Spring云网关；在类路径中发现 Spring MVC，与 Spring Cloud Gateway 问题不兼容

Question

运行 API-GATEWAY 时出现以下错误，我尝试了很多方法但无法解决此问题。

描述：

在类路径中发现 Spring MVC，与 Spring Cloud Gateway 不兼容。

行动：

请设置 spring.main.web-application-type=reactive 或删除 spring-boot-starter-web 依赖。

主班

package com.sample.apigateway;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class ApiGatewayApplication {

    public static void main(String[] args) {
        SpringApplication.run(ApiGatewayApplication.class, args);
    }

}

应用程序.yml

spring:
  application:
    name: GATEWAY-SERVICE

  cloud:
    gateway:
      routes:
        - id: USER-SERVICE
          uri: lb://USER-SERVICE
          predicates:
            - Path=/users/**
        - id: DEPARTMENT-SERVICE
          uri: lb://DEPARTMENT-SERVICE
          predicates:
            - Path=/departments/**

eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:8761/eureka/

  instance:
    hostname: localhost

server:
  port: 9191

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.5.3</version>
    <relativePath/>
    <!-- lookup parent from repository -->
  </parent>
  <groupId>com.sample.apigateway</groupId>
  <artifactId>apigateway</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>apigateway</name>
  <description>Demo project for Spring Boot</description>
  <properties>
    <java.version>11</java.version>
    <spring-cloud.version>2020.0.3</spring-cloud.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
    <dependency>
      <groupId>io.springfox</groupId>
      <artifactId>springfox-boot-starter</artifactId>
      <version>3.0.0</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-gateway</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>

</project>

完整错误消息

2021-07-30 23:12:02.420  WARN 19032 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration$SpringMvcFoundOnClasspathConfiguration': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration$SpringMvcFoundOnClasspathConfiguration]: Constructor threw exception; nested exception is org.springframework.cloud.gateway.support.MvcFoundOnClasspathException
2021-07-30 23:12:02.423  INFO 19032 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-07-30 23:12:02.441  INFO 19032 --- [           main] ConditionEvaluationReportLoggingListener :

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-07-30 23:12:02.454 ERROR 19032 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   :

***************************
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.


Process finished with exit code 1

Answer 1

我面临着类似的问题。正如错误部分中所建议的，对 application.properties 文件进行以下更改对我来说效果很好。

spring.main.web-application-type=reactive

Answer 2

请注意，Spring Cloud Gateway与 Spring MVC 不兼容 ( spring-boot-starter-web)。“如何将 Spring Cloud Gateway 包含在官方参考文档中”部分对此进行了概述：

Spring Cloud Gateway 基于 Spring Boot 2.x、Spring WebFlux 和 Project Reactor 构建。因此，当您使用 Spring Cloud Gateway 时，您所知道的许多熟悉的同步库（例如 Spring Data 和 Spring Security）和模式可能不适用。

此外，还指出：

Spring Cloud Gateway 需要 Spring Boot 和 Spring Webflux 提供的 Netty 运行时。它不适用于传统的 Servlet 容器或构建为 WAR 时。

正如错误消息已经建议的那样，您需要删除对spring-boot-starter-web. 您可以使用以下命令列出所有直接和传递依赖项：

mvn dependency:tree

这将揭示spring-cloud-starter-netflix-eureka-server取决于spring-boot-starter-web. 从您的 中删除以下行后pom.xml，您的应用程序应该启动：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>