Hook: Define New Loggable Event

Requirement

A new type of event/object needs to be logged.

Method of Adaptation

Augment feature

Level of Support

Parameter Pattern

HotSpot

Log management

Participants

Loggable, NewLoggable , LogEntry, NewLogEntry , logEntry

Changes

1. implementation NewLoggable of Loggable.
2. NewLoggable.getLogData implements Loggable.getLogData :
1. subclass NewLogEntry of LogEntry.
2. NewLogEntry.toString overrides LogEntry.toString .
3. instance logEntry of NewLogEntry.
4. fill logEntry with information to be logged.
5. return logEntry.

Constraints

• The instance of NewLogEntry must be created afresh in every call to getLogData .
• logEntry must neither explicitly nor implicitly (which is often a problem with inner classes!) hold a reference to any part of the application. The information stored in logEntry must be created just for the purpose of logging. Otherwise, it may happen that the entire application's state is stored with the entry, which will start up a second copy of the Shop when the entry is loaded for inspection.

Comments

• If an instance of NewLoggable is passed to the log.Log.log method, its getLogData method gets called.
• To inspect the contents of a log file, invoke the Inspect A Log File's contents hook.
• It is often useful, to implement the log entry as an inner class. Inner classes must be used with great care, however, because they tend to have too many implicit references.