Learn spring boot logging configuration via application.yml file in simple and easy to follow instructions. In the default structure of a Spring Boot web application, you can locate the application.yml file under the resources folder.
Table of Contents Understand default spring boot logging Set logging level Set logging pattern Set logging output to file Using active profiles to load environment specific logging configuration Color-coded logging output
Understand default spring boot logging
To understand default spring boot logging, lets put logs in spring boot hello world example. Just to mention, there is no logging related configuration in application.yml file. If you see any configuration in downloaded application, please remove it.
private
final
Logger LOGGER = LoggerFactory.getLogger(
this
.getClass());
@RequestMapping
(
"/"
)
public
String home(Map<String, Object> model) {
LOGGER.debug(
"This is a debug message"
);
LOGGER.info(
"This is an info message"
);
LOGGER.warn(
"This is a warn message"
);
LOGGER.error(
"This is an error message"
);
model.put(
"message"
,
"HowToDoInJava Reader !!"
);
return
"index"
;
}
|
Start the application. Access application at browser and verify log messages in console.
2017
-
03
-
02
23
:
33
:
51.318
INFO
3060
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : info log statement printed
2017
-
03
-
02
23
:
33
:
51.319
WARN
3060
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : warn log statement printed
2017
-
03
-
02
23
:
33
:
51.319
ERROR
3060
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : error log statement printed
|
Note down the observation that Default logging level is INFO – because debug log message is not present.
There is fixed default log message pattern which is configured in different base configuration files.
%clr{%d{yyyy-MM-dd HH:mm:ss.SSS}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{${sys:PID}}{magenta}
%clr{---}{faint} %clr{[%
15
.15t]}{faint} %clr{%-
40
.40c{
1
.}}{cyan}
%clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}
|
The above pattern print these listed log message parts with respective color coding applied:
- Date and Time — Millisecond precision.
- Log Level — ERROR, WARN, INFO, DEBUG or TRACE.
- Process ID.
- A — separator to distinguish the start of actual log messages.
- Thread name — Enclosed in square brackets (may be truncated for console output).
- Logger name — This is usually the source class name (often abbreviated).
- The log message
Set logging level
When a message is logged via a Logger it is logged with a certain log level. In the application.yml file, you can define log levels of Spring Boot loggers, application loggers, Hibernate loggers, Thymeleaf loggers, and more. To set the logging level for any logger, add keys starting with logging.level.
Logging level can be one of one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF. The root logger can be configured using logging.level.root.
logging:
level:
root: ERROR
org.springframework.web: ERROR
com.howtodoinjava: DEBUG
org.hibernate: ERROR
|
In above configuration, I upgraded log level for application classes to DEBUG (from default INFO). Now observe the logs:
2017
-
03
-
02
23
:
57
:
14.966
DEBUG
4092
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : debug log statement printed
2017
-
03
-
02
23
:
57
:
14.967
INFO
4092
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : info log statement printed
2017
-
03
-
02
23
:
57
:
14.967
WARN
4092
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : warn log statement printed
2017
-
03
-
02
23
:
57
:
14.967
ERROR
4092
--- [nio-
8080
-exec-
1
] c.h.app.controller.IndexController : error log statement printed
|
Set logging pattern
To change the loging patterns, use logging.pattern.console and logging.pattern.file keys.
logging:
pattern:
console: %d{yyyy-MM-dd HH:mm:ss} - %msg%n
file: %d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{
36
} - %msg%n
|
After changing console logging pattern in application, log statements are printed as below:
2017
-
03
-
03
12
:
59
:
13
- This is a debug message
2017
-
03
-
03
12
:
59
:
13
- This is an info message
2017
-
03
-
03
12
:
59
:
13
- This is a warn message
2017
-
03
-
03
12
:
59
:
13
- This is an error message
|
Set logging output to file
To print the logs in file, use logging.file or logging.path key.
logging:
file: /logs/application-debug.log
|
Verify the logs in file.
2017
-
03
-
03
13
:
02
:
50.608
DEBUG
10424
--- [http-nio-
8080
-exec-
1
] c.h.app.controller.IndexController : This is a debug message
2017
-
03
-
03
13
:
02
:
50.608
INFO
10424
--- [http-nio-
8080
-exec-
1
] c.h.app.controller.IndexController : This is an info message
2017
-
03
-
03
13
:
02
:
50.608
WARN
10424
--- [http-nio-
8080
-exec-
1
] c.h.app.controller.IndexController : This is a warn message
2017
-
03
-
03
13
:
02
:
50.609
ERROR
10424
--- [http-nio-
8080
-exec-
1
] c.h.app.controller.IndexController : This is an error message
|
Using active profiles to load environment specific logging configuration
It is desirable to have multiple configurations for any application – where each configuration is specific to a particular runtime environment. In spring boot, you can achieve this by creating multiple application-{profile}.yml files in same location as application.yml file.
Profile specific keys always override the non-profile specific ones. If several profiles are specified, a last wins strategy applies.
If I have two environments for my application i.e. prod and dev. Then I will create two profile specific yml files.
application-dev.yml
logging:
file: logs/application-debug.log
pattern:
console:
"%d %-5level %logger : %msg%n"
file:
"%d %-5level [%thread] %logger : %msg%n"
level:
org.springframework.web: ERROR
com.howtodoinjava: DEBUG
org.hibernate: ERROR
|
application-prod.yml
logging:
file: logs/application-debug.log
pattern:
console:
"%d %-5level %logger : %msg%n"
file:
"%d %-5level [%thread] %logger : %msg%n"
level:
org.springframework.web: ERROR
com.howtodoinjava: INFO
org.hibernate: ERROR
|
To supply profile information to application, key spring.profiles.active is passed to runtime.
$ java -jar -Dspring.profiles.active=prod spring-boot-demo.jar
|
Color-coded logging output
If your terminal supports ANSI, color output will be used to aid readability. You can set spring.output.ansi.enabled value to either ALWAYS, NEVER or DETECT.
spring:
output:
ansi:
enabled: DETECT
|
Color coding is configured using the %clr conversion word. In its simplest form the converter will color the output according to the log level.
FATAL and ERROR – Red
WARN – Yellow
INFO, DEBUG and TRACE – Green
Drop me your questions in comments section.
Happy Learning !!
References:
Spring Boot – How to logging
Spring boot features – Logging
