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https://issues.apache.org/jira/browse/DERBY-5872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13419891#comment-13419891
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Bryan Pendleton commented on DERBY-5872:
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Looks quite thorough and complete. Thanks for cleaning this up; I'm always
pleased
to see patches that remove redundant code!
I'm not that familiar with java.sql.Wrapper. It is a JDBC4/JDK6 feature, is
that right?
I tried to look back through svn history to figure out when these wrapper
methods were
introduced, and it looks like it was at least 5 years ago. It's interesting
that nobody
encountered these problems until now; I suppose this means that the Wrapper
interface isn't heavily used?
Regardless, thanks again for cleaning up the implementation and adding the
extra tests.
> Inconsistency between isWrapperFor() and unwrap() in logical statements
> -----------------------------------------------------------------------
>
> Key: DERBY-5872
> URL: https://issues.apache.org/jira/browse/DERBY-5872
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.4.1.3, 10.5.1.1, 10.6.1.0, 10.7.1.1, 10.8.1.2,
> 10.9.1.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
> Attachments: derby-5872-1a.diff
>
>
> I noticed this when I refactored the logical statement classes in DERBY-5868.
> The isWrapperFor() method forwards calls to the underlying physical
> statement, but the unwrap() method works purely at the logical level.
> For example, if you produce a LogicalPreparedStatement40 instance with this
> code
> ClientConnectionPoolDataSource ds = new
> ClientConnectionPoolDataSource();
> ds.setDatabaseName("testdb");
> ds.setCreateDatabase("create");
> ds.setMaxStatements(10);
> PooledConnection pc = ds.getPooledConnection();
> Connection c = pc.getConnection();
> PreparedStatement ps = c.prepareStatement("values 1");
> you'll see that
> System.out.println(ps.isWrapperFor(LogicalPreparedStatement40.class));
> prints false, telling that ps is not a wrapper for
> LogicalPreparedStatement40. However, trying to unwrap ps as a
> LogicalPreparedStatement succeeds:
> LogicalPreparedStatement40 lps =
> ps.unwrap(LogicalPreparedStatement40.class);
> On the other hand
> System.out.println(ps.isWrapperFor(PreparedStatement40.class));
> prints true, indicating that ps is a wrapper for PreparedStatement40, but
> trying to unwrap it as one, fails:
> PreparedStatement40 ps4 = ps.unwrap(PreparedStatement40.class);
> Exception in thread "main" java.sql.SQLException: Unable to unwrap for 'class
> org.apache.derby.client.am.PreparedStatement40'
> at
> org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:108)
> at
> org.apache.derby.client.am.SqlException.getSQLException(SqlException.java:364)
> at
> org.apache.derby.client.am.LogicalStatementEntity.unwrap(LogicalStatementEntity.java:258)
> at
> org.apache.derby.client.am.LogicalPreparedStatement.unwrap(LogicalPreparedStatement.java:57)
> at Test.main(Test.java:37)
> Caused by: org.apache.derby.client.am.SqlException: Unable to unwrap for
> 'class org.apache.derby.client.am.PreparedStatement40'
> ... 3 more
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