Determine file being used by FileHandler

Question

I am creating a java.util.logging.FileHandler that is allowed to cycle through files. When multiple instances of my application are run, a new log file is created for each instance of the application. I need to know what file is being used by the application because I want to upload the log file to my servers for further review. How can I tell what file is being used by a certain FileHandler?

Answer 1

The easiest way is to put some kind of identifier in the file name itself, i.e. the pattern argument when you create the FileHandler. Since these are instances of the same application, one way to distinguish them is by their process id, so you could make that part of the pattern. A better approach is to pass in an identifier through the command line and use that to make your filename. That way you control the files being created in some sense. Finally, if your application has some knowledge of why it's different from all the others, for example it connects to a particular database server, then you could just use that database server name as part of the filename.

EDIT: There does not seem to be any API to get the name of the file being used by a FileHandler. I would suggest looking into the logging extensions in x4juli (which ports a lot of the log4j functionality to the java.util.logging specs):

• http://www.x4juli.org/

You should be able to substitute an instance of their FileHandler which provides a getFile() method:

• http://www.x4juli.org/api/org/x4juli/handlers/FileHandler.html

Answer 2

Actually, you could do this much simpler by simply extending FileHandler yourself. For example...

MyFileHandler.java:

import java.io.IOException;
import java.util.logging.FileHandler;
public class MyFileHandler extends FileHandler {
    protected String _MyFileHandler_Patern;
    public MyFileHandler(String pattern) throws IOException {
        _MyFileHandler_Patern = pattern;
    }
    public String getMyFileHandlerPattern() {
        return _MyFileHandler_Patern;
    }
}

DeleteMe.java:

import java.io.IOException;
import java.util.logging.Handler;
import java.util.logging.Logger;
public class DeleteMe {
    public static void main(String[] args) throws IOException {
        Logger log = Logger.getLogger(DeleteMe.class.getName());
        MyFileHandler output = new MyFileHandler("output.log");
        log.addHandler(output);
        for (Handler handler : log.getHandlers()) {
            if (handler instanceof MyFileHandler) {
                MyFileHandler x = (MyFileHandler) handler;
                if ("output.log".equals(x.getMyFileHandlerPattern())) {
                    System.out.println("found hanlder writing to output.log");
                }
            }
        }
    }
}