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https://issues.apache.org/jira/browse/DERBY-5872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13419788#comment-13419788
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Knut Anders Hatlen commented on DERBY-5872:
-------------------------------------------
The other implementations of isWrapperFor() and unwrap() in the logical classes
(LogicalConnection40 and LogicalDatabaseMetaData40) work strictly at the
logical level. That is, their unwrap() methods behave the same way as in the
statement classes, but their isWrapperFor() methods don't. In those classes,
isWrapperFor() returns true if and only if unwrap() would succeed, and unwrap()
succeeds if and only if the instance implements/extends the specified
interface/class. I think we should change the statement classes to behave the
same way.
> 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
>
> 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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