JAVA Log 日志级别和使用配置示例

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class MyClass {
    private static final Logger logger = LoggerFactory.getLogger(MyClass.class);
}

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!-- 控制台输出 -->
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <!-- 文件输出 -->
    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>logs/app.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>logs/app.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <maxHistory>30</maxHistory>
        </rollingPolicy>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <!-- 异步日志 -->
    <appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="FILE"/>
        <queueSize>512</queueSize>
    </appender>
    <!-- 日志级别配置 -->
    <root level="INFO">
        <appender-ref ref="CONSOLE"/>
        <appender-ref ref="ASYNC"/>
    </root>
    <!-- 包级别日志 -->
    <logger name="com.example.service" level="DEBUG"/>
    <logger name="org.springframework" level="WARN"/>
</configuration>

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
        <RollingFile name="File" fileName="logs/app.log"
                     filePattern="logs/app-%d{yyyy-MM-dd}-%i.log">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
            <Policies>
                <TimeBasedTriggeringPolicy/>
                <SizeBasedTriggeringPolicy size="100 MB"/>
            </Policies>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Root level="info">
            <AppenderRef ref="Console"/>
            <AppenderRef ref="File"/>
        </Root>
    </Loggers>
</Configuration>

@Service
public class UserService {
    private static final Logger logger = LoggerFactory.getLogger(UserService.class);
    public User getUserById(Long id) {
        // 使用占位符，避免字符串拼接
        logger.debug("查询用户信息, userId: {}", id);
        try {
            User user = userRepository.findById(id);
            if (user != null) {
                logger.info("成功查询用户: {}", user.getUsername());
            } else {
                logger.warn("用户不存在, userId: {}", id);
            }
            return user;
        } catch (Exception e) {
            logger.error("查询用户失败, userId: {}", id, e);
            throw new RuntimeException("查询用户失败", e);
        }
    }
    // 使用条件判断提升性能
    public void processData(List<String> data) {
        if (logger.isDebugEnabled()) {
            logger.debug("处理数据, 数据量: {}, 内容: {}", data.size(), data);
        }
        // 复杂处理逻辑...
    }
}

public class ExceptionHandlingExample {
    // 不好的方式 - 丢失堆栈信息
    public void badExceptionLogging() {
        try {
            // 业务代码
        } catch (Exception e) {
            logger.error("操作失败: " + e.getMessage()); // 错误！
        }
    }
    // 好的方式 - 完整异常信息
    public void goodExceptionLogging() {
        try {
            // 业务代码
        } catch (BusinessException e) {
            logger.warn("业务异常, 用户ID: {}, 操作: {}", userId, operation, e);
        } catch (Exception e) {
            logger.error("系统异常, 用户ID: {}, 操作: {}", userId, operation, e);
        }
    }
}

public class PerformanceSensitiveClass {
    public void highPerformanceMethod() {
        // 使用lambda延迟计算，避免不必要的字符串构建
        logger.debug("处理请求参数: {}", () -> buildExpensiveLogMessage());
        // 或者使用条件判断
        if (logger.isDebugEnabled()) {
            logger.debug("详细数据: {}", expensiveDataToString());
        }
    }
    private String buildExpensiveLogMessage() {
        // 构建复杂的日志消息
        return "expensive message";
    }
}

logging:
  level:
    com.example: DEBUG
    org.springframework: WARN
  file:
    name: logs/app.log
  pattern:
    console: "%d{yyyy-MM-dd HH:mm:ss} - %logger{36} - %msg%n"
    file: "%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n"