Hibernate问题：@OneToMany注释返回重复项

Question

我在Hibernate（4.3.0）中遇到了一个问题，其中as单向@OneToMany返回重复项。

我的数据库结构（MySQL与InnoDB），其中作为“条目”表与“entry_address”表有1： N关系。“条目”表是主表，“entry_address”是“条目”表的子表。

CREATE TABLE IF NOT EXISTS `entry` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(500) NOT NULL,
  `active` int(1) NOT NULL DEFAULT '0',
  `modifiedTS` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' ON UPDATE CURRENT_TIMESTAMP,
  `createdTS` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=4 ;

INSERT INTO `entry` (`id`, `name`, `active`, `modifiedTS`, `createdTS`) VALUES
(1, 'Test1', 0, '2012-11-05 13:41:03', '2012-11-01 10:11:22'),
(2, 'Test2', 1, '2012-11-05 11:19:37', '2012-11-01 10:11:33'),
(3, 'Test3', 1, '2012-11-05 11:19:37', '2012-11-01 10:11:44');

CREATE TABLE IF NOT EXISTS `entry_address` (
  `id` int(10) unsigned NOT NULL,
  `precedence` int(1) NOT NULL DEFAULT '0',
  `line` varchar(255) DEFAULT NULL,
  `line2` varchar(255) DEFAULT NULL,
  `street` varchar(255) DEFAULT NULL,
  `street2` varchar(255) DEFAULT NULL,
  `zip` int(5) DEFAULT NULL,
  `city` varchar(255) DEFAULT NULL,
  `country` varchar(255) DEFAULT NULL,
  UNIQUE KEY `entry_address_uq` (`id`,`precedence`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `entry_address` (`id`, `precedence`, `line`, `line2`, `street`, `street2`, `zip`, `city`, `country`) VALUES
(1, 0, 'Line4.1', 'Line4.2', 'Street4.1', 'Street4.2', 9488, 'Schellenberg', 'Liechtenstein'),
(2, 10, 'Line1.1', 'Line1.2', 'Street1.1', 'Street1.2', 9492, 'Eschen', 'Liechtenstein'),
(2, 20, 'Line2.1', 'Line2.2', 'Street2.1', 'Street2.2', 9490, 'Vaduz', 'Liechtenstein'),
(2, 30, 'Line3.1', 'Line3.2', 'Street3.1', 'Street3.2', 9494, 'Schaan', 'Liechtenstein'),
(3, 10, 'Line5.1', 'Line5.2', 'Street5.1', 'Street5.2', 9492, 'Eschen', 'Liechtenstein'),
(3, 20, 'Line6.1', 'Line6.2', 'Street6.1', 'Street6.2', 9492, 'Eschen', 'Liechtenstein');

ALTER TABLE `entry_address`
  ADD CONSTRAINT `entry_address_fk` FOREIGN KEY (`id`) REFERENCES `entry` (`id`);

下面是“entry”实体的最小代码。

import java.util.Collection;
import javax.persistence.*;

@Entity
@Table(name = "entry")
public class Entry {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private Integer id;

    @Column(name = "name")
    private String name;

    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "id")
    private Collection<EntryAddress> addresses;

    @Override
    public String toString() {
        return String.format("Entry [id=%s, name=%s, addresses=%s]", id, name, addresses);
    }
}

以下是“entry_address”实体的最小代码：

import javax.persistence.*;

@Entity
@Table(name = "entry_address")
public class EntryAddress {
    @Id
    @Column(name = "id")
    private Integer id;

    @Column(name = "line")
    private String line;

    @Override
    public String toString() {
        return String.format("EntryAddress [line=%s]", line);
    }
}

这是Hibernate完成的查询（看起来不错！）：Hibernate:选择此u0.id作为id0 1 u，此0.name作为name0 1 u，addresses2 0.id作为id0 3 0，addresses2 0.id作为id1 0，addresses2 0.line作为行1 0 0，从此0.id=addresses2 0.id上的左外连接条目2 0

但如果我使用以下命令运行JUnit：

import java.util.Collection;

import junit.framework.Assert;
import li.pitschmann.transaction.dao.EntryDao;
import li.pitschmann.transaction.entity.Entry;

import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.AbstractTransactionalJUnit4SpringContextTests;

