Question

您好我有一个类车辆是父类，两个Wheeler和Four Wheeler是子类，它扩展了父类。
问题是当我将数据插入数据库中的 rto（id，name，vehicle_type，steeringHandle，steeringWheel）表时，它正在为 TwoWheeler 插入已分配的数据但是对于 FourWheeler ，它插入了父类中存在的方法的数据，但是当我从子类（FourWheeler（setsteeringWheel））调用方法时，它没有更新指定的中的数据 steeringWheel专栏。我正在添加表格的屏幕截图
车辆类 `

package hibernate_discriminator;

import java.io.Serializable;


public class Vehicle implements Serializable {
    private int id;
    private String name;

    public Vehicle(){

    }

    public int getId(){
        return id;
    }

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

    public void setName(String name){
        this.name= name;
    }

    public String getName(){
        return name;
    }


}

TwoWheeler Class

`package hibernate_discriminator;


public class TwoWheeler extends Vehicle{

    private String steeringHandle;

    public TwoWheeler(){

    }

    public void setsteeringHandle(String handle){
        this.steeringHandle= handle;
    }

    public String getsteeringHandle(){
        return steeringHandle;
    }


}
`

FourWheeler Class

package hibernate_discriminator;


public class FourWheeler extends Vehicle {

    private String steeringWheel;

    public FourWheeler(){

    }

    public void setsteeringWheel(String wheel){
        this.steeringWheel= steeringWheel;
    }

    public String getsteeringWheel(){
        return steeringWheel;
    }


}

映射文件

 <?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>
    <class name="hibernate_discriminator.Vehicle" table="rto" discriminator-value="vehicle">
        <id name="id" column="id" type="integer">
            <generator class="increment"></generator>
        </id>

        <discriminator column="vehicle_type" type="string"></discriminator>
        <property name="name" column="name" type="string"></property>

        <subclass name="hibernate_discriminator.TwoWheeler" extends="Vehicle" discriminator-value="Bike">
            <property name="steeringHandle" column="steeringHandle" type="string"></property>
        </subclass>
        <subclass name="hibernate_discriminator.FourWheeler" extends="Vehicle" discriminator-value="Car">
            <property name="steeringWheel" column="steeringWheel" type="string"></property>
        </subclass>
    </class>
</hibernate-mapping>

配置文件

    <?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">ankita</property>
        <property name="hibernate.connection.autocommit">false</property>

        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <property name="use_sql_comments">true</property>

        <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>

        <mapping resource="resources/Vehicle.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

主类

   public class Main {
    public static void main(String[] args){
        Configuration cfg= new Configuration();
        cfg.configure("/resources/Config.cfg.xml");
        SessionFactory sf= cfg.buildSessionFactory();
        Session s= sf.openSession();
        Transaction tx= s.beginTransaction();

        Vehicle v= new Vehicle();
        v.setName("Vehicle");

        TwoWheeler tw= new TwoWheeler();
        tw.setName("CBR");
        tw.setsteeringHandle("CBR Handle");

        FourWheeler fw= new FourWheeler();
        fw.setName("Audi A4");
        fw.setsteeringWheel("Audi a7 Wheel");

        s.save(v);
        s.save(tw);
        s.save(fw);
        s.flush();
        tx.commit();
    }
}

添加我的数据库scrrenshot

FourWheeler Class

   public class Main {
    public static void main(String[] args){
        Configuration cfg= new Configuration();
        cfg.configure("/resources/Config.cfg.xml");
        SessionFactory sf= cfg.buildSessionFactory();
        Session s= sf.openSession();
        Transaction tx= s.beginTransaction();

        Vehicle v= new Vehicle();
        v.setName("Vehicle");

        TwoWheeler tw= new TwoWheeler();
        tw.setName("CBR");
        tw.setsteeringHandle("CBR Handle");

        FourWheeler fw= new FourWheeler();
        fw.setName("Audi A4");
        fw.setsteeringWheel("Audi a7 Wheel");

        s.save(v);
        s.save(tw);
        s.save(fw);
        s.flush();
        tx.commit();
    }
}

Answer 1

我认为你的问题就在这里......

public void setsteeringWheel(String wheel){
    this.steeringWheel= steeringWheel;
}

方法参数为wheel，但您指定的值为steeringWheel。（您正在分配this.steeringWheel = steeringWheel，这意味着在调用null后，它将具有相同的值setsteeringWheel()。）

Answer 2

问题在这里

public void setsteeringWheel(String wheel){
        this.steeringWheel= steeringWheel;
    }

您没有使用传递的参数 this.steeringWheel = wheel;

数据未插入指定的列

2 个答案: