Writing Log Records Only After a Condition Occurs
Suppose you are trying to track down an infrequent bug on a production
system with copious amounts of debug log messages. In most cases, when
the bug occurs, it is not necessary to have the entire history of log
messages; only a recent few are needed. To minimize the impact on the
system, a MemoryHandler can be used to store a number of log records
in memory and then dump them out only if the bug or other condition
occurs.
try {
// Create a memory handler with a memory of 100 records
// and dumps the records into the file my.log when a
// SEVERE message is logged
FileHandler fhandler = new FileHandler("my.log");
int numRec = 100;
MemoryHandler mhandler = new MemoryHandler(fhandler, numRec, Level.SEVERE);
// Add to the desired logger
Logger logger = Logger.getLogger("com.mycompany");
logger.addHandler(mhandler);
} catch (IOException e) {
}
try {
// Create a memory handler with a memory of 100 records
// and dumps the records into the file my.log when a
// some abitrary condition occurs
FileHandler fhandler = new FileHandler("my.log");
int numRec = 100;
MemoryHandler mhandler = new MemoryHandler(fhandler, numRec, Level.OFF) {
public synchronized void publish(LogRecord record) {
// Log it before checking the condition
super.publish(record);
boolean condition = false;
if (condition) {
// Condition occurred so dump buffered records
push();
}
}
};
// Add to the desired logger
Logger logger = Logger.getLogger("com.mycompany");
logger.addHandler(mhandler);
} catch (IOException e) {
}
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