My concern is that it seems too low-level, accessing DataNode
directly (hence you have to manage connection state and all that).
But there is another more fundamental problem of a Blob becoming
invalid when the connection that generated it is closed.
So I wonder if instead of mapping a column directly as a Blob, we
should implement our own mapping primitive (BlobHolder?), that can re-
read the Blob as many times as requested. The other piece is a
callback interface that is provided with the regular Blob instance
guaranteed to be in the valid state (i.e. inside a Cayenne
transaction). A callback can read the stream, and do whatever with it
(like pushing data to HttpResponse):
interface (or class) BlobHolder {
void readBlob(BlobCallback callback);
}
interface BlobCallback {
// this is called within transaction span and the Blob is
guaranteed to be valid
void blobRead(Blob);
}
We can use a BlobFault similar to what you wrote as a way to
initialize BlobHolder with an object qualifier (so that it knows how
to fetch itself).
What do you think?
Andrus
On Nov 20, 2006, at 6:21 PM, Tore Halset (JIRA) wrote:
[ http://issues.apache.org/cayenne/browse/CAY-316?page=all ]
Tore Halset updated CAY-316:
----------------------------
Attachment: BlobFaultType.java
stream support for blob/clob
----------------------------
Key: CAY-316
URL: http://issues.apache.org/cayenne/browse/CAY-316
Project: Cayenne
Type: New Feature
Components: Cayenne Core Library
Versions: 1.2 [STABLE]
Reporter: Tore Halset
Assignee: Andrus Adamchik
Priority: Minor
Fix For: UNDEFINED FUTURE
Attachments: BlobFault.java, BlobFaultType.java
It would be nice if cayenne would support for streaming blob/clob.
It should at least be possible to prevent caching of blobs.
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