Building upon Andreas' answer, I can think of a couple of approaches to the issue of only performing the formatting if the Logger.isDebugEnabled returns true:
Option 1: Pass in a "do formatting" flag
One option is to have a method argument that tells whether or not to actually perform the formatting. A use case could be:
System.out.println(lazyFormat(true, "Hello, %s.", "Bob"));
System.out.println(lazyFormat(false, "Hello, %s.", "Dave"));
Where the output would be:
Hello, Bob.
null
The code for lazyFormat is:
private String lazyFormat(boolean format, final String s, final Object... o) {
if (format) {
return String.format(s, o);
}
else {
return null;
}
}
In this case, the String.format is only executed when the format flag is set to true, and if it is set to false it will return a null. This would stop the formatting of the logging message to occur and will just send some "dummy" info.
So a use case with the logger could be:
logger.debug(lazyFormat(logger.isDebugEnabled(), "Message: %s", someValue));
This method doesn't exactly fit the formatting that is asked for in the question.
Option 2: Check the Logger
Another approach is to ask the logger directly if it isDebugEnabled:
private static String lazyFormat(final String s, final Object... o) {
if (logger.isDebugEnabled()) {
return String.format(s, o);
}
else {
return null;
}
}
In this approach, it is expected that logger will be visible in the lazyFormat method. And the benefit of this approach is that the caller will not need to be checking the isDebugEnabled method when lazyFormat is called, so the typical use can be:
logger.debug(lazyFormat("Debug message is %s", someMessage));
