org.imixs.workflow.engine

Class EventLogService

java.lang.Object

org.imixs.workflow.engine.EventLogService

public class EventLogService
extends Object

The EventLogService is a service to create and access an event log .

An event that occurs during an update or a processing function within a transaction becomes a fact when the transaction completes successfully. The EventLogService can be used to store this kind of "Change Data Capture" events in a log. An example is the LuceneUpdateService, which should update the index of a document only if the document was successfully written to the database.

The service is bound to the current PersistenceContext and stores a EventLog entity directly in the database to represent an event. These types of events can be queried by clients through the service.

The EventLogService provides a lock/unlock mechanism. An eventLog entry can optional be locked for processing. The topic of the event will be suffixed with '.lock' to indicate that this topic is locked by a running process. If a lock is successful a client can exclusive process this eventLog entry.

The method releaseDeadLocks unlocks eventlog entries which are older than 1 minute. We assume that these events are deadlocks.

Version:

1.0

Author:

rsoika

See Also:

EventLog, UpdateService

Field Summary

Fields

Modifier and Type	Field and Description
static String	EVENTLOG_LOCK_DATE

Constructor Summary

Constructors

Constructor and Description
EventLogService()

Method Summary

Modifier and Type	Method and Description
EventLog	createEvent(String topic, String refID) Creates/updates a new event log entry.
EventLog	createEvent(String topic, String refID, Calendar timeout) Creates/updates a new event log entry.
EventLog	createEvent(String topic, String refID, ItemCollection document) Creates/updates a new event log entry.
EventLog	createEvent(String topic, String refID, ItemCollection document, Calendar timeout) Creates/updates a new event log entry.
EventLog	createEvent(String topic, String refID, Map<String,List<Object>> data, Calendar timeout) Creates/updates a new event log entry.
List<EventLog>	findAllEvents(int firstResult, int maxResult) Returns all event log entries
List<EventLog>	findEventsByRef(int maxCount, String ref, String... topic) Finds events for one or many given topics assigned to a given document reference ($uniqueId).
List<EventLog>	findEventsByTimeout(int maxCount, String... topic) Finds events for one or many given topics within the current timeout.
List<EventLog>	findEventsByTopic(int maxCount, String... topic) Finds events for one or many given topics
EventLog	getEvent(String id) Returns an detached event log entry by its ID.
boolean	lock(EventLog _eventLogEntry) This method locks an eventLog entry for processing.
void	releaseDeadLocks(long deadLockInterval, String... topic) This method unlocks eventlog entries which are older than 1 minute.
void	removeEvent(EventLog _eventLog) Deletes an existing eventLog.
void	removeEvent(String id) Deletes an existing eventLog by its id.
boolean	unlock(EventLog _eventLogEntry) This method unlocks an eventLog entry.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EVENTLOG_LOCK_DATE

public static final String EVENTLOG_LOCK_DATE

See Also:

Constant Field Values

Constructor Detail

EventLogService

public EventLogService()

Method Detail

createEvent

public EventLog createEvent(String topic,
                            String refID)

Creates/updates a new event log entry.

Parameters:

refID - - uniqueid of the document to be assigned to the event

topic - - the topic of the event.

Returns:

- generated event log entry

createEvent

public EventLog createEvent(String topic,
                            String refID,
                            Calendar timeout)

Creates/updates a new event log entry.

Parameters:

refID - - uniqueid of the document to be assigned to the event

topic - - the topic of the event.

timeout - - optional timeout calendar object

Returns:

- generated event log entry

createEvent

public EventLog createEvent(String topic,
                            String refID,
                            ItemCollection document)

Creates/updates a new event log entry.

Parameters:

refID - - uniqueId of the document to be assigned to the event

topic - - the topic of the event.

document - - optional document providing a data map

Returns:

- generated event log entry

createEvent

public EventLog createEvent(String topic,
                            String refID,
                            ItemCollection document,
                            Calendar timeout)

Creates/updates a new event log entry.

Parameters:

refID - - uniqueId of the document to be assigned to the event

topic - - the topic of the event.

document - - optional document providing a data map

timeout - - optional timeout calendar object

Returns:

- generated event log entry

createEvent

public EventLog createEvent(String topic,
                            String refID,
                            Map<String,List<Object>> data,
                            Calendar timeout)

Creates/updates a new event log entry.

Parameters:

refID - - uniqueId of the document to be assigned to the event

topic - - the topic of the event.

data - - optional data map

Returns:

- generated event log entry

findEventsByTopic

public List<EventLog> findEventsByTopic(int maxCount,
                                        String... topic)

Finds events for one or many given topics

Parameters:

maxCount - - maximum count of events to be returned

topic - - list of topics

Returns:

- list of eventLogEntries

findEventsByTimeout

public List<EventLog> findEventsByTimeout(int maxCount,
                                          String... topic)

Finds events for one or many given topics within the current timeout.

The attribte 'timeout' is optional. If the timeout is set to a future point of time, the event will be ignored by this method.

Parameters:

maxCount - - maximum count of events to be returned

topic - - list of topics

Returns:

- list of eventLogEntries

findEventsByRef

public List<EventLog> findEventsByRef(int maxCount,
                                      String ref,
                                      String... topic)

Finds events for one or many given topics assigned to a given document reference ($uniqueId). The method returns an empty list if no event log entries exist of the given refId,

Parameters:

maxCount - - maximum count of events to be returned

ref - - a reference ID for an assigned Document or Workitem instance

topic - - list of topics

Returns:

- list of eventLogEntries

findAllEvents

public List<EventLog> findAllEvents(int firstResult,
                                    int maxResult)

Returns all event log entries

Parameters:

firstResult - - first result

maxResult - - maximum count of events to be returned

Returns:

- list of eventLogEntries

removeEvent

public void removeEvent(EventLog _eventLog)

Deletes an existing eventLog. The method catches javax.persistence.OptimisticLockException as this may occur during parallel requests.

Parameters:

eventLog -

removeEvent

public void removeEvent(String id)

Deletes an existing eventLog by its id. The method catches javax.persistence.OptimisticLockException as this may occur during parallel requests.

Parameters:

eventLog -

getEvent

public EventLog getEvent(String id)

Returns an detached event log entry by its ID.

Parameters:

id - - id of the eventLog Entry

Returns:

detached eventLog entry or null if not found

lock

public boolean lock(EventLog _eventLogEntry)

This method locks an eventLog entry for processing. The topic will be suffixed with '.lock' to indicate that this topic is locked by a process. If a lock is successful a client can exclusive process this eventLog entry.

The method adds a item 'eventlog.lock.date' with a timestamp. This timestamp is used by the method 'autoUnlock' to release locked entries.

Parameters:

eventLogEntry -

Returns:

- true if lock was successful

unlock

public boolean unlock(EventLog _eventLogEntry)

This method unlocks an eventLog entry. The topic suffix '.lock' will be removed.

Parameters:

eventLogEntry -

Returns:

- true if unlock was successful

releaseDeadLocks

public void releaseDeadLocks(long deadLockInterval,
                             String... topic)

This method unlocks eventlog entries which are older than 1 minute. We assume that these events are deadlocks.