Hibernate 冬眠：“；实例化异常：无法实例化抽象类或接口；

我的班级结构如下：

public class MailAccount{
 IncomingMailServer incomingServer;
 OutgoingMailServer outgoingServer;
}

public class MailServer{
 HostAddress hostAddress;
 Port port;
}

public class IncomingMailServer extends MailServer{
 // ...
}

public class OutgoingMailServer extends MailServer{
 // ...
}

public class ImapServer extends IncomingMailServer{
 // ...
}

public class Pop3Server extends IncomingMailServer{
 // ...
}

public class SmtpServer extends OutgoingMailServer{
 // ...
}

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

我的（简化）映射文件如下所示：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.mail.account">
    <class name="MailAccount" table="MAILACCOUNTS" dynamic-update="true">

        <id name="id" column="MAIL_ACCOUNT_ID">
            <generator class="native" />
        </id>

        <component name="incomingServer">
            <component name="hostAddress">
                <property name="address" column="IS_HOST_ADDRESS"></property>
            </component>

            <component name="port">
                <property name="portNumber" column="IS_PORT_NUMBER"></property>
            </component>
        </component>

        <component name="outgoingServer">
            <component name="hostAddress">
                <property name="address" column="OS_HOST_ADDRESS"></property>
            </component>

            <component name="port">
                <property name="portNumber" column="OS_PORT_NUMBER"></property>
            </component>
        </component>

    </class>
</hibernate-mapping>

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

因此，我在incomingServer组件中添加了以下行：

<discriminator column="SERVER_TYPE" type="string"/>
<subclass name="ImapServer" extends="IncomingMailServer" discriminator-value="IMAP_SERVER" />           
<subclass name="Pop3Server" extends="IncomingMailServer" discriminator-value="POP3_SERVER" />

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

显然，Hibernate不喜欢组件中的这些标记

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

我如何解决这个问题？

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

---

Ps:我已经尝试将IncomingServer和OutgoingServer分别移动到各自的表中，并通过一对一映射它们。这是可行的，但会导致数据库不一致，因为我注意到MailAccount和IncomingServer/OutgoingServer必须始终具有相同的主键id。否则，所有内容都将不同步，主键的自动增量值不再匹配（在MailAccount和服务器之间）。

我的方法是：

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

• 创建一个实体（具有自己的映射）带有鉴别器和全部的MailServer。把它标成抽象的，只是为了确定
• 使用自己的鉴别器创建MailServer的层次结构（每个hbm一个）
• 将具有2个一对一关系的MailAccount映射到MailServer。一个传入，一个传出

---

请给我们看更多的代码。如果不知道，很难提供帮助：）

这个映射对我很有用：

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

休眠映射

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

让我知道这是否解决了问题。：）

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

编辑：添加了从MailAccount到MailServer的映射。

<class name="MailServer" abstract="true" table="SERVER">
    <id name="id" column="id">
        <generator class="native" />
    </id>
    <discriminator column="SERVER_TYPE" type="string"/>
    <subclass name="IncomingMailServer" abstract="true">
        <property name="address" column="IS_HOST_ADDRESS"></property>
        <property name="portNumber" column="IS_PORT_NUMBER"></property>
    </subclass>           
    <subclass name="OutgoingMailServer" abstract="true">
           <property name="address" column="OS_HOST_ADDRESS"></property>
           <property name="portNumber" column="OS_PORT_NUMBER"></property>
    </subclass>           
</class>

<subclass name="IMAPServer" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="IMAP_SERVER"/>
<subclass name="POP3Server" extends="com.mail.account.IncomingMailServer" 
          discriminator-value="POP3_SERVER"/>
<subclass name="SMTPServer" extends="com.mail.account.OutgoingMailServer" 
          discriminator-value="SMTP_SERVER" />

是的，但是如何在MailAccount和MailServer之间进行映射？我已经编辑了答案以添加映射；如果你有任何疑问，请告诉我。是的，这很有效。最后一个问题：为什么在这里使用多对一而不是一对一？好吧，我可以使用一对一但多对一，使用unique=true的方式也一样！谢谢你的接受，该死，我错过了赏金！！：-）正如我在最初的问题中所说的那样。一对一导致数据库不一致。这种情况是对单个表的一对一。您可以使用相同的id。是的，问题是两个id列都设置了自动增量标志。因此，每当“id”的下一个自动增量值在MailAccount id和MailServer id之间不同步时，一切都会变得一团糟。