1、SpringCloud与SpringBoot版本冲突

[INFO] Validation error:

[ERROR] org.apache.maven.artifact.InvalidArtifactRTException: For artifact {org.springframework.cloud:spring-cloud-starter-netflix-eureka-server:null:jar}: The version cannot be empty.
[ERROR] Maven server structure problem

[ERROR] org.apache.maven.artifact.InvalidArtifactRTException: For artifact {org.springframework.cloud:spring-cloud-starter-netflix-eureka-server:null:jar}: The version cannot be empty.

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

2、查找SpringCloud与SpringBoot版本关系

（1）查找Spring官方说明
https://start.spring.io/actuator/info

（2）解析JSON
将https://start.spring.io/actuator/info输出内容复制到
https://www.json.cn/

（3）获取到最新的SpringCloud与SpringBoot对应关系

"spring-cloud":{
            "Hoxton.SR12":"Spring Boot >=2.2.0.RELEASE and <2.4.0.M1",
            "2020.0.3":"Spring Boot >=2.4.0.M1 and <2.5.5-SNAPSHOT",
            "2020.0.4-SNAPSHOT":"Spring Boot >=2.5.5-SNAPSHOT and <2.6.0-M1",
            "2021.0.0-M1":"Spring Boot >=2.6.0.M1 and <2.6.0-SNAPSHOT",
            "2021.0.0-SNAPSHOT":"Spring Boot >=2.6.0-SNAPSHOT"
}