Improved the documentation in the MCP Server Boot Starter regarding Starter selection

[sunyuhan1998]

Spring AI provides three starters for MCP servers: spring-ai-starter-mcp-server, spring-ai-starter-mcp-server-webmvc, and spring-ai-starter-mcp-server-webflux, among which spring-ai-starter-mcp-server-webflux is designed for reactive projects.

However, due to Spring Boot's default behavior, if both org.springframework.web.servlet.DispatcherServlet and org.springframework.web.reactive.DispatcherHandler are present in the classpath, Spring Boot will prioritize the former:

https://github.com/spring-projects/spring-boot/blob/0daf3f5897a9bad169ad7ebad6d79e4260a24822/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/WebApplicationType.java#L60-L71

This means that if users mistakenly use spring-ai-starter-mcp-server-webflux in a project built with spring-boot-starter-web, MCP endpoints such as /sse will become non-functional.

Of course, this is not an issue with Spring AI itself. However, considering that it has already caused considerable confusion :

• Is it supported to expose MCP tools by adding spring-ai-starter-mcp-server-webflux to a legacy WebMVC app? No endpoint GET /sse error #3499
• 我用spring ai实现一个mcp server.服务起来后，一直无法访问/sse端点 #2732

I believe adding appropriate documentation would help users better understand what they are doing and avoid such pitfalls.

[sunyuhan1998]

Hi @ilayaperumalg what do you think of this?

[yuluo-yx]

LGTM

BTW, I think this can solve the problem you are facing now, or we can also solve it through configuration?

such as spring.main.web-application-type=reactive.
Should this be added to the documentation?

[sunyuhan1998]

BTW, I think this can solve the problem you are facing now, or we can also solve it through configuration?

such as spring.main.web-application-type=reactive. Should this be added to the documentation?

Yes, we can indeed solve this issue through this configuration. I had also considered documenting this configuration, but ultimately, I thought that if users are using other components in their projects that depend on WebMvc, applying this configuration might lead to some unintended side effects. Therefore, the best approach may be to guide users to use the appropriate Starter, rather than using spring-ai-starter-mcp-server-webflux in a WebMvc project, since doing so would be meaningless.