updateBlob()-example?

Hallo together,

maybe someone can help - i can get updateBlob() working and i couldn't find
any working example so far.

ResultSet rs...
Blob b=getBlob(1);

works just fine, but how do i store a modified value in the database?

I tried:

bytes[] bt=...;//something binary

Blob newblob=new Blob(); //does not work, Blob is not instanciateable

//writing the "Blobs" data as byte[]-Array using

rs.updateBytes(1, bt);

//fails because it modifies the contents of the byte[], or maybe i don't
//understand what this function can be used for.

Blob b=rs.getBlob(1);

// throws null-pointer for insertRow and "wrong format for integer" for
// updateRow, although row "1" is definitely an varchar-column

b.setBytes(0,bt); //could not test because of above
rs.updateBlob(b);// dito

What is the right (and efficient) way to do this?

Guido

remark: as the large-object table is named to be a "potential security leak"
as all user have the right to read from it, i like to store values for
(middle sized) objects directly in my tables.