MCP Java SDK Release Notes

Breaking Changes ⚠️

Follow the 0.8.0 Migration Guide for the new API changes.

Features & Enhancements

Architecture Improvements

Introduced session-based architecture for MCP server to better handle multiple concurrent client connections (#31)
- Added McpServerTransportProvider interface to manage client connections
- Introduced exchange objects (McpAsyncServerExchange, McpSyncServerExchange) for client interaction
- Updated handler signatures to include exchange parameter
- Renamed various interfaces and classes for better alignment with MCP specification
- Added migration guide (migration-0.8.0.md) for transitioning to the new architecture

API Improvements

Added builder pattern for CreateMessageRequest, improving usability and readability when creating message requests (#60)
Relaxed MCP Schema JSON deserialization constraints by adding @JsonIgnoreProperties(ignoreUnknown = true) to all record classes, improving compatibility with third-party implementations (#37)

Client Enhancements

Improved initialization state handling in McpAsyncClient with proper state tracking using AtomicBoolean and Sinks (#39)
Added OSGi metadata generation support using bnd-maven-plugin to enable proper OSGi bundle creation (#10)

Build & Deployment

Enabled automatic publishing to Maven Central when releases are performed (#63)

Bug Fixes

Protocol Compliance

Fixed CreateMessageRequest includeContext enum values to match MCP specification (changed from snake_case to camelCase) (#44)
Converted StopReason enum values from snake_case to camelCase for consistency (#58)

Connection & Session Management

Fixed issue where SSE connection would terminate after 30 seconds (DEFAULT) (#21)
Removed closed sessions from list in WebMvcSseServerTransport to prevent errors when broadcasting to outdated sessions (#19)
Fixed issue where resources and prompts could not be added after server start (#18)

Testing & Reliability

Improved client test reliability and execution time using VirtualTimeScheduler (#52)
Fixed duplicated connection to testcontainer MCP server in client tests (#54)
Synced async client tests between mcp and mcp-test modules (#55)

Refactoring & Code Quality

Client Improvements

Improved MCP client timeout handling with configurable initialization timeout separate from request timeout (#51)
Enhanced validation and removed server-side notification methods from client (#14)
Removed redundant type field from Content implementations (#27)

Documentation Updates

Added Spring AI MCP documentation section with links to client/server starters (#12)
Updated README with Maven wrapper commands and test prerequisites (#23)
Fixed build status badge in README (#50)
Fixed various typos throughout the codebase (#22)
Made closeLatch a final field (#32)

Contributors

Christian Tzolov (@tzolov)
Dariusz Jędrzejczyk (@chemicL)
Jermaine Hua (@CrazyHZM)
Piotr Roterski (@roterski)
Dennis Kawurek (@denniskawurek)
Mariano Gonzalez (@marianogonzalez)
zeko zhang (@zekozhang)
konczdev (@konczdev)
He-Pin(kerr) (@He-Pin)

What's Changed Log

Refactor package structure and dependencies by @tzolov in #1
Change license from Apache to MIT by @tzolov in #3
Remove redundand code by @tzolov in #5
Reorder StdioServerTransport shutdown procedure to avoid errors by @chemicL in #7
Change the top domain from org to io by @tzolov in #8
Convert asciidoc/antora docs to mintlify by @markpollack in #6
docs: add Spring AI MCP documentation and improve README clarity by @tzolov in #12
Fix issue, SSE connection will terminate after 30 seconds (DEFAULT). by @zekozhang in #21
Remove closed sessions from list in WebMvcSseServerTransport by @denniskawurek in #19
Fix some typos by @CrazyHZM in #22
Resources and prompts cannot be added after server start by @marianogonzalez in #18
Add OSGi Metadata Generation by @konczdev in #10
refactor(client): improve validation and remove server methods by @tzolov in #14
Update README with Maven wrapper commands and test prerequisites by @tzolov in #23
refactor(mcp): remove redundant type field from Content implementations by @tzolov in #27
feat(mcp): relax MCP Schema JSON deserialization constraints by @tzolov in #37
feat(client): Improve initialization state handling in McpAsyncClient by @tzolov in #39
chore: Make closeLatch a final. by @He-Pin in #32
Add CI GitHub Action and rename snapshot publish workflow by @chemicL in #49
Update README.md by @tzolov in #50
refactor: improve MCP client timeout handling and reactive testing by @tzolov in #51
Improve client test reliability and execution time by @chemicL in #52
Follow-up fix client tests reliability by @chemicL in #54
Sync async client tests between mcp and mcp-test module by @chemicL in #55
refactor(McpSchema): convert StopReason enum values to camelCase by @tzolov in #58
feat(mcp): Add builder for CreateMessageRequest by @tzolov in #60
(pom) Enable automatic publishing to Maven Central by @tzolov in #63