Hibernate 父子关系的级联保存

最新推荐文章于 2022-04-30 23:36:11 发布

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#hibernate #user #encoding #table #insert #string

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本文介绍了一个简单的用户表和学生表的关系模型及其在Hibernate框架中的对象-关系映射实现方式，包括对应的Java实体类定义和XML配置文件。

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（1）对应表及对象

父表：user

create table user(

id int auto_increment primary key,

username char(15),

password char(15)

)

父对象:

package com.ckcs.db.entry;

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

/**
 * User entity.
 * 
 * @author MyEclipse Persistence Tools
 */

public class User implements java.io.Serializable {

    // Fields

    private Integer id;
    private String password;
    private String username;
    private Set students = new HashSet(0);

    // Constructors

    /** default constructor */
    public User() {
    }

    /** full constructor */
    public User(String password, String username, Set students) {
        this.password = password;
        this.username = username;
        this.students = students;
    }

    // Property accessors

    public Integer getId() {
        return this.id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return this.username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Set getStudents() {
        return this.students;
    }

    public void setStudents(Set students) {
        this.students = students;       
    }

    public Student getOnlyStudent() {
        Student student = null;
        if (students.size() > 0) {
            student = (Student) new LinkedList(students).getFirst();
        }
        return student;
    }

    public String toString() {
        Student student = null;
        if (students.size() > 0) {
            student = (Student) new LinkedList(students).getFirst();
        }
        return "user: username = " + username + " password = " + password
                + " students: " + student;
    }
}

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子表:

create table student(

stuId int primary key,

address char(50),

foreign key (stuId) references user(id)

)

子对象:

package com.ckcs.db.entry;

/**
 * Student entity.
 * 
 * @author MyEclipse Persistence Tools
 */

public class Student implements java.io.Serializable {

    // Fields

    private Integer stuId;
    private User user;
    private String address;

    // Constructors

    /** default constructor */
    public Student() {
    }

    /** minimal constructor */
    public Student(Integer stuId, User user) {
        this.stuId = stuId;
        this.user = user;
    }

    /** full constructor */
    public Student(Integer stuId, User user, String address) {
        this.stuId = stuId;
        this.user = user;
        this.address = address;
    }

    // Property accessors

    public Integer getStuId() {
        return this.stuId;
    }

    public void setStuId(Integer stuId) {
        this.stuId = stuId;
    }

    public User getUser() {
        return this.user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public String getAddress() {
        return this.address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String toString() {
        return "id = " + stuId + " address = " + address;
    }

}

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(2)对应的hibernate o/r映射文件

User.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">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.ckcs.db.entry.User" table="user" catalog="hibernate">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native"></generator>
        </id>
        <property name="password" type="java.lang.String">
            <column name="password" length="50" />
        </property>
        <property name="username" type="java.lang.String">
            <column name="username" length="50" />
        </property>
        <set name="students" inverse="true" cascade="all">
            <key>
                <column name="stuId" not-null="true" unique="true" />
            </key>
            <one-to-many class="com.ckcs.db.entry.Student" />
        </set>
    </class>
</hibernate-mapping>

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Student.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">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.ckcs.db.entry.Student" table="student" catalog="hibernate">
        <id name="stuId" type="java.lang.Integer">
            <column name="stuId" />
            <!-- 表示主键是个外键，与子关联的的对象是父对象是user，这样在插入student时将会使用user的主键作为自己的主键-->
            <generator class="foreign">
                <param name="property">user</param>
            </generator>
            
        </id>
        <many-to-one name="user" class="com.ckcs.db.entry.User" update="false" insert="false" fetch="select">
            <column name="stuId" not-null="true" unique="true" />
        </many-to-one>
        <property name="address" type="java.lang.String">
            <column name="address" length="50" />
        </property>
    </class>
</hibernate-mapping>

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（3）测试:

package com.ckcs.test;
import org.hibernate.Session;
import com.ckcs.HibernateSessionFactory;
import com.ckcs.db.entry.Student;
import com.ckcs.db.entry.User;

public class Test {
    public void saveUser() {
        Session session = HibernateSessionFactory.getSession();
        session.beginTransaction();
            
        User user = new User();
        user.setUsername("小王");
        user.setPassword("000");
        
        Student studnet = new Student();        
        studnet.setAddress("小路旁");

        //子类关联父类
        studnet.setUser(user);
        //父类关联子类
        user.getStudents().add(studnet);

        session.save(user);
        session.getTransaction().commit();
    }

    public static void main(String[] args) {
        Test test = new Test();
        test.saveUser();
    }
}