Mig-infocom MiG Calendar DBConnect Guide Uživatelský manuál stáhnout pdf (Strana 20)

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pollIntervall is > 0 poll actions will be added, though

coalesced (removed) if next to each other in the queue.

Adapting to Other Databases (DBTypeAdapter)

For instance the JDBC driver for the Oracle database returns a

BigDecimal object for Integer and Long columns. Other

untested databases or JDBC drivers may have similar oddities and

the DBTypeAdapter are created to accommodate for these cases.

DBTypeAdapter is a converter that converts objects returned from

the JDBC driver into more appropriate Java object types that can be

handled by DBConnect. You install the converter on a

DBDataProvider instance.

View the DBTypeAdapter JavaDoc for details on how to use this

class.

Listening for Concurrent Update Events

Since DBConnect is using the high performance optimistic locking

algorithm there are the possibility that if data are updated from two

clients at the same time one of the updates will be lost. Optimistic

locking will identify that the data will be lost though and you can listen

for these occasions by adding a ConcurrentUpdateListener

to the DataProvider. The listener can with customizable logic

decide what to do in these cases. Re-read the data or force an update

to the database anyway, even though the data in the database has

been changed since it was last read.

View the DataProvider.addConcurrentUpdateListener

JavaDoc for details on how to do this.

Listening for Exceptions

Since DBConnect is using a background thread to communicate with

the database it is not possible to surround the actions that will lead to

a database interaction with a try-catch block. You can get the same

result by adding an ExceptionListener to the

DataSynchronizer. It will be notified if a database action resulted

in an exception, including a reference to the original exception.

If no listeners are registered with the data synchronizer the exception

will be dumped to System.err.

View the DataSynchronizer.addExceptionListener

JavaDoc for details on how to do this.

Note that if a DataAction (for instance a poll or save) is retired

more than retryCount number of times it will be put back first in

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Mig-infocom MiG Calendar DBConnect Guide Uživatelský manuál Strana 20