休眠-具有多个实体的一个表?

问题描述

我有一个Picture:

public class Picture implements java.io.Serializable {

    private byte[] picEncoded;
    private String Name;
    //etc

是否可以将byte[]移至另一个类，而无需在db中创建物理上分离的表?我需要使用一些继承策略吗?

Is it's possible to move byte[] to another class without creating physically separated table in db? Do i need to use some inheritance strategy?

修改

单独实体中的Blob:

Blob in separate entity:

pojo :

 public class PictureBlob implements java.io.Serializable {
        private Integer pictureBlobId;
        private byte[] blob;

hbm::

<class name="PictureBlob" table="PICTURE">

<id name="pictureBlobId" type="int">
  <column length="200" name="PictureID"/>
</id>

<property name="blob" type="byte[]" insert="false" update="false">
  <column name="PicEncoded" not-null="false"/>
</property>
</class>

图片:

hbm::

  <one-to-one class="PictureBlob" constrained="true" name="pictureBlob" fetch="select"/>

如何插入新图片?

PictureBlob pictureBlob= new PictureBlob();
        pictureBlob.setBlob(new byte[]{84,32,22});
        Picture p = new Picture();
        p.setPictureBlob(pictureBlob);
        session.save(p);

插入记录，其中blob值为null.

inserts record where blob value is null.

推荐答案

使用组件映射在Picture和PictureBlob之间创建构图关系.示例:

Use component mapping which creates a composition relation between Picture and PictureBlob. Example:

<hibernate-mapping>
 <class name="Picture" table="PICTURE">
  <id name="pictureId" type="int">
   <generator class="native" />
  </id>
 <component name="pictureBlob " class="PictureBlob" lazy="no-proxy">
  <property name="pictureBlobId" column="PictureID" type="int" length="200" />
  <property name="blob" type="byte[]" insert="false" update="false"column="PicEncoded"/>
 </component>
 </class>
</hibernate-mapping>

POJO

public class Picture implements java.io.Serializable {
 private int pictureId;
 private PictureBlob pictureBlob;

 //Setters & Getters
}

public class PictureBlob implements java.io.Serializable {
 private int pictureBlobId;
 private byte[] blob;

 //Setters & Getters
}

也请注意:

在单值关联上使用lazy="no-proxy"以启用惰性 无需使用代理即可进行获取.需要字节码检测 注入拦截代码.

Use lazy="no-proxy" on single-valued associations to enable lazy fetching without the use of a proxy. Requires bytecode instrumentation for the injection of interception code.

在集合上使用lazy="extra"来实现智能"集合行为，即 一些收集操作，例如size(), contains(), get(),等. 不触发集合初始化.这仅是非常明智的 大量收藏.

Use lazy="extra" on collections for "smart" collection behavior, i.e. some collection operations such as size(), contains(), get(), etc. do not trigger collection initialization. This is only sensible for very large collections.

有关详细信息，请参见此处.关于获取策略

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