Feature: McpTransportContext for HttpServletSseServerTransportProvider

[stantonk]

Implements #476.

Motivation and Context

#420 introduced McpTransportContext.

McpTransportContext should be supported in HttpServletSseServerTransportProvider to enable those who are still on that transport to leverage McpTransportContext to set attributes that Tools, etc. have access to. This is crucial for implementing Authentication & Authorization at the Tool level.

Current Behavior

McpTransportContext is absent from HttpServletSseServerTransportProvider

Context

How has this issue affected you?

We're not able to switch to HttpServletStreamableServerTransportProvider yet, but wish to use McpTransportContext instead of our custom built similar capability.

What are you trying to accomplish?

Authn/z at Tool level.

How Has This Been Tested?

• In a langchain4j agent application calling into a Dropwizard application serving MCP using HttpServletSseServerTransportProvider
• directly by testing a Dropwizard application serving MCP using HttpServletSseServerTransportProvider
• Integration tests included with PR

Breaking Changes

No, use of the McpTransportContext is optional.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

None

[chemicL]

Thanks, I think this is useful and seems you found a way around the singleton behaviour of the exchange object :) Left some comments to improve a few things, but I agree we should merge this once fixed. Also, would you consider following up with the Spring-related SSE transport providers to maintain feature parity?

[stantonk]

@chemicL thanks for the quick review! All your suggestions make sense, I'll get those updates made.

RE: Spring support, I've never used Spring but I can take a pass at it, probably this weekend. If I hit some snags would you be open to merging the Servlet version in first? I just don't want to stay on our internal fork for too long as additional capabilities and bug fixes get merged in.

[stantonk]

@chemicL thanks again for the review!

Updates

• I've made all your recommended updates

Testing

• I re-ran mvn clean verify locally and all tests passed
• I ran mvn clean install locally, and configured our Dropwizard MCP Service to use the latest HEAD of this PR after all your requested changes. I confirmed our AI Agent service talking to our Dropwizard MCP Service is functioning properly with the latest changes, including our Authentication & Authorization into the individual MCP Tool call level via the McpTransportContextExtractor using HttpServletSseServerTransportProvider. Initialization, list tools, and tool calls are working properly.

Spring WebMvc and WebFlux

I took a quick look through the code, it all looks pretty similar so I should be able to follow up in a subsequent PR adding McpTransportContext to those as well. I've got a busy week coming up, but I'll try for next weekend.