Chapter 12. Logging using java.util.logging

Table of Contents

Overview

The PostgreSQL JDBC Driver supports the use of logging (or tracing) to help resolve issues with the PgJDBC Driver when is used in your application.

The PgJDBC Driver uses the logging APIs of java.util.logging that is part of Java since JDK 1.4, which makes it a good choice for the driver since it don't add any external dependency for a logging framework. java.util.logging is a very rich and powerful tool, it's beyond the scope of this docs to explain or use it full potential, for that please refer to Java Logging Overview.

This logging support was added since version 42.0.0 of the PgJDBC Driver, and previous versions uses a custom mechanism to enable logging that it is replaced by the use of java.util.logging in current versions, the old mechanism is no longer available.

Please note that while most people asked the use of a Logging Framework for a long time, this support is mainly to debug the driver itself and not for general sql query debug.

Configuration

The Logging APIs offer both static and dynamic configuration control. Static control enables field service staff to set up a particular configuration and then re-launch the application with the new logging settings. Dynamic control allows for updates to the logging configuration within a currently running program.

As part of the support of a logging framework in the PgJDBC Driver, there was a need to facilitate the enabling of the Logger using connection properties, which uses a static control to enable the tracing in the driver. Keep in mind that if you use an Application Server (Tomcat, JBoss, WildFly, etc.) you should use the facilities provided by them to enable the logging, as most Application Servers use dynamic configuration control which makes easy to enable/disable logging at runtime.

The root logger used by the PgJDBC driver is org.postgresql.

Enable logging by using connection properties

The driver provides a facility to enable logging using connection properties, it's not as feature rich as using a logging.properties file, so it should be used when you are really debugging the driver.

The properties are loggerLevel and loggerFile:

loggerLevel: Logger level of the driver. Allowed values: OFF, DEBUG or TRACE.

This option enable the java.util.logging.Logger Level of the driver based on the following mapping:

loggerLevel java.util.logging
OFF OFF
DEBUG FINE
TRACE FINEST

As noted, there are no other levels supported using this method, and internally the driver Logger levels should not (for the most part) use others levels as the intention is to debug the driver and don't interfere with higher levels when some applications enable them globally.

loggerFile: File name output of the Logger.

If set, the Logger will use a java.util.logging.FileHandler to write to a specified file. If the parameter is not set or the file can't be created the java.util.logging.ConsoleHandler will be used instead.

This parameter should be use together with loggerLevel.

The following is an example of how to use connection properties to enable logging:

jdbc:postgresql://localhost:5432/mydb?loggerLevel=DEBUG
jdbc:postgresql://localhost:5432/mydb?loggerLevel=TRACE&loggerFile=pgjdbc.log

Enable logging by using logging.properties file

The default Java logging framework stores its configuration in a file called logging.properties. Settings are stored per line using a dot notation format. Java installs a global configuration file in the lib folder of the Java installation directory, although you can use a separate configuration file by specifying the java.util.logging.config.file property when starting a Java program. logging.properties files can also be created and stored with individual projects.

The following is an example of setting that you can make in the logging.properties:

# Specify the handler, the handlers will be installed during VM startup.
handlers= java.util.logging.FileHandler

# Default global logging level.
.level= OFF

# default file output is in user's home directory.
java.util.logging.FileHandler.pattern = %h/pgjdbc%u.log
java.util.logging.FileHandler.limit = 5000000
java.util.logging.FileHandler.count = 20
java.util.logging.FileHandler.formatter = java.util.logging.SimpleFormatter
java.util.logging.FileHandler.level = FINEST

java.util.logging.SimpleFormatter.format=%1$tY-%1$tm-%1$td %1$tH:%1$tM:%1$tS %4$s %2$s %5$s%6$s%n

# Facility specific properties.
org.postgresql.level=FINEST

And when you run your application you pass the system property: java -jar -Djava.util.logging.config.file=logging.properties run.jar

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