java 使用 Hibernate 在 MySQL 中存储字节数组
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Store byte array in MySQL with Hibernate
提问by user2957378
I'm trying to save an entity with a byte array field. I'm using Hibernate and JPA on top of a MySQL database. This is the field definiton, which worked fine for an embedded H2 database:
我正在尝试使用字节数组字段保存实体。我在 MySQL 数据库之上使用 Hibernate 和 JPA。这是字段定义，它适用于嵌入式 H2 数据库：
@Entity(name = "blob")
public class Blob {
...
@Lob
@Basic(fetch = FetchType.LAZY)
@Column(name = "blobImg", nullable = false)
private byte[] blobImg;
}
Now, with MySQL database, an exception is thrown everytime I execute blobRepository.save(). Actually, is may be thrown when Hibernate tries to autocreate the table of Blob entity. The exception is the following:
现在，对于 MySQL 数据库，每次执行 blobRepository.save() 时都会抛出异常。实际上，当 Hibernate 尝试自动创建 Blob 实体表时可能会抛出 is 。例外情况如下：
o.h.engine.jdbc.spi.SqlExceptionHelper : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'blob (blobCols, blobImg, blobRows, channel, idBlobPersistence) values (50, _bina' at line 1
ohengine.jdbc.spi.SqlExceptionHelper ：您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，了解在“blob (blobCols、blobImg、blobRows、channel、idBlobPersistence)”值（第 1 行的 50、_bina）附近使用的正确语法
I've tried to change the field definition with several approaches I've found on the web:
我尝试使用我在网上找到的几种方法来更改字段定义：
Approach 1:
方法一：
@Column(name = "blobImg", nullable = false, columnDefinition = "BINARY(256)", length = 256)
private byte[] blobImg;
Approach 2:
方法二：
@Lob
@Column(name="blobImg", columnDefinition="bytea")
private byte[] blobImg;
Approach 3: Defining an hibernate mapping on blob.hbm.xml file and refering it from entityManagerFactory bean:
方法 3：在 blob.hbm.xml 文件上定义休眠映射并从 entityManagerFactory bean 中引用它：
<?xml version='1.0' encoding='UTF-8'?>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="mappingResources">
<list>
<value>blob.hbm.xml</value>
</list>
</property>
</bean>
blob.hbm.xml mapping:
blob.hbm.xml 映射：
<hibernate-mapping>
<class name="guiatv.persistence.domain.Blob" table="blob">
<property name="blobImgProperty">
<column name="blobImg" sql-type="binary"></column>
</property>
</class>
</hibernate-mapping>
Approach 4: changing blob.hbm.xml mapping to the following:
方法 4：将 blob.hbm.xml 映射更改为以下内容：
<?xml version='1.0' encoding='UTF-8'?>
<hibernate-mapping>
<class name="guiatv.persistence.domain.Blob" table="blob">
<property name="blobImg" type="binary">
<column name="blobImg" />
</property>
</class>
</hibernate-mapping>
All of them are throwing the same exception.
所有这些都抛出相同的异常。
How can I solve it? Thank you!
我该如何解决？谢谢！
采纳答案by user2957378
Well,
好，
I have tried your suggestions @Ernusc. The first one:
我已经尝试过你的建议@Ernusc。第一个：
@Lob(type = LobType.BLOB)
private byte[] blobImg;
it is no compiling for me. It may be my Hibernate version is different as yours. About the second option:
这对我来说不是编译。可能是我的 Hibernate 版本与您的不同。关于第二个选项：
@Type(type = "org.hibernate.type.BlobType")
@Lob
private byte[] blobImg;
It does compile, but it fails at runtime. It was showing the following error:
它可以编译，但在运行时失败。它显示以下错误：
2015-09-14 23:21:01.324 WARN 7436 --- [bTaskExecutor-3] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL Error: 1064, SQLState: 42000
2015-09-14 23:21:01.324 ERROR 7436 --- [bTaskExecutor-3] o.h.engine.jdbc.spi.SqlExceptionHelper : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'blob blob0_ where blob0_.idBlobPersistence=326' at line 1
2015-09-14 23:21:01.337 INFO 7436 --- [bTaskExecutor-3] o.h.e.internal.DefaultLoadEventListener : HHH000327: Error performing load command : org.hibernate.exception.SQLGrammarException: could not extract ResultSet
Also, when I tried to follow the trace, I found it was actually throwing the following exception:
此外，当我尝试跟踪跟踪时，我发现它实际上抛出了以下异常：
java.lang.ClassCastException: [B cannot be cast to java.sql.Blob
Then I realized the first of the error messages was actually caused by my stupid idea of naming my entity as "blob", which is probably a reserved keyword in Hibernate. So I changed the entity declaration from:
然后我意识到第一条错误消息实际上是由我将实体命名为“blob”的愚蠢想法引起的，这可能是 Hibernate 中的保留关键字。所以我改变了实体声明：
@Entity(name = "blob")
public class Blob {
...
}
to:
到：
@Entity(name = "blobframe")
public class Blob {
...
}
Then, your second suggestion was only throwing that ClassCastException exception. However, some of the approaches I tried before do work now. For instance:
然后，您的第二个建议只是抛出 ClassCastException 异常。但是，我之前尝试过的一些方法现在确实有效。例如：
@Column(name = "blobImg", nullable = false, columnDefinition = "BINARY(256)", length = 256)
private byte[] blobImg;
UPDATE:This approach is NOT working for me. It fails on blobframe table creation with the following field definition (don't know the reason, though):
更新：这种方法对我不起作用。它在使用以下字段定义创建 blobframe 表时失败（虽然不知道原因）：
@Lob
@Column(name="blobImg", columnDefinition="bytea")
private byte[] blobImg;
Thank you Ernusc for your quick response.
感谢 Ernusc 的快速回复。
回答by Ernusc
If you want to convert your byte[]to sql type Blob, you can do the following:
如果要将您的转换byte[]为 sql 类型Blob，您可以执行以下操作：
@Lob(type = LobType.BLOB)
or
或者
@Type(type = "org.hibernate.type.BlobType")
@Lob
Hope it helps
希望能帮助到你
