Package org.apache.juneau.rest.server.mcp

Class AbstractMcpRestServlet

java.lang.Object
jakarta.servlet.GenericServlet
jakarta.servlet.http.HttpServlet
org.apache.juneau.rest.server.servlet.RestServlet
org.apache.juneau.rest.server.servlet.BasicRestServlet
org.apache.juneau.rest.server.mcp.AbstractMcpRestServlet
All Implemented Interfaces:
jakarta.servlet.Servlet, jakarta.servlet.ServletConfig, Serializable, BasicUniversalConfig, DefaultConfig, DefaultHtmlConfig, ReadinessStateAware
Direct Known Subclasses:
McpRestServlet, McpRestServlet
public abstract class AbstractMcpRestServlet extends BasicRestServlet implements ReadinessStateAware
Drop-in BasicRestServlet subclass that exposes a single MCP JSON-RPC endpoint at POST /.

Subclasses provide their McpServerConfig by overriding createMcpConfig() (called once at init time), or by registering an McpServerConfig bean in their RestContext bean store.

Example:











    


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    Constructor Details
    


    

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    Method Details
    

      

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      getMcpConfig
      

      public McpServerConfig getMcpConfig()
      

      Returns the McpServerConfig backing this servlet.

 
      
 The default implementation lazily caches the value of createMcpConfig(); subclasses needing
 per-request reconfiguration may override.

 
      
 This is invoked on every request, so the cache is published via a lock-free AtomicReference.compareAndSet(V, V)
 rather than a synchronized block, avoiding monitor contention on the hot path. Under a first-access
 race, createMcpConfig() may be invoked by more than one thread, but only one resulting instance is
 ever published to config and returned to any caller; the others are discarded. This is safe as long
 as createMcpConfig() is side-effect-free and idempotent (i.e. simply constructs and returns a new
 config), which is the documented contract of that method.
      

      

      Returns:
      

      The config. Never null.
      

      

      

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      createMcpConfig
      

      protected abstract McpServerConfig createMcpConfig()
      

      Factory method for the McpServerConfig backing this servlet.

 
      
 Subclasses must override this method to declare their tools, prompts, and resources.
      

      

      Returns:
      

      A non-null server config.
      

      

      

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      revision
      

      protected abstract McpRevision revision()
      

      The MCP protocol revision this servlet speaks.

 
      
 Supplied by the revision-specific subclass a consumer extends (for example
 org.apache.juneau.rest.server.mcp.v20250618.McpRestServlet); consumers do not normally implement this themselves.
      

      

      Returns:
      

      The bound revision. Never null.
      

      

      

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      getSubscriptionBroker
      

      protected McpSubscriptionBroker getSubscriptionBroker()
      

      Optional subscription broker backing this servlet's subscriptions/listen support.

 
      
 Returning null (the default) means this servlet does not support subscriptions: no
 McpSubscriptionBroker or McpSubscriptions bean is added to the request-scoped
 BeanStore that handleMcp(org.apache.juneau.bean.jsonrpc.JsonRpcRequest, org.apache.juneau.rest.server.RestRequest) builds, so any handler or dispatch branch that looks one up
 via ctx.getBean(McpSubscriptionBroker.class) sees Optional.empty().

 
      
 A revision binding that implements subscriptions/listen (for example
 org.apache.juneau.rest.server.mcp.v20260728.McpRestServlet) overrides this to return a
 memoized broker instance so every request sees the same live subscription registry.
      

      

      Returns:
      

      The subscription broker, or null if this servlet does not support subscriptions.
      

      

      

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      acceptReadinessState
      

      public void acceptReadinessState(ReadinessState state)
      

      Closes this servlet's open subscription streams as soon as the embedded server begins shutting down.

 
      
 A subscriptions/listen stream never finishes on its own, so without this the server's graceful
 drain would wait out its entire stop timeout (30s by default) for every connected subscriber before it
 could stop.  Closing the subscriptions makes each stream send its terminal frame and complete, letting
 the drain finish immediately.
      

      

      Specified by:
      

      acceptReadinessState in interface ReadinessStateAware
      

      Parameters:
      

      state - The per-service readiness state published by the embedded-server lifecycle component.
      

      

      

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      handleMcp
      

      public Object handleMcp(@Content
 JsonRpcRequest req,
 RestRequest restReq)
      

      MCP JSON-RPC endpoint.
      

      

      Parameters:
      

      req - The parsed JSON-RPC request envelope.
      

      restReq - The HTTP request (used to surface the bean store to handlers).
      

      Returns:
      

      The JSON-RPC response, or null for notifications (which the framework renders as an
         empty body).
      

      

      

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