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How to Add an API v2 Route

Write SPARQL templates

Add any SPARQL templates you need to src/main/twirl/queries/sparql/v2, using the Twirl template engine.

Write Responder Request and Response Messages

Add a file to the org.knora.webapi.messages.v2.responder package, containing case classes for your responder's request and response messages. Add a trait that the responder's request messages extend. Each request message type should contain a UserADM.

Request and response messages should be designed following the patterns described in JSON-LD Parsing and Formatting. Each responder's request messages should extend a responder-specific trait, so that ResponderManager will know which responder to route those messages to.

Write a Responder

Write an Akka actor class that extends org.knora.webapi.responders.Responder, and add it to the org.knora.webapi.responders.v2 package.

Give your responder a receive(msg: YourCustomType) method that handles each of your request message types by generating a Future containing a response message.

Add the path of your responder to the org.knora.webapi.responders package object, and add code to ResponderManager to instantiate the new responder. Then add a case to the receive method in ResponderManager, to match messages that extend your request message trait, and pass them them to that responder's receive method. The responder's resulting Future must be passed to the ActorUtil.future2Message. See Futures with Akka and Error Handling for details.

Write a Route

Add a class to the org.knora.webapi.routing.v2 package for your route, using the Akka HTTP Routing DSL. See the routes in that package for examples. Typically, each route route will construct a responder request message and pass it to RouteUtilV2.runRdfRouteWithFuture to handle the request.

Finally, add your route's knoraApiPath function to the apiRoutes member variable in KnoraService. Any exception thrown inside the route will be handled by the KnoraExceptionHandler, so that the correct client response (including the HTTP status code) will be returned.

Last update: January 19, 2023