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8: Events and Alarms

Applications that monitor entities--such as variables, devices, or services--must keep users informed of events involving those entities. An event is a change in an application's state reflecting a change in the state of a monitored entity. An application or its users define which kinds of state changes are events. Some examples of events are:

• Starting a print job on a monitored printer
• Updating a monitored database
• Updating a variable that counts the bytes in a file

Most events do not require a user's attention. Such events are called basic events, which applications sometimes record in an event log.

Each event that might require a user's attention is called an alarm event. Applications display alarm events to users and record those events in an event log. The circumstances that caused an alarm event are called an alarm. The alarm event itself is also commonly called an alarm. Some examples of possible alarms are:

• The failure of a print job on a monitored printer
• An unsuccessful attempt to update a monitored database
• The growth of a monitored file beyond the maximum size allowed

Alarms vary in their severity, which can range from minor to critical, and in their status, which can progress from open to fixed. Each application or its users define which kinds of events cause alarms and how serious, or severe, each alarm is.

Applications that generate events should be able to:

• Record each alarm event in a log and inform users when a new alarm event occurs
• Display alarm views (representations of one or more alarms)
• Manipulate alarm views (for example, by sorting them at a user's request)

This chapter provides guidelines for designing your application's events and alarms.

Java Look and Feel Design Guidelines: Advanced Topics. Copyright 2001. Sun Microsystems, Inc. All Rights Reserved.