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