Logging systems consist of logging facades and implementations (similar to JDBC and data base drivers relationship). The facade provides a unified interface while allowing switching between different logging implementations.

Spring Boot Logging Architecture

Spring Boot uses SLF4J as the logging facade and Logback as the default implementation, while also supporting other frameworks like Java Util Logging and Log4J2.

The spring-boot-starter-logging dependency automatically configures these frameworks. During startup, Spring Boot creates a SpringApplication instence and initializes the logging system through the LoggingApplicationListener which responds to various application events.

Configuration Opsions

Logging can be configured via:

• Log patterns: logging.pattern
• Log levels: logging.level
• File output: logging.file
• Log rotation: logging.logback.rollingpolicy

Implementation Examples

Traditional Logger Usage

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@RestController
public class DemoController {
    private static final Logger log = LoggerFactory.getLogger(DemoController.class);
    
    @GetMapping("/demo")
    public String demoEndpoint() {
        log.debug("Processing demo request");
        return "Demo response";
    }
}

Lombok Simplified Logger

import lombok.extern.slf4j.Slf4j;

@Slf4j
@RestController
public class DemoController {
    @GetMapping("/demo")
    public String demoEndpoint() {
        log.info("Handling demo request");
        return "Demo response";
    }
}