Using java.util.logging (default)

The default implementation of java.util.logging provided in the JDK is too limited to be useful. A limitation of JDK Logging appears to be the inability to have per-web application logging, as the configuration is per-VM. As a result, Tomcat will, in the default configuration, replace the default LogManager implementation with a container friendly implementation called JULI, which addresses these shortcomings. It supports the same configuration mechanisms as the standard JDK java.util.logging, using either a programmatic approach, or properties files. The main difference is that per-classloader properties files can be set (which enables easy redeployment friendly webapp configuration), and the properties files support slightly extended constructs which allows more freedom for defining handlers and assigning them to loggers.

JULI is enabled by default, and supports per classloader configuration, in addition to the regular global java.util.logging configuration. This means that logging can be configured at the following layers:

• That is usually done in the ${catalina.base}/conf/logging.properties file. The file is specified by the java.util.logging.config.file System property which is set by the startup scripts. If it is not readable or is not configured, the default is to use the ${java.home}/lib/logging.properties file in the JRE.

• In the web application. The file will be WEB-INF/classes/logging.properties

The default logging.properties in the JRE specifies a ConsoleHandler that routes logging to System.err. The default conf/logging.properties in Apache Tomcat also adds several FileHandlers that write to files.

A handler’s log level threshold is INFO by default and can be set using SEVERE, WARNING, INFO, CONFIG, FINE, FINER, FINEST or ALL. You can also target specific packages to collect logging from and specify a level.

Here is how you would set debugging from Tomcat. You would need to ensure the ConsoleHandler’s (or FileHandler’s’) level is also set to collect this threshold, so FINEST or ALL should be set. Please refer tojava.util.logging documentation in the JDK for the complete details:

org.apache.catalina.level=FINEST

The configuration used by JULI is extremely similar to the one supported by plain java.util.logging, but uses a few extensions to allow better flexibility in assigning loggers. The main differences are:

• A prefix may be added to handler names, so that multiple handlers of a single class may be instantiated. A prefix is a String which starts with a digit, and ends with ‘.’. For example, 22foobar. is a valid prefix.
• System property replacement is performed for property values which contain ${systemPropertyName}.
• As in Java 6, loggers can define a list of handlers using the loggerName.handlers property.
• By default, loggers will not delegate to their parent if they have associated handlers. This may be changed per logger using the loggerName.useParentHandlers property, which accepts a boolean value.
• The root logger can define its set of handlers using the .handlers property.

There are several additional implementation classes, that can be used together with the ones provided by Java. The notable one is org.apache.juli.FileHandler.

org.apache.juli.FileHandler supports buffering of the logs. The buffering is not enabled by default. To configure it, use the bufferSize property of a handler. The value of 0 uses system default buffering (typically an 8K buffer will be used). A value of <0 forces a writer flush upon each log write. A value >0 uses a BufferedOutputStream with the defined value but note that the system default buffering will also be applied.

Example logging.properties file to be placed in $CATALINA_BASE/conf:

handlers = 1catalina.org.apache.juli.FileHandler, \

2localhost.org.apache.juli.FileHandler, \

3manager.org.apache.juli.FileHandler, \

java.util.logging.ConsoleHandler

 

.handlers = 1catalina.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler

 

############################################################

# Handler specific properties.

# Describes specific configuration info for Handlers.

############################################################

 

1catalina.org.apache.juli.FileHandler.level = FINE

1catalina.org.apache.juli.FileHandler.directory = ${catalina.base}/logs

1catalina.org.apache.juli.FileHandler.prefix = catalina.

 

2localhost.org.apache.juli.FileHandler.level = FINE

2localhost.org.apache.juli.FileHandler.directory = ${catalina.base}/logs

2localhost.org.apache.juli.FileHandler.prefix = localhost.

 

3manager.org.apache.juli.FileHandler.level = FINE

3manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs

3manager.org.apache.juli.FileHandler.prefix = manager.

3manager.org.apache.juli.FileHandler.bufferSize = 16384

 

java.util.logging.ConsoleHandler.level = FINE

java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

 

 

############################################################

# Facility specific properties.

# Provides extra control for each logger.

############################################################

 

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = \

2localhost.org.apache.juli.FileHandler

 

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = INFO

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = \

3manager.org.apache.juli.FileHandler

 

# For example, set the org.apache.catalina.util.LifecycleBase logger to log

# each component that extends LifecycleBase changing state:

#org.apache.catalina.util.LifecycleBase.level = FINE

Example logging.properties for the servlet-examples web application to be placed in WEB-INF/classes inside the web application:

handlers = org.apache.juli.FileHandler, java.util.logging.ConsoleHandler

 

############################################################

# Handler specific properties.

# Describes specific configuration info for Handlers.

############################################################

 

org.apache.juli.FileHandler.level = FINE

org.apache.juli.FileHandler.directory = ${catalina.base}/logs

org.apache.juli.FileHandler.prefix = servlet-examples.

 

java.util.logging.ConsoleHandler.level = FINE

java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter

Documentation references

• Apache Tomcat Javadoc for the org.apache.juli package.
• Oracle Java 6 Javadoc for the java.util.logging package.

Considerations for productive usage

You may want to take note of the following:

• Consider removing ConsoleHandler from configuration.
• By default (thanks to the .handlers setting) logging goes both to a FileHandler and to aConsoleHandler. The output of the latter one is usually captured into a file, such as catalina.out. Thus you end up with two copies of the same messages.
• Consider removing FileHandlers for the applications that you do not use. E.g., the one for host-manager.
• The handlers by default use the system default encoding to write the log files. It can be configured with encoding property.
• Consider configuring an Access log.