JPA - analog of LobCreator from hibernate?

Question

in pure Hibernate i can do:

Blob blob= Hibernate.getLobCreator(sessionFactory.getCurrentSession()).createBlob(inputStream, len);

How to do this in jpa (with hibernate as provider)?

In pure hibernate i made user type for blobs, which used setBinaryStream prepared statement. This solution worked for me perfectly and i'm looking for a way to port it to JPA.

Answer 1

You can use the @Lob annotation on your persistent property (Annotation Lob):

@Entity
public class MyEntity {

private byte[] content;
...

@Lob
public byte[] getContent() {
return content;
}

public void setContent(byte[] newContent) {
this.content = newContent;
}
}

In your code you can transform a stream in a byte[] with a code like this:

@Transient
public void setContentFromInputStream(InputStream is) throws IOException 
{
    ByteArrayOutputStream baos = new ByteArrayOutputStream();

    byte[] buff = new byte[1024];
    int l = 0;
    do {
        l = is.read(buff);
        if (l > 0)
        {
            baos.write(buff, 0, l);
        }
    } while (l > 0);
    
    is.close();
    baos.flush();
    baos.close();
    
    content = baos.toByteArray();
}

The @Lob annotation can also be used with String, in this case you'll obtain a CLOB on the DB

You must pay attention to the size of the byte[] to avoid OutOfMemoryError.

To use only streams you must rely on the specific jdbc vendor implementation. For example if you are using Hibernate >= 3.6 you can change they type of MyEntity.content to Blob and write:

MyEntity entity = new MyEntity();
Session session = (Session)entityManager.getDelegate(); 
Blob newContent = session.getLobHelper().createBlob(inputStream, len); 
entity.setContent(newContent);

I hope this can help you