Your analysis is correct and reverting the change will correct the problem.
I don't know why Rodney committed this change but we better make sure we don't break anything if we undo the change.
JUnit tests are needed to show the error and prove the correctness of the solution.
Anyway please create a bugzilla issue to track the problem.
-- Dirk
Simon Matic Langford wrote:
Hi,
I've recently upgraded to the latest version of Tomcat (4.1.29), which includes DBCP 1.1, over 1.0 in previous versions.
On starting my application and attempting to logon to it, it falls over with a NullPointerException, included here: java.lang.NullPointerException at oracle.jdbc.driver.ScrollableResultSet.close(ScrollableResultSet.java:14 9) at org.apache.commons.dbcp.DelegatingResultSet.close(DelegatingResultSet.ja va:193) at org.apache.commons.dbcp.DelegatingResultSet.close(DelegatingResultSet.ja va:193) at org.apache.commons.dbcp.DelegatingPreparedStatement.passivate(Delegating PreparedStatement.java:298) at org.apache.commons.dbcp.DelegatingPreparedStatement.close(DelegatingPrep aredStatement.java:185) at com.pcmsgroup.v21.star.framework.persistence.BaseDbDAO.releaseResources( BaseDbDAO.java:205) at com.pcmsgroup.v21.star.persistence.logon.LogonDbDAO.fetchByLogonName(Log onDbDAO.java:149) at com.pcmsgroup.v21.star.domain.logon.Logon.logon(Logon.java:95) at com.pcmsgroup.v21.star.service.logon.LogonService.logon(LogonService.jav a:52) at com.pcmsgroup.v21.star.application.logon.LogonCtrl.process(LogonCtrl.jav a:87) at com.pcmsgroup.v21.star.framework.application.BaseCtrl.execute(BaseCtrl.j ava:180) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestPr ocessor.java:484) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java: 274) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525) at javax.servlet.http.HttpServlet.service(HttpServlet.java:760) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Applica tionFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilt erChain.java:193) at com.pcmsgroup.v21.star.application.logon.LogonFilter.doFilter(LogonFilte r.java:168) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Applica tionFilterChain.java:213) ...
I've looked around the web, and in your CVS, and think that this is a bug.
The code in com.pcmsgroup.v21.star.framework.persistence.BaseDbDAO.releaseResources is as follows:
public final void releaseResources(Connection connection, PreparedStatement ps, ResultSet rs) throws PersistenceException { try { if (rs != null) { rs.close(); } if (ps != null) { ps.close(); } if (connection != null) { // get the Factory ConnectionFactory factory = ConnectionFactory.getInstance(); // turn the Connection back to pool factory.releaseConnection(connection); } } catch (SQLException sqle) { thisLog.error("Failed to release resources", sqle); } catch (Exception e) { thisLog.error("Failed to release resources", e); throw new PersistenceException(e); } }
As you can see, we close ResultSet, PreparedStatement and Connection in
the reverse order of that which we
got them in. On DBCP 1.0, this used to work fine. According to the JDK
API docs: "When a Statement object is closed, its current ResultSet object, if one exists, is also closed."
Thus closing the statement after closing the
result set is safe.
However, for DBCP 1.1, a change was made to DelegatingPreparedStatement
(version 1.6 to 1.7), to "ensure PreparedStatment can only be closed once", which entailed changing:
public void close() throws SQLException { passivate(); _stmt.close(); }
to:
public void close() throws SQLException { _stmt.close(); passivate(); }
I believe this has introduced my problem and is a bug. As now, following the logic:
- The statement is closed, and in accordance with the JDK docs, the result set is closed. - The passivate method is then called, which calls ResultSet.close on the underlying result set, regardless of whether it has been closed already. - This causes the underlying result set, which is already closed to try to close again, thus the NullPointer.
I couldn't spot this in the bug reports, so could someone answer if this
is a bug or not, or is there
something I am doing wrong, or should this be directed at the developers
list? I don't believe I should quietly catch Exception's in the close() methods as per your examples,
as I'd really like to know if there are problems!
Thanks
Simon
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