日志体系：SLF4J 门面与 Logback 配置实战

logging:  level:    root: INFO                 # 兜底：所有未单独配置的走 INFO    com.example.order: DEBUG   # 只有订单包开 DEBUG

// 反例：拼接在 log 之前就执行了，级别再低也白拼logger.debug("查询用户 id=" + userId + ", 名称=" + name + ", 耗时=" + cost + "ms");// 正例：只有级别放行时才真正做字符串替换logger.debug("查询用户 id={}, 名称={}, 耗时={}ms", userId, name, cost);

try {    orderService.create(order);} catch (Exception e) {    // 异常对象放最后，SLF4J 自动识别并打印完整堆栈    log.error("创建订单失败 orderId={}, userId={}", order.getId(), order.getUserId(), e);}

logging:  level:                                   # ① 改级别：不改代码，按包精细控制    root: INFO    com.example: DEBUG    org.springframework.jdbc.core: DEBUG   # 想看 SQL 参数时打开    com.zaxxer.hikari: INFO                # 连接池日志别刷屏  file:    name: ./logs/bee.log                   # ② 同时输出到文件（控制台依然保留）  pattern:    console: "%d{HH:mm:ss.SSS} %-5level [%X{traceId}] %logger{36} - %msg%n"    file: "%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%X{traceId}] %logger{36} - %msg%n"

# 只把订单包临时调到 DEBUG，其他包不受影响curl -X POST http://localhost:8080/actuator/loggers/com.example.order \  -H 'Content-Type: application/json' \  -d '{"configuredLevel":"DEBUG"}'# 查当前生效级别curl http://localhost:8080/actuator/loggers/com.example.order

<?xml version="1.0" encoding="UTF-8"?><configuration scan="true" scanPeriod="60 seconds">    <!-- 1. 变量：日志目录与文件前缀，改一处即可全局生效 -->    <property name="LOG_HOME" value="./logs"/>    <property name="APP_NAME" value="bee"/>    <!-- 2. 控制台：开发时看的，带颜色高亮 -->    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">        <encoder>            <pattern>%d{HH:mm:ss.SSS} %highlight(%-5level) [%thread] %cyan(%logger{36}) - %msg%n</pattern>        </encoder>    </appender>    <!-- 3. 文件：按天 + 按大小双维度滚动，历史 gzip 压缩 -->    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">        <file>${LOG_HOME}/${APP_NAME}.log</file>        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">            <fileNamePattern>${LOG_HOME}/${APP_NAME}.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>            <maxFileSize>100MB</maxFileSize>            <maxHistory>30</maxHistory>            <totalSizeCap>5GB</totalSizeCap>        </rollingPolicy>        <encoder>            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%thread] [%X{traceId}] %logger{36} - %msg%n</pattern>        </encoder>    </appender>    <!-- 4. 异步包装：业务线程只写队列，落盘交给后台线程 -->    <appender name="ASYNC_FILE" class="ch.qos.logback.classic.AsyncAppender">        <queueSize>1024</queueSize>        <discardingThreshold>0</discardingThreshold>        <neverBlock>true</neverBlock>        <appender-ref ref="FILE"/>    </appender>    <!-- 5. 按级别分流：ERROR 单独一封，方便告警系统直接 tail -->    <appender name="ERROR_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">        <file>${LOG_HOME}/${APP_NAME}-error.log</file>        <filter class="ch.qos.logback.classic.filter.LevelFilter">            <level>ERROR</level>            <onMatch>ACCEPT</onMatch>            <onMismatch>DENY</onMismatch>        </filter>        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">            <fileNamePattern>${LOG_HOME}/${APP_NAME}-error.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>            <maxFileSize>50MB</maxFileSize>            <maxHistory>60</maxHistory>        </rollingPolicy>        <encoder><pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%X{traceId}] %msg%n</pattern></encoder>    </appender>    <!-- 6. 包级别：自己的业务包放开，第三方框架压到 WARN -->    <logger name="com.example" level="DEBUG"/>    <logger name="org.apache.ibatis" level="WARN"/>    <logger name="com.zaxxer.hikari" level="INFO"/>    <root level="INFO">        <appender-ref ref="CONSOLE"/>        <appender-ref ref="ASYNC_FILE"/>        <appender-ref ref="ERROR_FILE"/>    </root></configuration>

<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">    <fileNamePattern>./logs/bee.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>    <maxFileSize>100MB</maxFileSize>   <!-- 单文件超过 100MB 就滚，%i 递增 -->    <maxHistory>30</maxHistory>        <!-- 只保留最近 30 天 -->    <totalSizeCap>5GB</totalSizeCap>   <!-- 所有归档加起来不超过 5GB --></rollingPolicy>

package com.example.web.filter;import jakarta.servlet.FilterChain;import jakarta.servlet.ServletException;import jakarta.servlet.http.HttpServletRequest;import jakarta.servlet.http.HttpServletResponse;import org.slf4j.MDC;import org.springframework.core.Ordered;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;import org.springframework.web.filter.OncePerRequestFilter;import java.io.IOException;import java.util.UUID;@Component@Order(Ordered.HIGHEST_PRECEDENCE)public class TraceIdFilter extends OncePerRequestFilter {    public static final String TRACE_ID = "traceId";    @Override    protected void doFilterInternal(HttpServletRequest request,                                    HttpServletResponse response,                                    FilterChain chain) throws ServletException, IOException {        // 上游网关已透传就沿用，保证全链路同一个 ID        String traceId = request.getHeader("X-Trace-Id");        if (traceId == null || traceId.isBlank()) {            traceId = UUID.randomUUID().toString().replace("-", "").substring(0, 16);        }        MDC.put(TRACE_ID, traceId);        response.setHeader("X-Trace-Id", traceId);        try {            chain.doFilter(request, response);        } finally {            MDC.remove(TRACE_ID);   // 必须清理，否则线程复用会串味        }    }}

@EnableAsync@Configurationpublic class AsyncConfig implements AsyncConfigurer {    @Override    public Executor getAsyncExecutor() {        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();        executor.setCorePoolSize(8);        executor.setMaxPoolSize(16);        executor.setQueueCapacity(200);        executor.setThreadNamePrefix("async-");        executor.setTaskDecorator(new MdcTaskDecorator());  // 关键：传递 MDC        executor.initialize();        return executor;    }}class MdcTaskDecorator implements TaskDecorator {    @Override    public Runnable decorate(Runnable runnable) {        Map<String, String> context = MDC.getCopyOfContextMap();  // 提交线程快照        return () -> {            try {                if (context != null) MDC.setContextMap(context);  // 在子线程还原                runnable.run();            } finally {                MDC.clear();   // 归还线程前清空，避免污染下一个任务            }        };    }}

@Componentpublic class TraceFeignInterceptor implements RequestInterceptor {    @Override    public void apply(RequestTemplate template) {        String traceId = MDC.get("traceId");        if (traceId != null) {            template.header("traceparent", "00-" + traceId + "-" + spanId() + "-01");        }    }}

{"@timestamp":"2026-10-07T10:12:33.482Z","level":"ERROR","logger_name":"com.example.order.OrderService","thread_name":"http-nio-8080-exec-3","traceId":"9f2c1a7b3e5d8401","message":"创建订单失败 orderId=10023","stack_trace":"java.lang.RuntimeException: 库存不足..."}

int failed = 0;for (Order order : orders) {    try { importService.handle(order); }    catch (Exception e) { failed++; log.warn("单条导入失败 orderId={}", order.getId(), e); }}log.info("批量导入完成 total={}, failed={}", orders.size(), failed);