-to-many class="com.entity.Project" column="RPROID"/>
22       </set>
23    </class>
24 </hibernate-mapping>
Employee.hbm.xml

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

 1 package com.entity;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 public class Project {
 7     private Integer proid;
 8     private String proname;
 9     private Set<Employee> employees=new HashSet<Employee>();
10     
11     
12     public Project() {
13     }
14     public Project(Integer proid, String proname) {
15         this.proid = proid;
16         this.proname = proname;
17     }
18     
19     public Project(Integer proid, String proname, Set<Employee> employees) {
20         this.proid = proid;
21         this.proname = proname;
22         this.employees = employees;
23     }
24     public Integer getProid() {
25         return proid;
26     }
27     public void setProid(Integer proid) {
28         this.proid = proid;
29     }
30     public String getProname() {
31         return proname;
32     }
33     public void setProname(String proname) {
34         this.proname = proname;
35     }
36     
37     public Set<Employee> getEmployees() {
38         return employees;
39     }
40     public void setEmployees(Set<Employee> employees) {
41         this.employees = employees;
42     }
43     @Override
44     public String toString() {
45         return "Project [employees=" + employees + ", proid=" + proid
46                 + ", proname=" + proname + "]";
47     }
48     
49     
50 
51 }
Project.java

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

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

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

 1 package com.util;
 2 
 3 import org.hibernate.HibernateException;
 4 import org.hibernate.Session;
 5 import org.hibernate.SessionFactory;
 6 import org.hibernate.cfg.Configuration;
 7 
 8 public class HibernateUtil {
 9     /*
10      * 1.创建用线程管理session的对象 还要导入org.hibernate.Session资源
11      */
12     private static final ThreadLocal<Session> threadLoad = new ThreadLocal<Session>();
13 
14     /*
15      * 2.定义读取配置文件的对象
16      */
17     private static Configuration configuration = null;
18 
19     /*
20      * 3.定义SessionFacotry工厂对象
21      */
22     private static SessionFactory sessionFactory = null;
23 
24     /*
25      * 4.读取配置文件
26      */
27     static {
28         try {
29             // 读取配置文件
30             configuration = new Configuration().configure();
31 
32             // 创建session工厂对象
33             sessionFactory = configuration.buildSessionFactory();
34         } catch (HibernateException e) {
35             System.out.println("创建sessionFactory工厂对象错误");
36             e.printStackTrace();
37         }
38     }
39 
40     /**
41      * 5.获取Session对象
42      * @return session对象
43      */
44     public static Session getSession() {
45         // 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
46         Session session = threadLoad.get();
47 
48         // 如果获取的session为null则新打开session
49         if (session == null) {
50             // 打开一个新的Session
51             session = sessionFactory.openSession();
52 
53             // 将session对象保存到线程中
54             threadLoad.set(session);
55         }
56         // 返回从线程中获取的session对象
57         return session;
58     }
59     
60     /**
61      * 6.关闭session对象
62      */
63     public static void closeSession(){
64         //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
65         Session session=threadLoad.get();
66         
67         //将线程中的session置空
68         threadLoad.set(null);
69         
70         //如果session不为空，则关闭session
71         if(session!=null){
72             //关闭session
73             session.close();
74         }
75         
76         
77     }
78 
79 }
HibernateUtil.java

9.在项目的src下的com.dao包下创建ProEmpDao.java类

 1 package com.dao;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.Transaction;
 5 
 6 import com.entity.Employee;
 7 import com.entity.Project;
 8 import com.util.HibernateUtil;
 9 
10 public class ProEmpDao {
11     public static void main(String[] args) {
12         //开启session
13         Session session=HibernateUtil.getSession();
14         //开启事务
15         Transaction tx=session.beginTransaction();
16         //创建多个员工
17         Employee emp1=new Employee(1, "张三");
18         Employee emp2=new Employee(2, "李四");
19         
20         //创建项目存在
21         Project p1=new Project(1, "1号项目");
22         Project p2=new Project(2, "2号项目");
23         
24         //多个人负责一个项目
25         p1.getEmployees().add(emp1);
26         p1.getEmployees().add(emp2);
27         
28         //一个项目多个人负责
29         emp1.getProjects().add(p1);
30         emp2.getProjects().add(p1);
31         
32         //一个人负责多个项目
33         p2.getEmployees().add(emp1);
34         
35         //一个项目一个人负责
36         emp1.getProjects().add(p2);
37         
38         //保存项目时级联保存人信息
39         session.save(p1);
40         session.save(p2);
41         
42         tx.commit();
43         HibernateUtil.closeSession();
44         
45         
46     }
47 
48 }
ProEmpDao.java
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原文地址：https://www.cnblogs.com/holly8/p/5774379.html