Spring Boot 中 Log4j2 日志配置指南

2. 添加 Log4j2 依赖

然后添加 Log4j2 相关依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>
<!-- 高性能异步日志库 -->
<dependency>
    <groupId>com.lmax</groupId>
    <artifactId>disruptor</artifactId>
    <version>3.4.4</version>
</dependency>

三、application.yml 配置

在 application.yml 文件中指定日志配置文件：

logging:
  config: classpath:log4j2.xml

这样配置可以让 Spring Boot 加载自定义的 Log4j2 配置文件。

四、log4j2.xml 完整配置详解

1. Properties 属性定义

<Properties>
    <property name="LOG_HOME" value="./logs"/>
    <property name="APP_CODE" value="file_log"/>
    <property name="LOG_LEVEL_PATTERN" value="%-5p"/>
    <property name="INSTANCE_INFO_PATTERN" value="${hostName} | ${sys:user.name}"/>
    <property name="CODE_INFO_PATTERN" value="%pid:%F:%L"/>
    <property name="LOG_DATEFORMAT_PATTERN" value="yyyy-MM-dd HH:mm:ss.SSS"/>
    <property name="APP_LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} | ${LOG_LEVEL_PATTERN} | %X{TRACE_ID} | %t | ${CODE_INFO_PATTERN} | [%X{seq}] - %m%n"/>
    <property name="LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} | %X{TRACE_ID} | ${LOG_LEVEL_PATTERN} | ${INSTANCE_INFO_PATTERN} | FEIA | FLEP-INAPP | %t | ${CODE_INFO_PATTERN} | %m%n"/>
    <property name="ALERT_LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} $${ctx:traceId:-} | ${INSTANCE_INFO_PATTERN} | [%X{seq}] - %m%n"/>
</Properties>

这里定义了日志系统的各种属性，包括日志存储路径、日志级别格式、实例信息格式等。

2. Appenders 输出配置

控制台输出配置

<Console name="Console" target="SYSTEM_OUT" follow="true">
    <PatternLayout pattern="%d{${LOG_DATEFORMAT_PATTERN}} | ${LOG_LEVEL_PATTERN} | %t | %c:%L | [%X{seq}] - %m%n"/>
</Console>

文件滚动策略配置

Log4j2 支持多种滚动策略，以下是一些常用配置：

事件日志配置：

<RollingFile name="EventLogFile" fileName="${LOG_HOME}/event.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/event.log.%i">
    <PatternLayout>
        <Pattern>${LOG_PATTERN}</Pattern>
    </PatternLayout>
    <Policies>
        <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
        <SizeBasedTriggeringPolicy size="50MB"/>
    </Policies>
    <DefaultRolloverStrategy>
        <Delete basePath="${LOG_HOME}" maxDepth="2">
            <IfFileName glob="*/event.log.*"/>
            <IfLastModified age="30d"/>
        </Delete>
    </DefaultRolloverStrategy>
</RollingFile>

应用日志配置：

<RollingFile name="AppLogFile" fileName="${LOG_HOME}/app.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/app.log.%i">
    <PatternLayout>
        <Pattern>${APP_LOG_PATTERN}</Pattern>
    </PatternLayout>
    <Policies>
        <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
        <SizeBasedTriggeringPolicy size="50MB"/>
    </Policies>
    <DefaultRolloverStrategy>
        <Delete basePath="${LOG_HOME}" maxDepth="2">
            <IfFileName glob="*/app.log.*"/>
            <IfLastModified age="30d"/>
        </Delete>
    </DefaultRolloverStrategy>
</RollingFile>

告警日志配置：

<RollingFile name="AlertLogFile" fileName="${LOG_HOME}/alert.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/alert.log.%i">
    <thresholdFilter level="warn" onMatch="ACCEPT" onMismatch="DENY"/>
    <PatternLayout>
        <Pattern>${ALERT_LOG_PATTERN}</Pattern>
    </PatternLayout>
    <Policies>
        <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
        <SizeBasedTriggeringPolicy size="50MB"/>
    </Policies>
    <DefaultRolloverStrategy>
        <Delete basePath="${LOG_HOME}" maxDepth="2">
            <IfFileName glob="*/alert.log.*"/>
            <IfLastModified age="30d"/>
        </Delete>
    </DefaultRolloverStrategy>
</RollingFile>

错误日志配置：

<RollingFile name="ErrorLogFile" fileName="${LOG_HOME}/error.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/error.log.%i">
    <thresholdFilter level="error" onMatch="ACCEPT" onMismatch="DENY"/>
    <PatternLayout>
        <Pattern>${APP_LOG_PATTERN}</Pattern>
    </PatternLayout>
    <Policies>
        <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
        <SizeBasedTriggeringPolicy size="50MB"/>
    </Policies>
    <DefaultRolloverStrategy>
        <Delete basePath="${LOG_HOME}" maxDepth="2">
            <IfFileName glob="*/error.log.*"/>
            <IfLastModified age="30d"/>
        </Delete>
    </DefaultRolloverStrategy>
</RollingFile>

3. Loggers 日志记录器配置

Root Logger 配置

<Root level="INFO">
    <AppenderRef ref="Console"/>
    <AppenderRef ref="AppLogFile"/>
    <AppenderRef ref="AlertLogFile"/>
    <AppenderRef ref="ErrorLogFile"/>
</Root>

异步日志记录器配置

<AsyncLogger name="event" level="ALL" additivity="false">
    <AppenderRef ref="EventLogFile"/>
</AsyncLogger>

