在选中的Exception上无法清除java.sql.Statement

Question

In my method show below find bug is specifying

    public int updateSecurityCodeHistoryForMessage(String phone, String securityCodeHistoryId, String messageState, String messageId, String parentMessageId)
    {
            CaptivePortalLogger.appLog.error(MODULE+"Start : updateSecurityCodeHistoryForMessage::"+messageState);
            int result=-1;

        String query=null;
        Connection con = null;
        PreparedStatement pstmt =null;
        try
        {
            CaptivePortalLogger.sysOut.debug(MODULE + " (Method : isSecurityCodeUsed) Available Connection : "+ CaptivePortalDBConnection.getNumIdleConnections());
            CaptivePortalLogger.sysOut.debug(MODULE + " (Method : isSecurityCodeUsed) Active Connection : "+ CaptivePortalDBConnection.getNumActiveConnections() );

            con = CaptivePortalDBConnection.getDataSource().getConnection();
            CaptivePortalLogger.appLog.error(MODULE+" Before updateSecurityCodeHistoryForMessage into SendMessageAndReceiveReport: ");              

            query="UPDATE tblsecuritycodehistory SET messagestate = ?,messageid = ? WHERE securitycodehistoryid = ? AND mobileno = ?";

            CaptivePortalLogger.appLog.debug(MODULE + "for updateSecurityCodeHistoryForMessage in SendMessageAndReceiveReport Query : "+ query);

            pstmt = con.prepareStatement(query);
            pstmt.setString(1,messageState); //<b>line 556</b>
            pstmt.setString(2,messageId);
            pstmt.setString(3,securityCodeHistoryId);
            pstmt.setString(4,phone);
            result = pstmt.executeUpdate();

            CaptivePortalLogger.appLog.error(MODULE+" After updateSecurityCodeHistoryForMessage into SendMessageAndReceiveReport: result::"+result);
        }
        catch (Exception e) {
            result = -1;
            CaptivePortalLogger.traceLog.debug("Got an exception while updateSecurityCodeHistoryForMessage in SendMessageAndReceiveReport: ",e);
        }
        finally
        {
            CaptivePortalLogger.appLog.debug(MODULE+"Finally Start");
            try
            {
                if(pstmt!=null)
                    pstmt.close();
                if(con !=null)
                    con.close();

                CaptivePortalLogger.sysOut.debug(MODULE + " (Method : updateSecurityCodeHistoryForMessage) Closing connections done ....");

            }
            catch(Exception e)
            {
                CaptivePortalLogger.traceLog.debug("Error in closing sqlReader.",e);
            }
        }
    CaptivePortalLogger.appLog.error(MODULE+"End : updateSecurityCodeHistoryForMessage");
    return result;
}

I find lots of links on stack but none of them able to solve my problem(may be im not able to understand them properly). Any help will be appreciated.

Thanks in Advance..........

After updaing my finally block with a solution specfied by problem persists

finally
{
    CaptivePortalLogger.appLog.debug(MODULE+"Finally Start");
    try {
        if(pstmt!=null)
            pstmt.close();
    } catch (Exception ex) {
        // Log, ignore, etc
    }
    try {
        if(con !=null)
            con.close();
    } catch (Exception ex) {
        // Log, ignore, etc
    }
    CaptivePortalLogger.sysOut.debug(MODULE + " (Method : updateSecurityCodeHistoryForMessage) Closing connections done ....");
}

After using @Jon suggestion , my problem get resolved. finally resolved code is ::

public int updateSecurityCodeHistoryForMessage(String phone, String securityCodeHistoryId, String messageState, String messageId, String parentMessageId)
    {
            CaptivePortalLogger.appLog.error(MODULE+"Start : updateSecurityCodeHistoryForMessage::"+messageState);
            int result=-1;
            String query=null;
            Connection con = null;
            PreparedStatement pstmt =null;
            try
            {
                CaptivePortalLogger.sysOut.debug(MODULE + " (Method : isSecurityCodeUsed) Available Connection : "+ CaptivePortalDBConnection.getNumIdleConnections());
                CaptivePortalLogger.sysOut.debug(MODULE + " (Method : isSecurityCodeUsed) Active Connection : "+ CaptivePortalDBConnection.getNumActiveConnections() );

                con = CaptivePortalDBConnection.getDataSource().getConnection();
                CaptivePortalLogger.appLog.error(MODULE+" Before updateSecurityCodeHistoryForMessage into SendMessageAndReceiveReport: ");              

                query="UPDATE tblsecuritycodehistory SET messagestate = ?,messageid = ? WHERE securitycodehistoryid = ? AND mobileno = ?";

