Java Logging - where is my log file?

Question

I'm having trouble finding my log files.

I'm using Java Logging - java.util.logging - in Eclipse 3.7.1 on Windows XP. The relevant lines of my logging.properties file are:

handlers= java.util.logging.FileHandler, java.util.logging.ConsoleHandler .level=INFO java.util.logging.FileHandler.pattern = %h/java%u.log java.util.logging.FileHandler.limit = 50000 java.util.logging.FileHandler.count = 1 java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter 

As far as I can figure out, after I execute these two lines:

Logger logger = Logger.getLogger("test");  logger.logp(Level.INFO, "myClass", "myMethod", "Alcatraz");  

my log file should be in C:\Documents and Settings\[My Windows ID]\javaX.log where X is an integer.

I have 5 different java.log files in that directory, java0.log through java4.log, but none of them contain my log record or even a record with today's date on it. I did some googling and found Tracing and Logging which implies that my logs should be at a different location, c:\Documents and Settings\[My Windows ID]\Application Data\Sun\Java\Deployment\log. There is one file there, named plugin5581819941091650582.log, but it is essentially empty:

<?xml version="1.0" encoding="windows-1252" standalone="no"?> <!DOCTYPE log SYSTEM "logger.dtd"> <log> </log> 

Its creation date is last week. (I'm not sure what process created it; I certainly didn't create it explicitly.)

So where is my log file then? I can't think of anywhere else to look.

Also, does anyone know when changes to logging.properties take effect? If I changed the log level or the FileHandler.pattern, what would have to happen before my program saw the changes? Simply saving the changes in logging.properties is clearly not enough. Will I need to restart Eclipse? Or reboot the computer? Just curious. That's not nearly as big a deal to me as finding out where my log file actually is.

Answer 1

Location of log file can be control through logging.properties file. And it can be passed as JVM parameter ex : java -Djava.util.logging.config.file=/scratch/user/config/logging.properties

Details: https://docs.oracle.com/cd/E23549_01/doc.1111/e14568/handler.htm

Configuring the File handler

To send logs to a file, add FileHandler to the handlers property in the logging.properties file. This will enable file logging globally.

handlers= java.util.logging.FileHandler 

Configure the handler by setting the following properties:

java.util.logging.FileHandler.pattern=<home directory>/logs/oaam.log java.util.logging.FileHandler.limit=50000 java.util.logging.FileHandler.count=1 java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter 

java.util.logging.FileHandler.pattern specifies the location and pattern of the output file. The default setting is your home directory.

java.util.logging.FileHandler.limit specifies, in bytes, the maximum amount that the logger writes to any one file.

java.util.logging.FileHandler.count specifies how many output files to cycle through.

java.util.logging.FileHandler.formatter specifies the java.util.logging formatter class that the file handler class uses to format the log messages. SimpleFormatter writes brief "human-readable" summaries of log records.

To instruct java to use this configuration file instead of $JDK_HOME/jre/lib/logging.properties:

java -Djava.util.logging.config.file=/scratch/user/config/logging.properties 

Answer 2

Where is your logging.properties file located? It should be available in the root of the classpath. As a sanity check, what does the following code print?

System.out.println(getClass().getClassLoader().getResource("logging.properties")); 

If the code is in a static context, use

System.out.println(ClassName.class.getClassLoader().getResource("logging.properties"));