Hibernate - Out of memory inserting big blob

问题:

In POJO i have:

public void setBlob(InputStream in, Long l) {
        this.blob = Hibernate.getLobCreator(SessionFactoryHelper.sessionFactory.getCurrentSession()).createBlob(in, l);
}

I made hibernate.jdbc.use_streams_for_binary true in config, but does it really change something?

when saving entity, on session.flush() i get:

   org.hibernate.engine.jdbc.batch.internal.AbstractBatchImpl release
INFO: HHH000010: On release of batch it still contained JDBC statements
Exception in thread "AWT-EventQueue-0" java.lang.OutOfMemoryError: Java heap space
Heap dump file created [46180174 bytes in 1.662 secs]
    at java.util.Arrays.copyOf(Arrays.java:2271)
    at java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:113)
    at java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:93)
    at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:140)
    at org.hibernate.type.descriptor.java.DataHelper.extractBytes(DataHelper.java:171)
    at org.hibernate.type.descriptor.java.BlobTypeDescriptor.unwrap(BlobTypeDescriptor.java:121)
    at org.hibernate.type.descriptor.java.BlobTypeDescriptor.unwrap(BlobTypeDescriptor.java:45)
    at org.hibernate.type.descriptor.sql.BlobTypeDescriptor$4$1.doBind(BlobTypeDescriptor.java:105)
    at org.hibernate.type.descriptor.sql.BasicBinder.bind(BasicBinder.java:92)
    at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:305)
    at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:300)
    at org.hibernate.type.AbstractSingleColumnStandardBasicType.nullSafeSet(AbstractSingleColumnStandardBasicType.java:57)
    at org.hibernate.persister.entity.AbstractEntityPersister.dehydrate(AbstractEntityPersister.java:2599)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2853)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3291)
    at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:88)
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:362)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:354)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:275)
    at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:326)
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:52)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1127)

Hibernate 4.1. Why hibernate unwrapping stream to bytea? How can i make hibernate to use prepared statement setBinaryStream? Really need help on this.

回答1:

I believe that the problem is that your in-memory object still has it's byte array populated. This is a separate issue from whether or not a stream is used to persist it to the database.

I suggest a work-around: don't store the blob in the POJO. Store the blob separately, either in the database via straight JDBC, or on disk, and then just keep a reference to the blob in your POJO (either the database primary key or the disk path/filename).

Then, when you need the blob back, get the reference from the POJO and use stream-based methods to get it back.

It's more work to get / save the blob every time that you need to, but if the blob is too large for memory, you may not have any other choice.

回答2:

I dont know why it's not working and it it should, but that what i have done to save blob to database using Hibernate:

in POJO mapped to a table:

    private byte[] serializedDocx; // + getter and setter

in a method:

    ...
     SessionFactory mf = ...
     sess = mf.openSession();
     //open connection
     sess.beginTransaction();
    ...
      ByteArrayOutputStream docxBos = new ByteArrayOutputStream();
      [write to docxBos]
      someEntity.setDocx(docxBos.toByteArray());
      sess.save(someEntity);

in myEntity.hbm.xml

  <property name="serializedDocx" type="binary">
      <column name="serialized_docx" not-null="true"/>
    </property>

in MySQL:

CREATE TABLE IF NOT EXISTS `docx` (
  `serialized_docx` longblob NOT NULL, ...

HTH.