Hibernate一對多、多對一的關係表達

一、關係表達：

1、一對多、多對一表的關係：

學生表：

 

 

  班級表：

 

 

 在學生表中，學生的學號是主鍵。在班級表中，班級號是主鍵，因此，學生表的外鍵是classno。因此，班級對應學生是一對多，學生對應班級是多對一。因為，一個班級可以有多個學生，但是一個學生只能在一個班級。

2、對象的一對多、多對一關係：

（1）在Class類中，定義Set集合，表達一對多的關係：

 

 

 

package pers.zhb.domain;
import java.util.HashSet;
import java.util.Set;
public class Class {
    private String classno;
    private String department;
    private String monitor;
    private String classname;
    private Set<Student> classes=new HashSet<Student>();//使用set集合表達一對多關係
    public Class(){
    }
    public Set<Student> getClasses() {
        return classes;
    }
    public void setClasses(Set<Student> classes) {
        this.classes = classes;
    }
    public String getMonitor() {
        return monitor;
    }

    public void setMonitor(String monitor) {
        this.monitor = monitor;
    }

    public String getDepartment() {
        return department;
    }

    public void setDepartment(String department) {
        this.department = department;
    }



    public String getClassname() {
        return classname;
    }

    public void setClassname(String classname) {
        this.classname = classname;
    }
    public String getClassno() {
        return classno;
    }

    public void setClassno(String classno) {
        this.classno = classno;
    }
    @Override
    public String toString() {
        return "Class{" +
                "classno='" + classno + '\'' +
                ", department='" + department + '\'' +
                ", monitor='" + monitor + '\'' +
                ", classname='" + classname + '\'' +
                ", classes=" + classes +
                '}';
    }
}

package pers.zhb.domain;
public class Student {
    private Integer studentno;
    private String sname;
    private String sex;
    private String birthday;
    private String classno;
    private Float point;
    private String phone;
    private String email;
    private Clas aClas;
    public Student(){//無參的構造方法
    }
    public Clas getaClas() {
        return aClas;
    }

    public void setaClas(Clas aClas) {
        this.aClas = aClas;
    }
    @Override
    public String toString() {
        return "Student{" +
                "studentno='" + studentno + '\'' +
                ", sname='" + sname + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday='" + birthday + '\'' +
                ", classno='" + classno + '\'' +
                ", point=" + point +
                ", phone='" + phone + '\'' +
                ", email='" + email + '\'' +
                '}';
    }

    public int getStudentno() {
        return studentno;
    }

    public void setStudentno(int studentno) {
        this.studentno = studentno;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getClassno() {
        return classno;
    }

    public void setClassno(String classno) {
        this.classno = classno;
    }

    public float getPoint() {
        return point;
    }

    public void setPoint(float point) {
        this.point = point;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

　　

　　

（2）定義學生和班級的關係：

 

 

 

package pers.zhb.domain;
import java.util.HashSet;
import java.util.Set;
public class Clas {
    private String classno;
    private String department;
    private String monitor;
    private String classname;
    private Set<Student> students=new HashSet<Student>();//使用set集合表達一對多關係
    public Clas(){
    }
    public Set<Student> getStudents() {
        return students;
    }
    public void setClasses(Set<Student> students) {
        this.students = students;
    }
    public String getMonitor() {
        return monitor;
    }

    public void setMonitor(String monitor) {
        this.monitor = monitor;
    }

    public String getDepartment() {
        return department;
    }

    public void setDepartment(String department) {
        this.department = department;
    }



    public String getClassname() {
        return classname;
    }

    public void setClassname(String classname) {
        this.classname = classname;
    }
    public String getClassno() {
        return classno;
    }

    public void setClassno(String classno) {
        this.classno = classno;
    }
    @Override
    public String toString() {
        return "Class{" +
                "classno='" + classno + '\'' +
                ", department='" + department + '\'' +
                ", monitor='" + monitor + '\'' +
                ", classname='" + classname + '\'' +
                ",students=" + students +
                '}';
    }
}

　　

3、配置映射文件：

  Class.hbm.xml：

（1）實現一對多的關係映射，即：一個班級對應多個學生：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pers.zhb.domain">
    <class name="Clas" table="class">
        <id name="classno" column="classno">
            <generator class="native"></generator>
        </id><!--主鍵-->
        <property name="department" column="department"></property>
        <property name="monitor" column="monitor"></property>
        <property name="classname" column="classname"></property>
        <set name="students" table="student"><!--一對多關係配置-->
        <key column="classno" update="false"></key><!--指定了集合表的外鍵-->
            <one-to-many class="Student"></one-to-many>
        </set>
    </class>
</hibernate-mapping>

 

