[DERBY-5090] Retrieving BLOB fields sometimes fails

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.7.1.1
• Fix Version/s: 10.9.1.0
• Component/s: JDBC
• Labels: BLOB derby_backport_reject_10_8 exception null read
• Environment: JDBC derby embedded driver
• Urgency: Low
• Issue & fix info: Newcomer, Release Note Needed, Repro attached, Workaround attached
• Bug behavior facts: Embedded/Client difference
• Assignee: Kristian Waagan
• Reporter: Unai Vivi
• Created: 03/Mar/11 16:51
• Updated: 17/Jun/13 09:19
• Resolved: 18/Aug/11 07:29

Description

This is my first issue report, so please be understanding if I'm posting the wrong thing, in the wrong place or in the wrong way. I just want to help.

While iterating through a ResultSet, when accessing a BLOB field to read its contents via an InputStream, I noticed that:

• if the current ResultSet's has been "warmed up" by retrieving another column first, everything it's fine;
• if, on the other hand, you first-thing access the BLOB (and read other columns later), then upon reading the first byte out the InputStream bound to the BLOB field (ResultSet.getBinaryStream("col_name")) an IOException is thrown (and IOException's getMessage() method returns null).

Following is an example, taken from a real application. The two code segments only differ in the fact that a SMALLINT & VARCHAR read is done before/after the BLOB read.

-Working snippet-
[...]
icRelPath[i] = "imm" + File.separator + "ic" + "" + rs.getShort("setIcone") + "" + i + "." + rs.getString("estensione");
AutoCloseInputStream acis = new AutoCloseInputStream(rs.getBinaryStream("ic" + i));
if (rs.wasNull())
icRelPath[i] = null;
else
{
//icRelPath[i] = "imm" + File.separator + "ic" + "" + rs.getShort("setIcone") + "" + i + "." + rs.getString("estensione");
BufferedInputStream bis = new BufferedInputStream(acis);
int b = bis.read();//READS FINE
[...]

-Broken snippet-
[...]
//icRelPath[i] = "imm" + File.separator + "ic" + "" + rs.getShort("setIcone") + "" + i + "." + rs.getString("estensione");
AutoCloseInputStream acis = new AutoCloseInputStream(rs.getBinaryStream("ic" + i));
if (rs.wasNull())
icRelPath[i] = null;
else
{
icRelPath[i] = "imm" + File.separator + "ic" + "" + rs.getShort("setIcone") + "" + i + "." + rs.getString("estensione");
BufferedInputStream bis = new BufferedInputStream(acis);
int b = bis.read();//THROWS IOException WITH A null ERROR MESSAGE STRING
[...]

Issue Links

• incorporates: DERBY-4521 Stream passed out to user does not heed close, allowing reads after next ResultSet#getXXX