Spring Gateway依赖引发clientRegistrationRepository不能为空异常排查

我用WebFlux结合Okta实现OAuth2.0认证，此前相同配置的项目能正常运行，但重新创建或部署时出现clientRegistrationRepository不能为空的错误。逐个移除依赖排查后，确认是spring-cloud-starter-gateway-mvc依赖导致的问题。

相关配置如下：

OAuth2LoginConfig.java #

@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginConfig {
    @Bean
    public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
        http
            .authorizeExchange(authorize -> authorize
                .anyExchange().authenticated()
            )
            .oauth2Login(Customizer.withDefaults());

        return http.build();
    }
}

application.yml #

server:
  port: 9098

spring:
  main:
    allow-bean-definition-overriding: true
 
  application:
    name: dummy-okta
    
eureka:
  instance:
    prefer-ip-address: true
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://localhost:8761/eureka

okta:
  oauth2:
    issuer: https://dev-27305929.okta.com/oauth2/default
    audience: api://default
    client-id: 0oahgmcygbKzqfnwk5d7
    client-secret: CJTkPspyDVwiNLTvtPWySF-R8P30yi2x8aWuy-272SXIwYlUcLzUZ93LSJjuj-Ev
    scopes: openid, profile, email, offline_access

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>3.2.6</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>okta-dummy</groupId>
    <artifactId>com.api.gateway</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>okta-dummy</name>
    <description>okta dummy test project</description>
    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>
    <dependencies>
    
    <!-- okta security and spring security dependancy -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>com.okta.spring</groupId>
            <artifactId>okta-spring-boot-starter</artifactId>
            <version>3.0.6</version>
        </dependency>
        
        <!-- cloud gateway and webflux dependancy -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway-mvc</artifactId>
        </dependency>
        
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-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>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

问题根源 #

spring-cloud-starter-gateway-mvc是基于Servlet栈的网关实现，而你使用的WebFlux属于Reactive响应式栈，两者引入的Spring Security组件存在冲突：

• Okta的starter会根据当前环境自动创建对应的ClientRegistrationRepositoryBean：Reactive环境下应该创建ReactiveClientRegistrationRepository，Servlet环境下创建ClientRegistrationRepository。
• 引入Gateway MVC依赖后，类路径中混入了Servlet栈的Security类，导致Spring容器优先加载Servlet版本的Bean，而你的SecurityWebFilterChain（Reactive栈）需要的是ReactiveClientRegistrationRepository，最终因找不到匹配的Bean报错“clientRegistrationRepository不能为空”。

解决步骤 #

1. 替换网关依赖：把spring-cloud-starter-gateway-mvc换成spring-cloud-starter-gateway——这是专门为WebFlux设计的Reactive网关依赖，和你的技术栈完全匹配：

   <!-- 移除冲突依赖 -->
   <!-- <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-gateway-mvc</artifactId>
   </dependency> -->
   
   <!-- 添加正确的Reactive网关依赖 -->
   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-gateway</artifactId>
   </dependency>
   

2. 清理冲突依赖：检查pom.xml，确保没有同时引入Servlet栈的Web依赖（比如spring-boot-starter-web），避免类路径冲突。
3. 重新构建验证：执行mvn clean install清理并构建项目，启动后Okta的starter会自动创建ReactiveClientRegistrationRepositoryBean，配合@EnableWebFluxSecurity就能正常完成OAuth2认证流程。

内容的提问来源于stack exchange，提问作者Rani