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Hibernate多對多雙向關聯的配置，hibernate多對關聯

編輯：JAVA綜合教程

Hibernate多對多雙向關聯的配置，hibernate多對關聯

Hibernate的雙向多對多關聯有兩種配置方法:那我們就來看看兩種方案是如何配置的。

一、創建以各自類為類型的集合來關聯

1.首先我們要在兩個實體類(雇員<Emploee>、工程<Project>)中各自給對方添加一個對方的集合

1.1 雇員實體類

package cn.manytomany.one;

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

public class Emploee {
    //雇員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 工程實體類

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.有了實體類之後呢,我們就能通過實體的屬性和數據庫的表字段配置映射關系。

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 另外還有一個最重要的大配置來引用兩個小配置

<?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 二級緩存-->
        <!--<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>-->

        <!-- Echo all executed SQL to stdout 是否在控制台顯示sql語句-->
        <property name="show_sql">true</property>

        <!-- 格式化顯示SQL -->
        <property name="format_sql">true</property>

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

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

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

3.最後就是測試類了

package cn.manytomany.one;

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

public class ManyToManyDoubleTest {

    /**
     * 多對多的雙向關聯測試
     */
    public static void main(String[] args) {
        Session session = HibernateUtil.currentSession();
        Transaction tsc = session.beginTransaction();
        //創建雇員
        Emploee emp=new Emploee();
        emp.setEmpName("田超");
        Emploee emp1=new Emploee();
        emp1.setEmpName("施強");
        
        //創建工程
        Project pro=new Project();
        pro.setProName("開發工程");
        pro.getEmploees().add(emp);
        pro.getEmploees().add(emp1);
         try {
            session.save(pro);
            tsc.commit();
        } catch (Exception e) {
            // 回滾
            tsc.rollback();
        }
        HibernateUtil.closeSession();
    }

}

3.1 最後補充一下工具類,看看就行

package cn.manytomany.one;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.Session;
/*
 * session工具類
 */
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) {
            //異常
            e.printStackTrace();
            throw new ExceptionInInitializerError(e);
        }
    }
    public static Session currentSession(){
        Session session=sessionTL.get();
        //如果session為null,則打開一個新的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、創建一個中間的實體類來關聯

1.跟第一個方案差不多,先實現三個實體類,代碼如下:

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>(); //集合的類型為中間的實體類類型
    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;

   //集合的類型依然為中間的實體類類型
    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 補充的中間實體類

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. 接下來就是小配置了,跟第一個方案格式幾乎是一樣的,就不過多解釋了,直接來看小配置就行了。

因為我們要用中間實體類來關聯，所以雇員類（Emploee）和工程類(Project)沒有什麼眼添加的,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 關鍵就在於 proemp.hbm.xml (把多對多關聯轉化成兩個多對一來關聯)

<?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. 現在就可以進行測試類測試數據了

package cn.manytomany.doubleanother;

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

import cn.manytomany.one.HibernateUtil;


public class ManyToManyDoubleOnlyAnother {

    /**
     * 多對多雙向關聯---兩個多對一關聯
     */
    public static void main(String[] args) {
        Session session = HibernateUtil.currentSession();
        Transaction tsc = session.beginTransaction();
        //創建雇員
        Emploee emp=new Emploee();
        emp.setEmpName("田超");
        
        //創建工程
        Project pro=new Project();
        pro.setProName("開發工程");
        
        //中間類
        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) {
            // 回滾
            tsc.rollback();
        }
        HibernateUtil.closeSession();

    }

}

好了, Hibernate的多對多雙向關聯的兩種方案已經完成,如果覺得對你們有用的話,記得點個關注啊!!!