Claude
9919da58a7
Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01FtpJvZfg4nvLvtzgJTDWpB
36 lines
2.4 KiB
Plaintext
36 lines
2.4 KiB
Plaintext
# The 404 that shows up with no spring.ai.mcp.server.protocol set, and why
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Captured manually against a standalone run of this module with application.yml's
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`spring.ai.mcp.server.protocol: streamable` line removed -- everything else identical.
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Reproduced with: `mvn -o spring-boot:run --server.port=18099 --debug`, then:
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$ curl -X POST http://localhost:18099/mcp -H "Content-Type: application/json" \
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-H "Accept: application/json, text/event-stream" \
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-d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'
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{"timestamp":"2026-09-23T11:44:01.196Z","status":404,"error":"Not Found","path":"/mcp"}
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The real reason, from Boot's own --debug condition-evaluation report (trimmed to the one line
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that matters):
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McpServerStreamableHttpWebMvcAutoConfiguration:
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Did not match:
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- AllNestedConditions 1 matched 1 did not; NestedCondition on
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McpServerAutoConfiguration.EnabledStreamableServerCondition.StreamableEnabledCondition
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@ConditionalOnProperty (spring.ai.mcp.server.protocol=STREAMABLE) did not find
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property 'protocol'; NestedCondition on
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McpServerAutoConfiguration.EnabledStreamableServerCondition.McpServerEnabledCondition
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@ConditionalOnProperty (spring.ai.mcp.server.enabled=true) matched
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The jar's spring-configuration-metadata.json lists "streamable" as spring.ai.mcp.server.protocol's
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default value -- but that default is only ever applied when something actually binds the
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@ConfigurationProperties object (McpServerProperties). The @ConditionalOnProperty guarding
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McpServerStreamableHttpWebMvcAutoConfiguration runs before any binding happens, checking the
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Spring Environment directly for a literal "spring.ai.mcp.server.protocol" entry. No entry, no
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match, no RouterFunction registered for /mcp -- the endpoint simply does not exist, and every
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request to it 404s exactly like a request to a path nobody ever mapped, which is exactly what it
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is. Setting spring.ai.mcp.server.protocol: streamable explicitly in application.yml fixes it, and
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that same run then returns a normal 200 with a real MCP initialize response, e.g.:
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{"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2025-06-18","capabilities":{"completions":{},"logging":{},"prompts":{"listChanged":true},"resources":{"subscribe":false,"listChanged":true},"tools":{"listChanged":true}},"serverInfo":{"name":"order-lookup-server","version":"1.0.0"}}}
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