Expose QueryLogger invocations as events

With JMX in mind, I am thinking how to expose Cayenne stack statistics to the outside observers. There are many parameters that can be monitored in Cayenne. For the purpose of this task we are limiting the scope on low level JDBC operations, such as running queries and updates, and reading result sets, i.e. a subset of what QueryLogger logs.

Suggested approach to this problem is to replace direct calls to QueryLogger from everywhere in the code to an event mechanism, with a logging listener delegating to QueryLogger (for a fully backwards compatible behavior), and an optional statistics listener that can be exposed via a JMX MBean interface. Now QueryLogger has a bunch of methods that we should not expose as events. Those we can keep calling directly. I'd like to concentrate on the following methods:

logQuery(String queryStr, List<DbAttribute> attrs, List<?> params, long time)
logSelectCount(int count, long time)
logUpdateCount(int count)
logQueryError(Throwable th)
logGeneratedKey(DbAttribute attribute, Object value)
logCommitTransaction(String transactionLabel)
logRollbackTransaction(String transactionLabel)
logQueryParameters(String label, List<DbAttribute> attrs, List<Object> parameters, boolean isInserting)

I am not entirely happy with QueryLogger API. The events may be a little more generic than what we are using for logging (but we should be able to derive current logging info from them). E.g. we can have something like this:

DataNodeListener:

• queryStarted(QueryStartEvent event)
• queryFinished(QueryFinishEvent event)

QueryStartEvent:

• Query getQuery()
• String getTranslatedQuery()
• QueryParameters getQueryParameters() // account for simple queries and batches .. may have a List<List<DbAttribute>> vs. List<List<Object>> or something like that...
• long getTimestamp()

QueryFinishEvent:

• boolean isCommitted() // true if committed false if rolled back
• Throwable getException() // for rolled back queries
• long getTimestamp() // comparing start and finish timestamps on a given thread should give a query run time
• int getSelectedRowsCount()
• int getUpdatedRowsCount()