Logging Configuration in Spring Boot

In Spring Boot, logging is configured on two levels, and which one you use depends on how much control you need. By default Spring Boot ships with SLF4J as the API and Logback as the implementation, so you usually don't add any logging dependency at all. For the common cases, you configure everything in application.properties or application.yml. You set log levels with the logging.level prefix — logging.level.root equals INFO as a baseline, then raise your own packages to DEBUG. You can send logs to a file with logging.file.name, and you can customize the output pattern with logging.pattern.console. That handles the majority of what most apps need. When you need full control — things like rolling log files that archive daily and keep thirty days of history, multiple appenders, or JSON output for log aggregation — you add a logback configuration file. The important detail is to name it logback-spring.xml, with the dash spring suffix, rather than plain logback.xml. The spring-aware version lets Logback use Spring features like profiles, so you can say use a JSON file appender only in the prod profile, and console only in dev. Inside that XML you define appenders, where each appender is a destination — console, a rolling file, or a remote sink — and you attach them to loggers with specific levels. A common mistake is using a plain file appender with no rolling policy, because then the log file just grows until it fills the disk. So the short version is: properties for the simple, common settings, and logback-spring.xml when you need rolling files, multiple destinations, or profile-specific behavior.