[DERBY-5872] Inconsistency between isWrapperFor() and unwrap() in logical statements

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.4.1.3, 10.5.1.1, 10.6.1.0, 10.7.1.1, 10.8.1.2, 10.9.1.0
• Fix Version/s: 10.10.1.1
• Component/s: JDBC
• Labels: derby_backport_reject_10_9
• Assignee: Knut Anders Hatlen
• Reporter: Knut Anders Hatlen
• Created: 21/Jul/12 09:16
• Updated: 29/Jul/13 18:58
• Resolved: 23/Jul/12 07:10

Description

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