特定包的日志级别配置

<logger name="com.apache.ibatis" level="TRACE"/>
<logger name="java.sql.Connection" level="DEBUG"/>
<logger name="java.sql.Statement" level="DEBUG"/>
<logger name="java.sql.PreparedStatement" level="DEBUG"/>
<logger name="com.cisdi.colmet.core.mapper" level="DEBUG"/>

性能优化建议

1. 合理设置日志级别，避免输出过多调试信息
2. 使用异步日志记录提高性能
3. 合理设置日志文件大小和保留策略
4. 定期监控日志磁盘使用情况

五、完整配置示例

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" monitorInterval="600">
    <Properties>
        <property name="LOG_HOME" value="./logs"/>
        <property name="APP_CODE" value="file_log"/>
        <property name="LOG_LEVEL_PATTERN" value="%-5p"/>
        <property name="INSTANCE_INFO_PATTERN" value="${hostName} | ${sys:user.name}"/>
        <property name="CODE_INFO_PATTERN" value="%pid:%F:%L"/>
        <property name="LOG_DATEFORMAT_PATTERN" value="yyyy-MM-dd HH:mm:ss.SSS"/>
        <property name="APP_LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} | ${LOG_LEVEL_PATTERN} | %X{TRACE_ID} | %t | ${CODE_INFO_PATTERN} | [%X{seq}] - %m%n"/>
        <property name="LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} | %X{TRACE_ID} | ${LOG_LEVEL_PATTERN} | ${INSTANCE_INFO_PATTERN} | FEIA | FLEP-INAPP | %t | ${CODE_INFO_PATTERN} | %m%n"/>
        <property name="ALERT_LOG_PATTERN" value="%d{${LOG_DATEFORMAT_PATTERN}} $${ctx:traceId:-} | ${INSTANCE_INFO_PATTERN} | [%X{seq}] - %m%n"/>
    </Properties>
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT" follow="true">
            <PatternLayout pattern="%d{${LOG_DATEFORMAT_PATTERN}} | ${LOG_LEVEL_PATTERN} | %t | %c:%L | [%X{seq}] - %m%n"/>
        </Console>
        <RollingFile name="EventLogFile" fileName="${LOG_HOME}/event.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/event.log.%i">
            <PatternLayout>
                <Pattern>${LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
                <SizeBasedTriggeringPolicy size="50MB"/>
            </Policies>
            <DefaultRolloverStrategy>
                <Delete basePath="${LOG_HOME}" maxDepth="2">
                    <IfFileName glob="*/event.log.*"/>
                    <IfLastModified age="30d"/>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingFile>
        <RollingFile name="AppLogFile" fileName="${LOG_HOME}/app.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/app.log.%i">
            <PatternLayout>
                <Pattern>${APP_LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
                <SizeBasedTriggeringPolicy size="50MB"/>
            </Policies>
            <DefaultRolloverStrategy>
                <Delete basePath="${LOG_HOME}" maxDepth="2">
                    <IfFileName glob="*/app.log.*"/>
                    <IfLastModified age="30d"/>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingFile>
        <RollingFile name="AlertLogFile" fileName="${LOG_HOME}/alert.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/alert.log.%i">
            <thresholdFilter level="warn" onMatch="ACCEPT" onMismatch="DENY"/>
            <PatternLayout>
                <Pattern>${ALERT_LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
                <SizeBasedTriggeringPolicy size="50MB"/>
            </Policies>
            <DefaultRolloverStrategy>
                <Delete basePath="${LOG_HOME}" maxDepth="2">
                    <IfFileName glob="*/alert.log.*"/>
                    <IfLastModified age="30d"/>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingFile>
        <RollingFile name="ErrorLogFile" fileName="${LOG_HOME}/error.log" immediateFlush="true" filePattern="${LOG_HOME}/%d{yyyyMMdd}/error.log.%i">
            <thresholdFilter level="error" onMatch="ACCEPT" onMismatch="DENY"/>
            <PatternLayout>
                <Pattern>${APP_LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
                <SizeBasedTriggeringPolicy size="50MB"/>
            </Policies>
            <DefaultRolloverStrategy>
                <Delete basePath="${LOG_HOME}" maxDepth="2">
                    <IfFileName glob="*/error.log.*"/>
                    <IfLastModified age="30d"/>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Root level="INFO">
            <AppenderRef ref="Console"/>
            <AppenderRef ref="AppLogFile"/>
            <AppenderRef ref="AlertLogFile"/>
            <AppenderRef ref="ErrorLogFile"/>
        </Root>
        <AsyncLogger name="event" level="ALL" additivity="false">
            <AppenderRef ref="EventLogFile"/>
        </AsyncLogger>
        <logger name="com.apache.ibatis" level="TRACE"/>
        <logger name="java.sql.Connection" level="DEBUG"/>
        <logger name="java.sql.Statement" level="DEBUG"/>
        <logger name="java.sql.PreparedStatement" level="DEBUG"/>
        <logger name="com.cisdi.colmet.core.mapper" level="DEBUG"/>
    </Loggers>
</Configuration>

六、总结

通过以上配置，我们可以构建一个功能完善、性能优异的 Log4j2 日志系统。这种配置不仅满足了日常开发和运维需求，还提供了高性能的异步日志记录能力。在实际项目中，可以根据具体需求调整日志级别、输出格式和文件策略，以达到最佳的监控和维护效果。

良好的日志配置是系统稳定运行和快速排错的重要保障，合理的日志管理策略能够显著提升系统的可维护性和可观测性。