                CaptivePortalLogger.appLog.debug(MODULE + "for updateSecurityCodeHistoryForMessage in SendMessageAndReceiveReport Query : "+ query);
                try
                {
                    pstmt = con.prepareStatement(query);
                    pstmt.setString(1,messageState);
                    pstmt.setString(2,messageId);
                    pstmt.setString(3,securityCodeHistoryId);
                    pstmt.setString(4,phone);
                    result = pstmt.executeUpdate();
                }
                catch(SQLException e1)
                {
                    CaptivePortalLogger.traceLog.debug("Error in closing sqlReader.",e1);
                }
                finally{
                    if(pstmt!=null)
                    pstmt.close();
                }

                CaptivePortalLogger.appLog.error(MODULE+" After updateSecurityCodeHistoryForMessage into SendMessageAndReceiveReport: result::"+result);
            }
            catch (SQLException e2) {
                result = -1;
                CaptivePortalLogger.traceLog.debug("Got an exception while updateSecurityCodeHistoryForMessage in SendMessageAndReceiveReport: ",e2);
            }
            finally
            {
                CaptivePortalLogger.appLog.debug(MODULE+"Finally Start");
                try
                {
                    if(con !=null)
                        con.close();

                    CaptivePortalLogger.sysOut.debug(MODULE + " (Method : updateSecurityCodeHistoryForMessage) Closing connections done ....");

                }
                catch(SQLException e)
                {
                    CaptivePortalLogger.traceLog.debug("Error in closing sqlReader.",e);
                }
            }
        CaptivePortalLogger.appLog.error(MODULE+"End : updateSecurityCodeHistoryForMessage");
        return result;
    }

Answer 1

Look at this code:

if(pstmt!=null)
    pstmt.close();
if(con !=null)
    con.close();

Now consider that pstmt.close() can throw an exception... which means con.close() wouldn't be called.

If you're using Java 7, use a try-with-resources statement instead, but otherwise you should have a separate try/finally block for each resource.

try {
   connection = ...;
   try {
      statement = ...;
   } finally {
      // Clean up statement
   }
} finally {
   // Clean up connection
}

I'd also strongly recommend against catching blanket Exception - it's better to catch specific exceptions which you can actually handle, and let other exceptions propagate up the stack. Also, you appear to be using integer values to signal success or failure of your method - that's not idiomatic Java; exceptions are preferred for error handling, in general.

Answer 2

The problem is that if pstmt.close() throws an Exception, then the connection is never closed.

Either do not close the statement in the finally (as drivers are required to close Statement objects if the Connection is closed), or put both in their own try..catch -block. Eg:

finally
{
    CaptivePortalLogger.appLog.debug(MODULE+"Finally Start");
    try {
        if(pstmt!=null)
            pstmt.close();
    } catch (Exception ex) {
        // Log, ignore, etc
    }
    try {
        if(con !=null)
            con.close();
    } catch (Exception ex) {
        // Log, ignore, etc
    }
    CaptivePortalLogger.sysOut.debug(MODULE + " (Method : updateSecurityCodeHistoryForMessage) Closing connections done ....");
}

Answer 3

Firebug is correct.

You should close all your SQL resources in a finally block, using individually wrapped calls to close methods.

You can do it with a utility class:

package persistence;

public class DatabaseUtils {
    // similar methods for ResultSet and Connection
    public static void close(Statement s) {
        try {
            if (s != null) {
                s.close();
            }
        } catch (SQLException e) {
            // Log the exception
        }       
    }
} 

Call the close method in a finally block in the method that created the resource.

Answer 4

尝试在单独的try / catch / finally块中清理/关闭资源，否则如果任何一个抛出异常，则其余的将保持未闭合。