Custom Log Configuration

The various logging systems can be activated by including the appropriate libraries on the classpath and can be further customized by providing a suitable configuration file in the root of the classpath or in a location specified by the following Spring Environment property: logging.config.

You can force Spring Boot to use a particular logging system by using the org.springframework.boot.logging.LoggingSystem system property. The value should be the fully qualified class name of a LoggingSystem implementation. You can also disable Spring Boot’s logging configuration entirely by using a value of none.

Since logging is initialized before the ApplicationContext is created, it is not possible to control logging from @PropertySources in Spring @Configuration files. The only way to change the logging system or disable it entirely is through System properties.

Depending on your logging system, the following files are loaded:

Logging System Customization

Logback

logback-spring.xml, logback-spring.groovy, logback.xml, or logback.groovy

Log4j2

log4j2-spring.xml or log4j2.xml

JDK (Java Util Logging)

logging.properties
When possible, we recommend that you use the -spring variants for your logging configuration (for example, logback-spring.xml rather than logback.xml). If you use standard configuration locations, Spring cannot completely control log initialization.
There are known classloading issues with Java Util Logging that cause problems when running from an 'executable jar'. We recommend that you avoid it when running from an 'executable jar' if at all possible.

To help with the customization, some other properties are transferred from the Spring Environment to System properties, as described in the following table:

Spring Environment System Property Comments

logging.exception-conversion-word

LOG_EXCEPTION_CONVERSION_WORD

The conversion word used when logging exceptions.

logging.file.name

LOG_FILE

If defined, it is used in the default log configuration.

logging.file.path

LOG_PATH

If defined, it is used in the default log configuration.

logging.pattern.console

CONSOLE_LOG_PATTERN

The log pattern to use on the console (stdout).

logging.pattern.dateformat

LOG_DATEFORMAT_PATTERN

Appender pattern for log date format.

logging.charset.console

CONSOLE_LOG_CHARSET

The charset to use for console logging.

logging.threshold.console

CONSOLE_LOG_THRESHOLD

The log level threshold to use for console logging.

logging.pattern.file

FILE_LOG_PATTERN

The log pattern to use in a file (if LOG_FILE is enabled).

logging.charset.file

FILE_LOG_CHARSET

The charset to use for file logging (if LOG_FILE is enabled).

logging.threshold.file

FILE_LOG_THRESHOLD

The log level threshold to use for file logging.

logging.pattern.level

LOG_LEVEL_PATTERN

The format to use when rendering the log level (default %5p).

PID

PID

The current process ID (discovered if possible and when not already defined as an OS environment variable).

If you use Logback, the following properties are also transferred:

Spring Environment System Property Comments

logging.logback.rollingpolicy.file-name-pattern

LOGBACK_ROLLINGPOLICY_FILE_NAME_PATTERN

Pattern for rolled-over log file names (default ${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz).

logging.logback.rollingpolicy.clean-history-on-start

LOGBACK_ROLLINGPOLICY_CLEAN_HISTORY_ON_START

Whether to clean the archive log files on startup.

logging.logback.rollingpolicy.max-file-size

LOGBACK_ROLLINGPOLICY_MAX_FILE_SIZE

Maximum log file size.

logging.logback.rollingpolicy.total-size-cap

LOGBACK_ROLLINGPOLICY_TOTAL_SIZE_CAP

Total size of log backups to be kept.

logging.logback.rollingpolicy.max-history

LOGBACK_ROLLINGPOLICY_MAX_HISTORY

Maximum number of archive log files to keep.

All the supported logging systems can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples:

If you want to use a placeholder in a logging property, you should use Spring Boot’s syntax and not the syntax of the underlying framework. Notably, if you use Logback, you should use : as the delimiter between a property name and its default value and not use :-.

You can add MDC and other ad-hoc content to log lines by overriding only the LOG_LEVEL_PATTERN (or logging.pattern.level with Logback). For example, if you use logging.pattern.level=user:%X{user} %5p, then the default log format contains an MDC entry for "user", if it exists, as shown in the following example.

2019-08-30 12:30:04.031 user:someone INFO 22174 --- [  nio-8080-exec-0] demo.Controller
Handling authenticated request