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https://issues.apache.org/jira/browse/DERBY-5090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13058608#comment-13058608
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Knut Anders Hatlen commented on DERBY-5090:
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I had a look at the 1a patch and it looks like a good fix. I was a bit
surprised by the use of MessageId.CONN_ALREADY_CLOSED to tell that the stream
was closed, but after checking messages.xml, I found that the message text
wasn't connection-specific despite the name of the constant.
One tiny nit in EmbedResultSet:
- currentStream = stream;
+ // Wrap in a stream throwing exception on invocations when closed.
+ currentStream = stream = new CloseFilterInputStream(stream);
return stream;
Perhaps avoiding the double assignment would be slightly clearer:
currentStream = new CloseFilterInputStream(stream);
return currentStream;
?
Before the fix, the stream sometimes worked (or perhaps it just appeared to
work?) after reading the next column, whereas now it'll always throw an
IOException. Should we mention that in the release notes?
> Retrieving BLOB fields sometimes fails
> --------------------------------------
>
> Key: DERBY-5090
> URL: https://issues.apache.org/jira/browse/DERBY-5090
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.7.1.1
> Environment: JDBC derby embedded driver
> Reporter: Unai Vivi
> Assignee: Kristian Waagan
> Labels: BLOB, exception, null, read
> Attachments: Derby5090.java, Derby5090_2.java, Derby5090_3.java,
> derby-5090-1a-fix.diff, derby-5090-1a-fix.stat, derby-5090-2a-test.diff,
> derby-5090-2a-test.stat
>
>
> 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
> [...]
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