Hibernate多对多双向关联的配置

         Hibernate的双向多对多关联有两种配置方法:那我们就来看看两种方案是如何配置的。

         一、创建以各自类为类型的集合来关联

      1.首先我们要在两个实体类(雇员<Emploee>、工程<Project>)中各自给对方添加一个对方的集合

       1.1 雇员实体类

package cn.manytomany.one; import java.util.HashSet; import java.util.Set; public class Emploee { //雇员id private Integer empId;
  //工程 private String empName;
 //工程的集合 private Set<Project> projects=new HashSet<Project>(); public Set<Project> getProjects() { return projects; } public void setProjects(Set<Project> projects) { 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; } }

 

       1.2 工程实体类

package cn.manytomany.one; import java.util.HashSet; import java.util.Set; public class Project { private Integer proId; private String proName; private Set<Emploee> emploees=new HashSet<Emploee>(); public Set<Emploee> getEmploees() { return emploees; } public void setEmploees(Set<Emploee> emploees) { this.emploees = emploees; } 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; } }

 

 

      2.有了实体类之后呢,我们就能通过实体的属性和数据库的表字段配置映射关系。

      2.1 emploees.hbm.xml

<?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 package="cn.manytomany.one">
    <class name="Emploee" table="Emploee">
        <id name="empId">
        <generator class="sequence">
        <param name="sequence">SQU_NUM</param>
        </generator>
        </id>
        <property name="empName"></property>
        <set name="projects" table="PROEMP">
         <key column="RPROID"></key>
         <many-to-many class="Project" column="REMPID">
         </many-to-many>
        </set>
    </class>
</hibernate-mapping>

 

 

      2.2   projects.hbm.xml

<?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 package="cn.manytomany.one">
    <class name="Project" table="PROJECT">
        <id name="proId">
        <generator class="sequence">
        <param name="sequence">SQU_NUM</param>
        </generator>
        </id>
        <property name="proName"></property>
        
        <set name="emploees" table="PROEMP" cascade="save-update">
         <key column="REMPID"></key>
         <many-to-many class="Emploee" column="RPROID">
         </many-to-many>
        </set>
    </class>
</hibernate-mapping>

 

   

     2.3 另外还有一个最重要的大配置来引用两个小配置

<?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"> oracle.jdbc.OracleDriver </property>
        <property name="connection.url"> jdbc:oracle:thin:@localhost:1521:orcl </property>
        <property name="connection.username">happy</property>
        <property name="connection.password">1</property>

        <!-- SQL dialect 方言-->
        <property name="dialect"> org.hibernate.dialect.Oracle10gDialect </property>

        <!-- Disable the second-level cache 二级缓存-->
        <!--<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>-->

        <!-- Echo all executed SQL to stdout 是否在控制台显示sql语句-->
        <property name="show_sql">true</property>

        <!-- 格式化显示SQL -->
        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create</property>

        <!-- 关联小配置 -->
        <mapping resource="cn/manytomany/doubleanother/emploees.hbm.xml" />
        <mapping resource="cn/manytomany/doubleanother/projects.hbm.xml" />

    </session-factory>
</hibernate-configuration>

 

 

 

    3.最后就是测试类了

package cn.manytomany.one; import org.hibernate.Session; import org.hibernate.Transaction; public class ManyToManyDoubleTest { /** * 多对多的双向关联测试 */
    public static void main(String[] args) { Session session = HibernateUtil.currentSession(); Transaction tsc = session.beginTransaction(); //创建雇员
        Emploee emp=new Emploee(); emp.setEmpName("田超"); Emploee emp1=new Emploee(); emp1.setEmpName("施强"); //创建工程
        Project pro=new Project(); pro.setProName("开发工程"); pro.getEmploees().add(emp); pro.getEmploees().add(emp1); try { session.save(pro); tsc.commit(); } catch (Exception e) { // 回滚
 tsc.rollback(); } HibernateUtil.closeSession(); } }

 

 

     3.1 最后补充一下工具类,看看就行

package cn.manytomany.one; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.Session; /* * session工具类 */
public class HibernateUtil { private static final ThreadLocal<Session> sessionTL=new ThreadLocal<Session>(); private static Configuration cfg; private static final SessionFactory sf; static{ try { cfg=new Configuration().configure(); sf = cfg.buildSessionFactory(); } catch (Exception e) { //异常
 e.printStackTrace(); throw new ExceptionInInitializerError(e); } } public static Session currentSession(){ Session session=sessionTL.get(); //如果session为null,则打开一个新的session
        if (session==null) { session=sf.openSession(); sessionTL.set(session); } return session; } public static void closeSession(){ Session session=sessionTL.get(); sessionTL.set(null); session.close(); } }

