JCL 级别 Logback 级别 说明
trace TRACE 最详细的调试信息
debug DEBUG 调试信息
info INFO 一般信息
warn WARN 警告信息
error ERROR 错误信息
fatal ERROR 严重错误（JCL 中与 error 通常相同）

Spring Boot 自动配置了 SLF4J + Logback，无需额外配置：

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

@RestController
public class MyController {
    private static final Logger logger = LoggerFactory.getLogger(MyController.class);
    
    @GetMapping("/example")
    public String example() {
        logger.trace("Trace message");
        logger.debug("Debug message");
        logger.info("Info message");
        logger.warn("Warn message");
        logger.error("Error message");
        return "Hello World";
    }
}

Apache Commons Logging

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

@RestController
public class MyController {
    
    // 获取日志实例
    private static final Log logger = LogFactory.getLog(MyController.class);
    
    @GetMapping("/demo")
    public String demo() {
        // 日志级别从低到高
        logger.trace("This is a TRACE level message");
        logger.debug("This is a DEBUG level message");
        logger.info("This is an INFO level message");
        logger.warn("This is a WARN level message");
        logger.error("This is an ERROR level message");
        logger.fatal("This is a FATAL level message");
        
        return "JCL demo";
    }
}