我有一张正在使用的旧表，如下所示：
+------------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+--------------+------+-----+---------+-------+
| BINARY_DATA_ID | varchar(255) | NO | PRI | | |
| BINARY_DATA | longblob | YES | | NULL | |
| BINARY_DATA_NAME | varchar(255) | YES | | NULL | |
+------------------+--------------+------+-----+---------+-------+
这样做的主要问题是BinaryDataJava 类会加载BINARY_DATA列，即使我只需要BINARY_DATA_NAME. 我知道构建此架构的最佳方法是将数据从元数据（如文件名）中拆分出来，以便它们存在于单独的表中。从那里开始，使数据延迟加载是微不足道的。这就是它应该首先完成的方式。
不幸的是，由于组织限制，我可能无法执行上述操作。作为一种解决方法，是否可以使用一些注释使该列延迟加载，而不是将内容拆分到单独的表中？我已经修改了这个BinaryData类，使它有一个内部静态BinaryDataData类，它@Embedded的属性是@Basic(fetch=FetchType.LAZY)：
@Entity
@Table
@Proxy(lazy=false)
@Inheritance(strategy=InheritanceType.JOINED)
public class BinaryData implements Serializable, Persistable<BinaryData>, Cloneable {
private static final long serialVersionUID = /** blah */;
@Id @Column @GeneratedValue(generator="uuid") @GenericGenerator(name="uuid", strategy="uuid")
private String id;
@Column
private String binaryDataName;
@Embedded
@Basic(fetch = FetchType.LAZY)
private BinaryDataData binaryData;
@Transient
private String cacheId;
/**
* Hibernate constructor
*/
public BinaryData() { /* Creates a new instance of Attachment. */}
public BinaryData(byte[] binaryData, String binaryDataName) {
this.binaryData = new BinaryDataData(ArrayUtils.clone(binaryData));
this.binaryDataName = binaryDataName;
}
/**
* Returns the BinaryData byte stream.
*
* @return binaryData byte stream
*/
@Embedded
@Basic(fetch = FetchType.LAZY)
public byte[] getBinaryData() {
if (this.binaryData == null) {
return new byte[0];
}
return binaryData.getActualData();
}
@Embeddable
public static class BinaryDataData implements Serializable {
@Column(length=32*1024*1024, columnDefinition="longblob", name="BINARY_DATA") @Lob
private byte[] actualData;
public BinaryDataData() { }
public BinaryDataData(byte[] data) {
this.actualData = data;
}
public byte[] getActualData() {
if (this.actualData == null) {
return new byte[0];
}
return this.actualData;
}
public void setBinaryData(byte[] newData) {
this.actualData = newData;
}
@Override public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (!(obj instanceof BinaryDataData)) {
return false;
}
final BinaryDataData other = (BinaryDataData) obj;
if (!Arrays.equals(actualData, other.actualData)) {
return false;
}
return true;
}
}
/** onwards... */
不幸的是，这不起作用。即使未请求二进制数据，我看到的 SQL 仍然显示对象的完整获取：
select ideaattach0_.BINARY_DATA_ID as BINARY1_9_, ideaattach0_1_.BINARY_DATA as BINARY2_9_, ideaattach0_1_.BINARY_DATA_NAME as BINARY3_9_, ideaattach0_.IDEA_BUCKET_ID as IDEA2_136_ from IDEA_ATTACHMENT ideaattach0_ inner join BINARY_DATA ideaattach0_1_ on ideaattach0_.BINARY_DATA_ID=ideaattach0_1_.BINARY_DATA_ID where ideaattach0_.BINARY_DATA_ID=?
有任何想法吗？谢谢你。