@ContextConfiguration(locations={"file:**/web-spring.xml"})
public class EntryDaoTest extends AbstractTransactionalJUnit4SpringContextTests {
    @Autowired
    private EntryDao entryDao;

    @Test
    public void findAllEntries() {
        Collection<Entry> entries = entryDao.findEntries();

        Assert.assertNotNull(entries);

        for (Entry e : entries) {
            System.out.println("++: " + e);
        }
        // Assert.assertEquals(3, entries.size());

    }
}

import java.util.Collection;

import org.hibernate.SessionFactory;
import org.springframework.transaction.annotation.Transactional;

import li.pitschmann.transaction.dao.EntryDao;
import li.pitschmann.transaction.entity.Entry;

public class EntryDaoImpl implements EntryDao {
    private SessionFactory sessionFactory;

    /**
     * {@inheritDoc}
     */
    @SuppressWarnings("unchecked")
    @Transactional
    public Collection<Entry> findEntries() {
        return sessionFactory.getCurrentSession().createCriteria(Entry.class).list();
    }

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }
}

SpringXML（最重要的部分，Spring3.1.2.RELEASE）：

<tx:annotation-driven transaction-manager="transactionManager" />
<context:annotation-config />
<!-- MySQL DataSource -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="com.mysql.jdbc.Driver" />
    <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/entry_db" />
    <property name="user" value="root" />
    <property name="password" value="" />
</bean>
<!-- Session Factory -->
<bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan">
        <list>
            <value>li.pitschmann.transaction.entity</value>
        </list>
    </property>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</prop>
            <prop key="hibernate.show_sql">true</prop>
        </props>
    </property>
</bean>
<!-- Transaction Manager -->
<bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
</bean>

控制台日志为：

++: Entry [id=1, name=Test1, addresses=[EntryAddress [line=Line4.1]]]
++: Entry [id=2, name=Test2, addresses=[EntryAddress [line=Line1.1], EntryAddress [line=Line1.1], EntryAddress [line=Line1.1]]]
++: Entry [id=2, name=Test2, addresses=[EntryAddress [line=Line1.1], EntryAddress [line=Line1.1], EntryAddress [line=Line1.1]]]
++: Entry [id=2, name=Test2, addresses=[EntryAddress [line=Line1.1], EntryAddress [line=Line1.1], EntryAddress [line=Line1.1]]]
++: Entry [id=3, name=Test3, addresses=[EntryAddress [line=Line5.1], EntryAddress [line=Line5.1]]]
++: Entry [id=3, name=Test3, addresses=[EntryAddress [line=Line5.1], EntryAddress [line=Line5.1]]]

我还尝试使用@OneToMany（fetch=FetchType.LAZY）代替FetchType.EAGER-同样的问题，地址重复。

++: Entry [id=1, name=Test1, addresses=[EntryAddress [line=Line4.1]]]
++: Entry [id=2, name=Test2, addresses=[EntryAddress [line=Line1.1], EntryAddress [line=Line1.1], EntryAddress [line=Line1.1]]]
++: Entry [id=3, name=Test3, addresses=[EntryAddress [line=Line5.1], EntryAddress [line=Line5.1]]]

预料

这是我的期望（3个不同地址的条目对象）：

++: Entry [id=1, name=Test1, addresses=[EntryAddress [line=Line4.1]]]
++: Entry [id=2, name=Test2, addresses=[EntryAddress [line=Line1.1], EntryAddress [line=Line2.1], EntryAddress [line=Line3.1]]]
++: Entry [id=3, name=Test3, addresses=[EntryAddress [line=Line5.1], EntryAddress [line=Line6.1]]]

Hibernate中是否有bug，或者我做错了什么？希望有人能帮我找到根本原因？！谢谢：-）

Answer 1

您可能需要像这样修改您的方法：

@SuppressWarnings("unchecked")
@Transactional
public Collection<Entry> findEntries() {
    return sessionFactory.getCurrentSession()
      .createCriteria(Entry.class)
      .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY)
      .list();
}

此外，将地址更改为Set：

@OneToMany(fetch=FetchType.EAGER)
@JoinColumn(name = "id")
private Set<EntryAddress> addresses;

编辑：

哦……在EntryAddress中，您将id定义为@id，但它不是唯一的。您应该将id设为主键，并使其像在Entry中一样自动递增。然后在EntryAddress中创建另一个字段，它是Entry的外键，称为Entry\u id。