[dbcp] PoolableConnection.close() won't allow multiple close

Sun's javadoc for java.sql.Connection.close() specifies that calling close on an
already closed Connection is a no-op. However, PoolableConnection.close() (v
1.10) throws a SQLException if close() is called on a closed Connection.
PoolableConnection.close() should just return if the Connection is already
closed. Here is a patch:

To demonstrate the bug, just obtain an open PoolableConnection and call close()
on it twice; the second call will produce a SQLException. According to Sun's
spec, the second close() should just be a no-op. The current behaviour is
preferable to the old behaviour where it returned the Connection to the pool
twice, but it's still not according to the spec.

Here's a patch:

• • • PoolableConnection.java.orig 2003-09-15 16:07:53.000000000 -0400
    • PoolableConnection.java 2003-09-15 16:08:11.000000000 -0400
      ***************
    • 108,114 ****
      */
      public synchronized void close() throws SQLException {
      if(isClosed()) { ! throw new SQLException("Already closed."); }

      else {
      try {
      _pool.returnObject(this);

    • 108,114 ----
      */
      public synchronized void close() throws SQLException {
      if(isClosed()) { ! return; }

      else {
      try {
      _pool.returnObject(this);