feat: add a2a routes to existing app

src/a2a/server/apps/jsonrpc/fastapi_app.py

@@ -23,51 +23,47 @@
     (SSE).
     """
 
     def __init__(
         self,
         agent_card: AgentCard,
         http_handler: RequestHandler,
         extended_agent_card: AgentCard | None = None,
         context_builder: CallContextBuilder | None = None,
     ):
         """Initializes the A2AStarletteApplication.
 
         Args:
             agent_card: The AgentCard describing the agent's capabilities.
             http_handler: The handler instance responsible for processing A2A
               requests via http.
             extended_agent_card: An optional, distinct AgentCard to be served
               at the authenticated extended card endpoint.
             context_builder: The CallContextBuilder used to construct the
               ServerCallContext passed to the http_handler. If None, no
               ServerCallContext is passed.
         """
         super().__init__(
             agent_card=agent_card,
             http_handler=http_handler,
             extended_agent_card=extended_agent_card,
             context_builder=context_builder,
         )
 
-    def build(
+    def add_routes_to_app(
         self,
+        app: FastAPI,
         agent_card_url: str = '/.well-known/agent.json',
         rpc_url: str = '/',
         extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
-        **kwargs: Any,
-    ) -> FastAPI:
-        """Builds and returns the FastAPI application instance.
+    ) -> None:
+        """Adds the routes to the FastAPI application.
 
         Args:
+            app: The FastAPI application to add the routes to.
             agent_card_url: The URL for the agent card endpoint.
             rpc_url: The URL for the A2A JSON-RPC endpoint.
             extended_agent_card_url: The URL for the authenticated extended agent card endpoint.
-            **kwargs: Additional keyword arguments to pass to the FastAPI constructor.
-
-        Returns:
-            A configured FastAPI application instance.
         """
-        app = FastAPI(**kwargs)
 
         @app.post(rpc_url)
         async def handle_a2a_request(request: Request) -> Response:
@@ -85,4 +81,28 @@
                     request
                 )
 
+    def build(
+        self,
+        agent_card_url: str = '/.well-known/agent.json',
+        rpc_url: str = '/',
+        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        **kwargs: Any,
+    ) -> FastAPI:
+        """Builds and returns the FastAPI application instance.
+
+        Args:
+            agent_card_url: The URL for the agent card endpoint.
+            rpc_url: The URL for the A2A JSON-RPC endpoint.
+            extended_agent_card_url: The URL for the authenticated extended agent card endpoint.
+            **kwargs: Additional keyword arguments to pass to the FastAPI constructor.
+
+        Returns:
+            A configured FastAPI application instance.
+        """
+        app = FastAPI(**kwargs)
+
+        self.add_routes_to_app(
+            app, agent_card_url, rpc_url, extended_agent_card_url
+        )
+
         return app

src/a2a/server/apps/jsonrpc/starlette_app.py

@@ -92,6 +92,28 @@ def routes(
             )
         return app_routes
 
+    def add_routes_to_app(
+        self,
+        app: Starlette,
+        agent_card_url: str = '/.well-known/agent.json',
+        rpc_url: str = '/',
+        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+    ) -> None:
+        """Adds the routes to the Starlette application.
+
+        Args:
+            app: The Starlette application to add the routes to.
+            agent_card_url: The URL path for the agent card endpoint.
+            rpc_url: The URL path for the A2A JSON-RPC endpoint (POST requests).
+            extended_agent_card_url: The URL for the authenticated extended agent card endpoint.
+        """
+        routes = self.routes(
+            agent_card_url=agent_card_url,
+            rpc_url=rpc_url,
+            extended_agent_card_url=extended_agent_card_url,
+        )
+        app.routes.extend(routes)
+
     def build(
         self,
         agent_card_url: str = '/.well-known/agent.json',
@@ -110,14 +132,10 @@ def build(
         Returns:
             A configured Starlette application instance.
         """
-        app_routes = self.routes(
-            agent_card_url=agent_card_url,
-            rpc_url=rpc_url,
-            extended_agent_card_url=extended_agent_card_url,
+        app = Starlette(**kwargs)
+
+        self.add_routes_to_app(
+            app, agent_card_url, rpc_url, extended_agent_card_url
         )
-        if 'routes' in kwargs:
-            kwargs['routes'].extend(app_routes)
-        else:
-            kwargs['routes'] = app_routes
 
-        return Starlette(**kwargs)
+        return app