我正在尝试将文档作为BLOB存储在我拥有的java域对象中。
我看过几篇帖子说可以使用@Lob来完成
http://www.java2s.com/Tutorial/Java/0355__JPA/MarkByteArrayFieldAsLob.htm
所以，我遇到的问题是，当我存储数据时似乎都很好，我可以在我的mysql数据库中看到它，但是当我尝试在域对象中找到它时，它总是为空。
有什么想法吗？
注意，我在我的实体中使用的相关getter和setter如下：
@Lob
public byte[] getData() {
return data;
}
public void setData(byte[] data) {
this.data = data;
}
更新根据Pascal Thivent的评论，我添加了一些代码。我也简化了测试。如果我有一个实体对象，有两个字段，一个id和数据，例如
@Entity
@Table(name = "picture")
public class Picture extends BaseObject{
Long id;
byte[] data;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Lob
public byte[] getData() {
return data;
}
public void setData(byte[] data) {
this.data = data;
}
}
现在，创建和保存数据没有问题。但是，当我尝试通过调用标准
来检索数据时 this.entityManager.find(clazz, id);
填充了Picture.class和相关的id，我得到以下异常。
注意异常中一条非常有趣的行，我认为关键是：
CausedBy: mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column "test@email.com"
请注意，“test@email.com”是我放入数据字段的字节数组的值，因此就好像sql正在查找列名，这实际上是字节数组的名称内容。怪异！
javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.model.Picture#2]
at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:630)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:195)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:198)
at $Proxy28.find(Unknown Source)
at com.service.impl.BaseManagerImpl.get(BaseManagerImpl.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy32.get(Unknown Source)
at com.service.UserManagerTest.testSaveOrUpdatePicture(UserManagerTest.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: org.hibernate.exception.SQLGrammarException: could not load an entity: [com.model.Picture#2]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1874)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:48)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:42)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3044)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:395)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:375)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:139)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:195)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:103)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:878)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:815)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:808)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:175)
... 35 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'test@email.com' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1031)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:957)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3376)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3308)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2543)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1737)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1888)
at com.mysql.jdbc.BlobFromLocator.length(BlobFromLocator.java:334)
at org.hibernate.type.ByteArrayBlobType.get(ByteArrayBlobType.java:89)
at org.hibernate.type.AbstractLobType.nullSafeGet(AbstractLobType.java:46)
at org.hibernate.type.AbstractType.hydrate(AbstractType.java:81)
at org.hibernate.persister.entity.AbstractEntityPersister.hydrate(AbstractEntityPersister.java:2096)
at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:1380)
at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:1308)
at org.hibernate.loader.Loader.getRow(Loader.java:1206)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:580)
at org.hibernate.loader.Loader.doQuery(Loader.java:701)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1860)
... 47 more
根据Pascal的请求生成的SQL是：
休眠：选择picture0_.id为id32_0_，picture0_.data为data32_0_ from picture picture0_ where picture0_.id =？
答案 0 :(得分：2)
尝试设置blob的获取类型。 JPA标准表示它应默认为急切加载，但Hibernate曾经与规范有一些细微差别，因此您可以尝试以下
@Lob
@Basic(fetch = FetchType.EAGER)
public byte[] getData() {
return data;
}
答案 1 :(得分：0)
对你来说可能有点晚，但其他人可能会受益。
我有一个类似的问题并通过删除属性'？emulateLocators = true'来解决它我在我的jdbc-URL上（我之前需要它来处理其他错误）。
jpa / hibernate上可能存在一个允许它与模拟定位器一起使用的属性，但我没有查看它。
答案 2 :(得分：0)
同样对于后代，设置FetchType.EAGER对我没有帮助，但是删除emulateLocators = true确实有帮助。