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!!!