解决Gateway报错Spring MVC found on classpath, which is incompatible with Spring Cloud Gateway

报错信息如下

        

202X-XX-XX XX:XX:XX.XXX [WARN] [main] org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:592) 
 Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration$SpringMvcFoundOnClasspathConfiguration': Failed to instantiate [org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration$SpringMvcFoundOnClasspathConfiguration]: Constructor threw exception
202X-XX-XX XX:XX:XX.XXX [INFO] [main] org.apache.juli.logging.DirectJDKLog.log(DirectJDKLog.java:173) 
 Stopping service [Tomcat]
202X-XX-XX XX:XX:XX.XXX [ERROR] [main] org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter.report(LoggingFailureAnalysisReporter.java:40) 
 

***************************
APPLICATION FAILED TO START
***************************

Description:

Spring MVC found on classpath, which is incompatible with Spring Cloud Gateway.

Action:

Please set spring.main.web-application-type=reactive or remove spring-boot-starter-web dependency.
 

解决办法

这是因为 Spring Cloud Gateway 的项目中不能使用 Spring MVC 的依赖，一般是你通过依赖其它模块而间接引用了该 Spring MVC 的依赖。 

也就是说，在 Spring Cloud Gateway 的项目中不能使用如下依赖。

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

  如果不小心引用了，则需要排除 Spring MVC 依赖。

<dependency>
    <groupId>某个引用了 Spring MVC 依赖的模块的组 ID</groupId>
    <artifactId>该模块的工件 ID</artifactId>
    <version>该工件的版本号</version>
    <exclusions>
        <!-- Spring Cloud Gateway 项目中不能使用 spring-boot-starter-web 依赖-->
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </exclusion>
    </exclusions>
</dependency>