【原創】大叔經驗分享（67）spring boot啟動報錯

spring boot 啟動報錯：

Caused by: java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext but Logback is on the classpath. Either remove Logback or the competing implementation (class org.slf4j.impl.Log4jLoggerFactory loaded from file:/usr/local/tomcat/webapps/app/WEB-INF/lib/slf4j-log4j12-1.7.25.jar). If you are using WebLogic you will need to add 'org.slf4j' to prefer-application-packages in WEB-INF/weblogic.xml: org.slf4j.impl.Log4jLoggerFactory
        at org.springframework.util.Assert.instanceCheckFailed(Assert.java:655)
        at org.springframework.util.Assert.isInstanceOf(Assert.java:555)
        at org.springframework.boot.logging.logback.LogbackLoggingSystem.getLoggerContext(LogbackLoggingSystem.java:286)
        at org.springframework.boot.logging.logback.LogbackLoggingSystem.beforeInitialize(LogbackLoggingSystem.java:102)
        at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationStartingEvent(LoggingApplicationListener.java:220)
        at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:199)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
        at org.springframework.boot.context.event.EventPublishingRunListener.starting(EventPublishingRunListener.java:69)
        at org.springframework.boot.SpringApplicationRunListeners.starting(SpringApplicationRunListeners.java:48)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:302)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.run(SpringBootServletInitializer.java:157)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.createRootApplicationContext(SpringBootServletInitializer.java:137)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.onStartup(SpringBootServletInitializer.java:91)
        at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:171)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5139)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
        ... 26 more

出現這個問題通常的原因工程中使用了多個開源jar，每個開源jar都有自己的日志實現方式，比如slf+log4j,slf+logback等，其中slf是一個抽象接口，有很多種實現，但是工程中只能有一種，解決方法在異常中已經提示出來：

Either remove Logback or the competing implementation (class org.slf4j.impl.Log4jLoggerFactory loaded from file:/usr/local/tomcat/webapps/app/WEB-INF/lib/slf4j-log4j12-1.7.25.jar). 

需要在logback和slf-log4j之間去掉一個，其中spring boot用的是logback，可以去掉slf-log4j；

通過

mvn dependency:tree

可以看到那些jar中依賴了slf-log4j，然后修改pom，將其排除掉

        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.6.5</version>
            <exclusions>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-log4j12</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

然后打包即可；