问题
I'm working with JUL for my logging (no I can't change that). I've developed a simple wrapper that I pass in the parameters and it creates the FileHandler with the correct format every time so that I don't have to recreate the logging in every project.
My test app functions exactly as intended, but when I import the library into other projects I seem to be getting one (only one so far) unique error: Every single time, it adds a ".0" to the end of the log file.
It does this even when there is no conflicts and the Filehandler has been configured to append to the end an existing file (which it does fine). I've played with various file names, most recently I've been using the simple "mylog.log" and the log file still gets output as "mylog.log.0". I've checked and the fileHandler is being passed the correct file ("mylog.log"), but it isn't logging there.
This does not happen in my logging test, only in the project I actually want to use it in. Even when using the exact same parameters, I get different file names.
Is there some quirk about JUL that I'm missing? Code is very simple. Relevent code:
String logFilePath = directory+name; // directory and name are method arguments
Handler newFileHandler;
File dirFile = new File(directory);
if(!dirFile.exists())
{
dirFile.mkdirs();
}
newFileHandler = new FileHandler(logFilePath, true);
newFileHandler.setFormatter(myformatter);
//... etc
回答1:
It does this even when there is no conflicts ....
Is that proven with evidence or an assumption? According to the FileHandler documentation:
If no "%g" field has been specified and the file count is greater than one, then the generation number will be added to the end of the generated filename, after a dot.
If there is a conflict and no "%u" field has been specified, it will be added at the end of the filename after a dot. (This will be after any automatically added generation number.)
Note that the use of unique ids to avoid conflicts is only guaranteed to work reliably when using a local disk file system.
A conflict can include opening more than one FileHandler to the same location. You need to verify each of these points. What helps is adding code to grab the RuntimeMXBean and then add a single log statement to record the calling ClassLoader, current thread, runtime name and the start time. The runtime name usually maps to a process id and a host name. Run the program and verify the contents of the file.
The code you have included helps but, you need to include details on how the application is launched and what is included in the logging.properties.
回答2:
I eventually figured this out and forgot to post the cause.
Two things were at work:
Due to the environment I was in, the "rolling" logging was being activated by some back ground variables I wasn't aware of, hence why the ".0" was being added when it shouldn't have been, but I only saw it once I moved it out of testing and into the actual implementing project.
JUL is ridiculously inflexible in how it works. Really I can't speak poorly enough about it. Anyway, long story short, if rolling logging is enabled it will always append a file number such that the active log ends in ".0". Typically I've used APIs that only had the number on the secondary logs, while the current log would maintain the exact name you gave it - this caused me some trouble as JUL also has no "get current log file" method to get the name of active file, so I needed to create an ugly method that predicted what the name should be based on the parameters, and hope nothing went wrong. As an aside, you cannot change the format of the generation numbers (which also caused me some issue as it was preferred to have the files number 01, 02, ... 10, 11 rather than 0,1,2,...10).
来源：https://stackoverflow.com/questions/24048657/java-filehandler-adding-unnecessary-digit-to-file-name