<set name="students">

指定映射的存儲學生的集合的名字。

<key column="classesno"></key>

映射的class表的外鍵。

<one-to-many class="Student"></one-to-many>

指定學生的類型。

（2）實現多對一的關係映射，即：多個學生對應一個班級。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pers.zhb.domain">
    <class name="Student" table="student">
        <id name="studentno" column="studentno" >
            <generator class="native"></generator>
        </id>
        <property name="birthday" column="birthday"></property>
        <property name="classno" column="classno" insert="false" update="false"></property>
        <property name="email" column="email"></property>
        <property name="phone" column="phone"></property>
        <property name="sex" column="sex"></property>
        <property name="sname" column="sname"></property>
        <property name="point" column="point"></property>
        <many-to-one name="aClas" column="classno" class="Clas"></many-to-one>
    </class>
</hibernate-mapping>

 

name屬性：映射的班級。

column屬性：映射的班級對象對應的外鍵。

class屬性：指定班級的類型。

4、主配置文件：

<?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>
    <!--配置數據庫信息-必須的-->
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/stu_mangement</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <!--配置hibernate信息-可選的-->
        <property name="hibernate.show_sql">true</property><!--輸出底層sql語句-->
        <property name="hibernate.format_sql">true</property><!--格式化輸出sql語句-->
        <property name="hibernate.hbm2ddl.auto">update</property><!--hibernate幫助創建表，如果已經有表更新表，如果沒有則創建新表-->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <property name="hibernate.connection.isolation">4</property>
        <!--指定session與當前線程綁定-->
        <property name="hibernate.current_session_context_class">thread</property>
        <!--配置數據庫的方言，讓hibernate識別框架自己的特有語句-->
        <!--把映射文件放到核心配置文件-->
        <mapping resource="pers/zhb/domain/Student.hbm.xml"/><!--都在src目錄下-->
        <mapping resource="pers/zhb/domain/Class.hbm.xml"/><!--都在src目錄下-->
    </session-factory>
</hibernate-configuration>

　二、具體運用：

1、增加：

（1）創建一個新班級併為新班級添加兩名學生：

public class Test {
    public static void testSel() {
            Session session = HibernateUtils.openSession();//獲得session
            Transaction transaction = session.beginTransaction();//開啟事務
            Clas clas=new Clas();
            clas.setClassname("計科171");
            clas.setClassno(4600);
            clas.setDepartment("一號樓");
            clas.setMonitor("zhai");

            Student student=new Student();
            student.setSname("翟");
            student.setStudentno(2017151411);
            student.setPoint(123f);
            student.setSex("男");
            student.setBirthday("2019-11-11");
            student.setPhone("18739496522");
            student.setClassno("221221");
            student.setEmail("34288334@qq.com");

            Student student1=new Student();
            student1.setSname("翟hb");
            student1.setStudentno(2017151419);
            student1.setPoint(666f);
            student1.setSex("女");
            student1.setBirthday("2019-11-11");
            student1.setPhone("18739496522");
            student1.setClassno("221221");
            student1.setEmail("34288334@qq.com");

            clas.getStudents().add(student);//一對多，一個班級下有多個學生
            clas.getStudents().add(student1);//獲取Set集合對象並向其中添加元素

            student.setaClas(clas);//多對一，學生屬於哪一個班級
            student1.setaClas(clas);

            session.save(clas);
            session.save(student);
            session.save(student1);

            transaction.commit();//提交事務
            session.close();//關閉資源
        }

 

 （2）為一個已經存在的班級添加學生：

 public static void testAdd(){
            Session session = HibernateUtils.openSession();//獲得session
            Transaction transaction = session.beginTransaction();//開啟事務
            Clas clas=session.get(Clas.class,80501);//獲得一個已經存在的班級
            Student student=new Student();//創建一個學生對象
            student.setSname("翟zz");
            student.setStudentno(20190000);
            student.setPoint(133f);
            student.setSex("男");
            student.setBirthday("2019-11-16");
            student.setPhone("18739496522");
            student.setEmail("34288334@qq.com");

            Student student1=new Student();//再創建一個學生對象
            student1.setSname("翟zz");
            student1.setStudentno(20190000);
            student1.setPoint(133f);
            student1.setSex("男");
            student1.setBirthday("2019-11-16");
            student1.setPhone("18739496522");
            student1.setEmail("34288334@qq.com");

            clas.getStudents().add(student);//學生添加到班級
            student.setaClas(clas);//班級與學生對應
            clas.getStudents().add(student1);
            student1.setaClas(clas);

            session.save(student);
            session.save(student1);


            transaction.commit();//提交事務
            session.close();//關閉資源

        }

　　

 

 2、刪除：

刪除80501班的一名學生信息：

 public static void testDel() {
           Session session = HibernateUtils.openSession();//獲得session
           Transaction transaction = session.beginTransaction();//開啟事務
           Clas clas=session.get(Clas.class,80501);//獲得要刪除的學生屬於那一個班級
           Student student=session.get(Student.class,937221532);//獲得要刪除的學生
           clas.getStudents().remove(student);
           student.setaClas(null);
           transaction.commit();//提交事務
           session.close();//關閉資源
       }

 

　

 

 

 

 

 

 

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