 

 

     

     二、创建一个中间的实体类来关联

       1.跟第一个方案差不多,先实现三个实体类,代码如下:

package cn.manytomany.doubleanother; import java.util.HashSet; import java.util.Set; public class Emploee { private Integer empId; private String empName; private Set<ProEmp> proemp=new HashSet<ProEmp>(); //集合的类型为中间的实体类类型 public Set<ProEmp> getProemp() { return proemp; } public void setProemp(Set<ProEmp> proemp) { this.proemp = proemp; } 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; } }

 

 

package cn.manytomany.doubleanother; import java.util.HashSet; import java.util.Set; public class Project { private Integer proId; private String proName;

 //集合的类型依然为中间的实体类类型
 private Set<ProEmp> proemp=new HashSet<ProEmp>();

    public Set<ProEmp> getProemp() {
     return proemp;
   }
    public void setProemp(Set<ProEmp> proemp) {
     this.proemp = proemp;
   }
   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;
   }

}

 

 

     1.1  补充的中间实体类

    

package cn.manytomany.doubleanother;

public class ProEmp {
    
    private Integer id;
    private Emploee emp;
    private Project pro;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public Emploee getEmp() {
        return emp;
    }
    public void setEmp(Emploee emp) {
        this.emp = emp;
    }
    public Project getPro() {
        return pro;
    }
    public void setPro(Project pro) {
        this.pro = pro;
    }
    
}

 

 

     2. 接下来就是小配置了,跟第一个方案格式几乎是一样的,就不过多解释了,直接来看小配置就行了。

    因为我们要用中间实体类来关联，所以雇员类（Emploee）和工程类(Project)没有什么眼添加的,只需按照正常的配置即可。

    2.1 emploees.hbm.xml

<?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 package="cn.manytomany.doubleanother">
    <class name="Emploee" table="Emploee">
        <id name="empId">
        <generator class="sequence">
        <param name="sequence">SQU_NUM</param>
        </generator>
        </id>
        <property name="empName"></property>
    </class>
</hibernate-mapping>

 

  

    2.2  emploees.hbm.xml

<?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 package="cn.manytomany.doubleanother">
    <class name="Project" table="PROJECT">
        <id name="proId">
        <generator class="sequence">
        <param name="sequence">SQU_NUM</param>
        </generator>
        </id>
        <property name="proName"></property>
    </class>
</hibernate-mapping>

 

   

     2.3 关键就在于 proemp.hbm.xml   (把多对多关联转化成两个多对一来关联)

<?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 package="cn.manytomany.doubleanother">
    <class name="ProEmp" table="PROEMPNEW">
        <id name="id">
        <generator class="sequence">
        <param name="sequence">SQU_NUM</param>
        </generator>
        </id>
        <many-to-one name="emp" class="Emploee" column="EMPID"> </many-to-one> <many-to-one name="pro" class="Project" column="PROID"> </many-to-one>
    </class>
</hibernate-mapping>

 

 

    3. 现在就可以进行测试类测试数据了

package cn.manytomany.doubleanother; import org.hibernate.Session; import org.hibernate.Transaction; import cn.manytomany.one.HibernateUtil; public class ManyToManyDoubleOnlyAnother { /** * 多对多双向关联---两个多对一关联 */
    public static void main(String[] args) { Session session = HibernateUtil.currentSession(); Transaction tsc = session.beginTransaction(); //创建雇员
        Emploee emp=new Emploee(); emp.setEmpName("田超"); //创建工程
        Project pro=new Project(); pro.setProName("开发工程"); //中间类
        ProEmp proemp=new ProEmp(); proemp.setEmp(emp); proemp.setPro(pro); try { //保存
 session.save(emp); session.save(pro); session.save(proemp); tsc.commit(); } catch (Exception e) { // 回滚
 tsc.rollback(); } HibernateUtil.closeSession(); } }

 

 

     好了, Hibernate的多对多双向关联的两种方案已经完成,如果觉得对你们有用的话,记得点个关注啊!!!