如何在 Hibernate 中通过 Java Map 返回名称、值对（使用映射文件）

Question

我正在尝试在 Hibernate 中创建一个名称、值对，它作为 Java Map 返回。但我只得到地图中返回的 1 行。我还没有找到像这样的简单地图的任何非常清晰的例子，我看不出我做错了什么。

由于环境受限，我无法运行 hbm2dll 生成表，所以我手动生成了它，那里可能有错误。

这是我的父表和子表：

mysql> select * from zoomProperties;
+----+---------------+
| id | entityVersion |
+----+---------------+
|  1 |             0 | 
+----+---------------+
1 row in set (0.00 sec)

mysql> select * from zoomProperty;
+----+-------+-------+----------------------+
| id | name  | value | parentZoomProperties |
+----+-------+-------+----------------------+
|  1 | prop1 | val1  |                    1 | 
|  2 | prop2 | val2  |                    1 | 
|  3 | prop3 | val3  |                    1 | 
+----+-------+-------+----------------------+
3 rows in set (0.00 sec)

但我只得到一个值：

2010-12-28 16:45:58,437 ERROR [STDERR] setProperties with:
2010-12-28 16:45:58,453 ERROR [STDERR]  Key: prop1
2010-12-28 16:45:58,453 DEBUG [com.mycompany.zoom] Query returns 1 ZoomProperties
2010-12-28 16:45:58,453 ERROR [STDERR] getProperties returning:
2010-12-28 16:45:58,454 ERROR [STDERR]  Key: prop1
2010-12-28 16:45:58,454 DEBUG [com.mycompany.zoom] Key: prop1, Value: val1
2010-12-28 16:45:58,454 DEBUG [com.mycompany.zoom] ZoomProperies returned 1 properties

这是我的休眠查询：

List resultList = em.createQuery("from ZoomProperties").getResultList();
log.debug("Query returns " + resultList.size() + " ZoomProperties");

这是我的映射文件：

<hibernate-mapping>
  <class name="com.mycompany.zoom.domain.ZoomProperties" table="zoomProperties">
    <id name="id">
      <generator class="increment"/>
    </id>
    <version name="entityVersion"/>

    <map name="properties" table="zoomProperty">
      <key column="id"/>
      <map-key column="name" type="string"/>
      <element column="value" type="string"/>
    </map>
  </class>
</hibernate-mapping>

还有我的pojo：

package com.mycompany.zoom.domain;

import java.util.HashMap;
import java.util.Map;

public class ZoomProperties
{
    private Long id;
    private Map<String, String> properties = new HashMap<String, String>();
    private Integer entityVersion;

    public ZoomProperties() {}

    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }

    public Map<String, String> getProperties() //{ return properties; }
    {
        System.err.println("getProperties returning:");
        java.util.Set<String> propertyKeySet = properties.keySet();
        for (String key : propertyKeySet)
        {
            System.err.println("\tKey: " + key);
        }
        return properties;
    }
    public void setProperties(Map<String, String> properties) //{ this.properties = properties; }
    {
        this.properties = properties;
        System.err.println("setProperties with:");
        java.util.Set<String> propertyKeySet = properties.keySet();
        for (String key : propertyKeySet)
        {
            System.err.println("\tKey: " + key);
        }
    }

    public Integer getEntityVersion() { return entityVersion; }
    public void setEntityVersion(Integer entityVersion) { this.entityVersion = entityVersion; }

    public boolean equals(Object other) {
        if (other == this)
        {
            return true;
        }
        if (other instanceof ZoomProperties)
        {
            return true;
        }
        return false;
    }

    public int hashCode() {
        return "This is the one and only ZoomProperties".hashCode();
    }
}

还有我的表创建信息：

mysql> show create table zoomProperties;
+----------------+---------------------------------+
| Table          | Create Table                    |
+--------------------------------------------------+
| zoomProperties | CREATE TABLE `zoomProperties` (
  `id` bigint(20) NOT NULL auto_increment,
  `entityVersion` int(11) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1             | 
+----------------+---------------------------------+
1 row in set (0.00 sec)

mysql> show create table zoomProperty;
+--------------+-----------------------------------+
| Table        | Create Table                      |
+--------------+-----------------------------------+
| zoomProperty | CREATE TABLE `zoomProperty` (
  `id` bigint(20) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `value` varchar(255) default NULL,
  `parentZoomProperties` bigint(20) default NULL,
  PRIMARY KEY  (`id`),
  KEY `parentZoomProperties` (`parentZoomProperties`),
  CONSTRAINT `zoomProperty_ibfk_1` 
    FOREIGN KEY (`parentZoomProperties`) 
    REFERENCES `zoomProperties` (`id`) 
    ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1             | 
+--------------+-----------------------------------+
1 row in set (0.00 sec)

Answer 1

<map>里面的<key>元素是指外键，所以应该是

<map name="properties" table="zoomProperty">
    <key column="parentZoomProperties"/>
    <map-key column="name" type="string"/>
    <element column="value" type="string"/>
</map>

zoomProperty 表中的id 根本不需要。