How to create and write a BLOB using ImmediateAccess

Question

Hi there,
I'd like to write a BLOB using ScrollableRowSetAccess an ImmediateAccess and thereby want to avoid the use of any SQL-statements.
The problem is that I can't write to an empty BLOB, so that I have to create a dummy-Blob using BLOBDomain and overwrite it afterwards (see code below).
It should be possible to avoid the creation of a dummy-BLOB but I don't know how. Could you please send me a corrected version of my code?
Thanks in advance
write File with filename to the column with index col /(or the column with name colname, if specified) of the table that is specified by ResultSetInfo rsi
public static void writeFileToBlob(int col, String colname, ResultSetInfo rsi, String filename, SessionInfo _sessionInfo)
FileInputStream fin;
Object obj;
ScrollableRowsetAccess srsa= _rsi.getRowsetAccess();
ImmediateAccess ia;
byte []mybytes;
BlobDomain
BLOB blob;
OutputStream out;
byte []myBuffer;
int bytesRead=0;
try{
//open file
fin = new FileInputStream(_filename);
//lock Row
srsa.lockRow();
if (_colname==null)
ia = (ImmediateAccess)srsa.getColumnItem(_col);
else
ia = (ImmediateAccess)srsa.getColumnItem(_colname);
obj= ia.getValueAsObject();
//insert a dummy-BLOB of size 1-byte
mybytes= new byte[1];
blobDom= new BlobDomain();
blobDom.setBytes(mybytes); //ein Byte in den BLOB schreiben
ia.setValue(blobDom); //Wert in Zeile einf|gen
//commit Data
_sessionInfo.getApplicationModule().getTransaction().commit();
//access previously created dummy-Blob
srsa.lockRow();
if (_colname==null)
ia = (ImmediateAccess)srsa.getColumnItem(_col);
else
ia = (ImmediateAccess)srsa.getColumnItem(_colname);
obj= ia.getValueAsObject();
//assign the BLOB
blob= (BLOB) obj;
//open BLOB for writing
out= blob.getBinaryOutputStream();
myBuffer= new byte[10*1024];
//read file and write the BLOB
while ((bytesRead= fin.read(myBuffer)) !=-1)
out.write(myBuffer, 0, bytesRead);
out.flush();
out.close();
fin.close();
ia.setValue(blob);
//commmit data
_sessionInfo.getApplicationModule().getTransaction().commit();
}catch(Exception e){System.out.println("writeblob:"+e);}
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Answer 1

Here are the issues with your usage of BlobDomain:
1. Streaming support is not implemented in 3.2 version of BlobDomain. It'll be implemented in our next release.
2. Your casting of object returned from getColumnItem is illegal as the objects will be of type BlobDomain and not BLOB.
3. When you create an empty BlobDomain you're in-effect meaning to call the empty_blob() method on the sql-row to create a empty blob locator.
4. You need to use getBytes(), setBytes() to read data out/set data into a blob/clob domain object in JDev 3.2
5. Casting/using oracle.sql.BLOB may lead to non-portable code (you're binding to the jdbc objects which may not be available in all tiers of deployment).
Here's the pseudocode you could use for new blobs.
1. create a new instance of BlobDomain()
2. setBytes() with actual data read from a stream. (Yes this may not work with real large blobs but we've tested blobs ~2MB in size and for larger needs, we're implementing the streaming support scheduled for our next release).
3. set the domain object into an attribute.
4. post/commit your data.
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