Spring Boot中log4j的配置

上篇文章Spring Boot日志管理，我简单讲述了Spring Boot中使用默认日志Logback进行日志管理的配置。在上篇文章中有讲到，LogBack是Log4j的改良版本，比Log4j拥有更多的特性，同时也带来很大性能提升。但是log4j作为一款常用的日志库，在实际开发中还是很常用的，本片文章，我将简单介绍一下Spring Boot中如何使用Log4J进行日志管理。

创建Spring Boot工程时，必然会引入了spring-boot-starter，其中包含了spring-boot-starter-logging，该依赖内容就是Spring Boot默认的日志框架Logback，所以我们在引入log4j之前，首先要先排除该包的依赖，再引入log4j的依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

在src/main/resuorces文件夹添加log4j配置文件log4j2.xml：

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" monitorInterval="30">
    <Properties>
        <Property name="LOG_PATTERN">
            %d{yyyy-MM-dd HH:mm:ss.SSS} %5p ${hostName} --- [%15.15t] %-40.40c{1.} : %m%n%ex
        </Property>
    </Properties>
    <Appenders>
        <Console name="ConsoleAppender" target="SYSTEM_OUT" follow="true">
            <PatternLayout pattern="${LOG_PATTERN}"/>
        </Console>
    </Appenders>
    <Loggers>
        <Logger name="com.example.log4j2demo" level="debug" additivity="false">
            <AppenderRef ref="ConsoleAppender"/>
        </Logger>

        <Root level="info">
            <AppenderRef ref="ConsoleAppender"/>
        </Root>
    </Loggers>
</Configuration>

log4J也可以和SLF4J配合使用，实现运行时绑定log4J实例，使用方法与上一篇文章logback一致。

@RestController
@RequestMapping(value = "/health")
public class HealthCheckController {
    private final Logger logger = LoggerFactory.getLogger(Object.class);

    @RequestMapping(value = "/check", method = RequestMethod.GET)
    public String check(){
        logger.trace("health check controller trace……");
        logger.debug("health check controller debug……");
        logger.info("health check controller info……");
        logger.warn("health check controller warn……");
        logger.error("health check controller error……");
        return "ok";
    }
}

• Log4j文件输出配置

在Logback中可以通过配置RollingFile子节点达到文件输出的目的，配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" monitorInterval="30">
    <Properties>
        <Property name="LOG_PATTERN">
            %d{yyyy-MM-dd HH:mm:ss.SSS} %5p ${hostName} --- [%15.15t] %-40.40c{1.} : %m%n%ex
        </Property>
    </Properties>
    <Appenders>
        <Console name="ConsoleAppender" target="SYSTEM_OUT" follow="true">
            <PatternLayout pattern="${LOG_PATTERN}"/>
        </Console>

        <RollingFile name="FileAppender" fileName="d:/log/log4j2-demo.log"
                     filePattern="d:/log/log4j2-demo-%d{yyyy-MM-dd}-%i.log">
            <PatternLayout>
                <Pattern>${LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <SizeBasedTriggeringPolicy size="10MB" />
            </Policies>
            <DefaultRolloverStrategy max="10"/>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Logger name="com.zhuoli.service.springboot.log4j" level="debug" additivity="false">
            <AppenderRef ref="ConsoleAppender" />
        </Logger>

        <Root level="info">
            <AppenderRef ref="ConsoleAppender" />
            <AppenderRef ref="FileAppender" />
        </Root>
    </Loggers>
</Configuration>

• Log4j异步日志

log4j启动异步需要lmax支持，需要引入jar包：

<!-- Needed for Async Logging with Log4j 2 -->
<dependency>
    <groupId>com.lmax</groupId>
    <artifactId>disruptor</artifactId>
    <version>3.3.6</version>
</dependency>

修改日志输出为异步：

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" monitorInterval="30">
    <Properties>
        <Property name="LOG_PATTERN">
            %d{yyyy-MM-dd HH:mm:ss.SSS} %5p ${hostName} --- [%15.15t] %-40.40c{1.} : %m%n%ex
        </Property>
    </Properties>
    <Appenders>
        <Console name="ConsoleAppender" target="SYSTEM_OUT" follow="true">
            <PatternLayout pattern="${LOG_PATTERN}"/>
        </Console>

        <RollingFile name="FileAppender" fileName="d:/log/log4j2-demo.log"
                     filePattern="d:/log/log4j2-demo-%d{yyyy-MM-dd}-%i.log">
            <PatternLayout>
                <Pattern>${LOG_PATTERN}</Pattern>
            </PatternLayout>
            <Policies>
                <SizeBasedTriggeringPolicy size="10MB" />
            </Policies>
            <DefaultRolloverStrategy max="10"/>
        </RollingFile>

        <!--file异步输出-->
        <Async name="AsyncFile" buffersize="32768" blocking="false">
            <AppenderRef ref="FileAppender"/>
        </Async>

        <!--console异步输出-->
        <Async name="AsyncConsole" buffersize="32768" blocking="false">
            <AppenderRef ref="ConsoleAppender"/>
        </Async>
    </Appenders>
    <Loggers>
        <Logger name="org.apache.catalina.startup.DigesterFactory" level="error"/>
        <Logger name="org.apache.catalina.util.LifecycleBase" level="error"/>
        <Logger name="org.apache.coyote.http11.Http11NioProtocol" level="warn"/>
        <logger name="org.apache.sshd.common.util.SecurityUtils" level="warn"/>
        <Logger name="org.apache.tomcat.util.net.NioSelectorPool" level="warn"/>
        <Logger name="org.crsh.plugin" level="warn"/>
        <logger name="org.crsh.ssh" level="warn"/>
        <Logger name="org.eclipse.jetty.util.component.AbstractLifeCycle" level="error"/>
        <Logger name="org.hibernate.validator.internal.util.Version" level="warn"/>
        <logger name="org.springframework.boot.actuate.autoconfigure.CrshAutoConfiguration" level="warn"/>
        <logger name="org.springframework.boot.actuate.endpoint.jmx" level="warn"/>
        <logger name="org.thymeleaf" level="warn"/>
        <logger name="org.springframework.context.support" level="warn"/>
        <logger name="org.springframework.jmx.export.annotation" level="warn"/>
        <logger name="com.zaxxer.hikari" level="warn"/>
        <logger name="org.springframework.context.annotation.AnnotationConfigApplicationContext" level="warn"/>
        <logger name="org.springframework.web.servlet.mvc.method.annotation" level="warn"/>
        <logger name="metrics_influxdb.measurements" level="off"/>

        <Root level="info">
            <AppenderRef ref="AsyncConsole" />
            <AppenderRef ref="AsyncFile" />
        </Root>
    </Loggers>
</Configuration>

上述配置实现了日志异步输出，及区别包进行不同级别的log输出，在日常开发中基本是可用的。通过本片文章可以看出，其实log4j配置和logback配置是相通的，建议想了解日志配置的同学花时间去看一下上篇Spring Boot日志管理的文章。另外，在生产上，通过kafaka异步日志输出也是非常常见的，想了解的同学可以看一下这一篇文章Kafka+Log4j实现日志集中管理

示例代码：码云 – 卓立 – Spring Boot + log4j日志配置