Question

我正在尝试使用Hibernate 5.0将以下对象映射到数据库表中。

class Ticket {

  private TicketId ticketId;
  private String description;

  private Ticket() {}
  private Ticket(final String description) {
    this.description = description;
  }
  public TicketId ticketId() { return ticketId; }
  public String description() { return description; }
  // equals and hashCode
}

其中TicketId是一个非常简单的包装主键，需要在数据库中自动生成：

class TicketId implements Serializable {

  private Long id;

  private TicketId() {}
  public Long id() { return id; }
  // equals and hashCode
}

MySQL数据库表架构如下：

CREATE TABLE `TICKETS` (
  `ID` INT(11) unsigned NOT NULL AUTO_INCREMENT,
  `DESCRIPTION` VARCHAR(255),
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB;

我已经读过the article by Vlad Michalcea，但是我想使用xml并想出了以下映射：

<?xml version="1.0"?>
<hibernate-mapping default-access="field" default-cascade="all"
  xmlns="http://www.hibernate.org/xsd/hibernate-mapping">
  <class name="some.package.Ticket" table="TICKETS" lazy="true">
    <composite-id name="ticketId">
      <key-property name="id" column="ID" type="java.lang.Long"/>
    </composite-id>
    <property name="description" column="DESCRIPTION" type="java.lang.String"/>
    <sql-insert>INSERT INTO TICKETS (DESCRIPTION) VALUES (?)</sql-insert>
  </class>
</hibernate-mapping>

但是，当我尝试保留新的Ticket时，ORM代码失败。以下代码产生org.hibernate.id.IdentifierGenerationException: null id generated for:class some.package.Ticket

try (final Session session = sessionFactory.openSession()) {
  final Ticket ticket = new Ticket("description");
  session.save(ticket);
}

有没有办法解决这个问题？

在Hibernate xml中映射包装的自动生成的主键

0 个答案: