Java 休眠OneToMany FetchType.EAGER不返回值

我使用Hibernate 3.5.6和MySQL 5.1。 我有3个类：Item、Attribute、AttributeValue。它们以一对多的关系相互关联，我确实获得了给定项目的所有属性。但对于给定的属性，我不会得到AttributeValue。我看不到异常或错误，表中的数据看起来不错，这意味着数据的插入进行得很顺利

我尝试了不同的策略来获取属性值映射的属性模式，但结果总是空的

我错过了什么

以下是课程：

@Entity
@Table(name = "Item")
public class Item implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private String serialNumber;

    @OneToMany(fetch = FetchType.EAGER, mappedBy = "item", cascade = CascadeType.ALL)
    @Fetch(value = FetchMode.SELECT)    // don't remove this line
    @MapKey(name = "name")
    private Map<String, Attribute> attributes = new HashMap<String, Attribute>();

    protected Item() {
        super();
    }

    public Item(String serialNumber) {
        this();
        setSerialNumber(serialNumber);
    }

    public String getSerialNumber() {
        return serialNumber;
    }

    protected void setSerialNumber(String serialNumber) {
        this.serialNumber = serialNumber;
    }

    public Map<String, Attribute> getAttributes() {
        return attributes;
    }

    public void setAttributes(Map<String, Attribute> attributes) {
        this.attributes = attributes;
    }
}

---

下面是基础表的SQL：

--
-- Table structure for table `Attribute`
--

CREATE TABLE `Attribute` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `item_serialNumber` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `item_serialNumber` (`item_serialNumber`,`name`),
  KEY `FK7839CA7C252F491C` (`item_serialNumber`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

--
-- Table structure for table `Item`
--

CREATE TABLE `Item` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `serialNumber` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `serialNumber` (`serialNumber`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

--
-- Table structure for table `AttributeValue`
--

CREATE TABLE `AttributeValue` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `value` varchar(255) DEFAULT NULL,
  `attribute_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `attribute_id` (`attribute_id`,`value`),
  KEY `FK4C1BA6C69CA0A39A` (`attribute_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Constraints for dumped tables
--

--
-- Constraints for table `Attribute`
--
ALTER TABLE `Attribute`
  ADD CONSTRAINT `FK7839CA7C252F491C` FOREIGN KEY (`item_serialNumber`) REFERENCES `Item` (`serialNumber`);

--
-- Constraints for table `AttributeValue`
--
ALTER TABLE `AttributeValue`
  ADD CONSTRAINT `FK4C1BA6C69CA0A39A` FOREIGN KEY (`attribute_id`) REFERENCES `Attribute` (`id`);

---

您已使用“值”而不是“属性”映射属性中的值。 @OneToMany注释应指定如下：

@OneToMany(fetch = FetchType.EAGER, mappedBy = "attribute", cascade = CascadeType.ALL)

---

谢谢，我真不敢相信我错过了。非常感谢。

--
-- Table structure for table `Attribute`
--

CREATE TABLE `Attribute` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `item_serialNumber` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `item_serialNumber` (`item_serialNumber`,`name`),
  KEY `FK7839CA7C252F491C` (`item_serialNumber`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

--
-- Table structure for table `Item`
--

CREATE TABLE `Item` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `serialNumber` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `serialNumber` (`serialNumber`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

--
-- Table structure for table `AttributeValue`
--

CREATE TABLE `AttributeValue` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `value` varchar(255) DEFAULT NULL,
  `attribute_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `attribute_id` (`attribute_id`,`value`),
  KEY `FK4C1BA6C69CA0A39A` (`attribute_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Constraints for dumped tables
--

--
-- Constraints for table `Attribute`
--
ALTER TABLE `Attribute`
  ADD CONSTRAINT `FK7839CA7C252F491C` FOREIGN KEY (`item_serialNumber`) REFERENCES `Item` (`serialNumber`);

--
-- Constraints for table `AttributeValue`
--
ALTER TABLE `AttributeValue`
  ADD CONSTRAINT `FK4C1BA6C69CA0A39A` FOREIGN KEY (`attribute_id`) REFERENCES `Attribute` (`id`);

@OneToMany(fetch = FetchType.EAGER, mappedBy = "attribute", cascade = CascadeType.ALL)