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Implement a simple transfer listener

In this sample, we build upon the file transfer sample to add functionality to react to transfer completion on the consumer connector side.

We will use the provider from the file transfer sample, and the consumer built on the consumer from that sample, with a transfer process listener added.

Also, in order to keep things organized, the code in this example has been separated into several Java modules:

  • consumer: this is where the extension definition and dependencies reside for the consumer connector
  • listener: contains the TransferProcessListener implementation

The consumer also uses the api module (REST API) from the file transfer sample.

Create the listener

A TransferProcessListener may define methods that are invoked after a transfer changes state, for example, to notify an external application on the consumer side after data has been produced (i.e. the transfer moves to the completed state).

// in TransferListenerExtension.java
    @Override
    public void initialize(ServiceExtensionContext context) {
        // ...
        var transferProcessObservable = context.getService(TransferProcessObservable.class);
        transferProcessObservable.registerListener(new MarkerFileCreator(monitor));
    }
public class MarkerFileCreator implements TransferProcessListener {

    /**
     * Callback invoked by the EDC framework when a transfer has completed.
     *
     * @param process
     */
    @Override
    public void completed(final TransferProcess process) {
        // ...
    }
}

Perform a file transfer

Let's rebuild and run them both:

./gradlew samples:04.1-file-transfer-listener:consumer:build
java -Dedc.fs.config=samples/04.1-file-transfer-listener/consumer/config.properties -jar samples/04.1-file-transfer-listener/consumer/build/libs/consumer.jar
# in another terminal window:
./gradlew samples:04.0-file-transfer:provider:build
java -Dedc.fs.config=samples/04.0-file-transfer/provider/config.properties -jar samples/04.0-file-transfer/provider/build/libs/provider.jar

Assuming you didn't change the config files, the consumer will listen on port 9191 and the provider will listen on port 8181. Open another terminal window (or any REST client of your choice) and execute the following REST requests like in the previous sample:

curl -X POST -H "Content-Type: application/json" -d @samples/04.0-file-transfer/contractoffer.json "http://localhost:9191/api/negotiation?connectorAddress=http://localhost:8181/api/ids/multipart"
curl -X GET -H 'X-Api-Key: password' "http://localhost:9191/api/control/negotiation/{negotiation ID}/state"
curl -X POST "http://localhost:9191/api/file/test-document?connectorAddress=http://localhost:8181/api/ids/multipart/&destination=/path/on/yourmachine&contractId={agreement ID}"

Replace {negotiation ID} in the second request with the UUID received as the response to the first request!

Copy the contract agreement's ID from the second response, substitute it for {agreement ID} in the last request and adjust the destination to match your local dev machine!

  • the last path item, test-document, matches the ID of the Asset that we created earlier in FileTransferExtension.java, thus referencing the data source
  • the first query parameter (connectorAddress) is the address of the provider connector
  • the last query parameter (destination) indicates the desired destination directory on you local machine.
  • curl will return the ID of the transfer process on the consumer connector.

The consumer should spew out logs similar to:

INFO 2021-09-07T17:24:42.128363 Received request for file test-document against provider http://localhost:8181/
DEBUG 2021-09-07T17:24:42.592422 Request approved and acknowledged for process: 2b0a9ab8-78db-4753-8b95-77678cdd9fc8
DEBUG 2021-09-07T17:24:47.425729 Process 2b0a9ab8-78db-4753-8b95-77678cdd9fc8 is now IN_PROGRESS
DEBUG 2021-09-07T17:24:47.426115 Process 2b0a9ab8-78db-4753-8b95-77678cdd9fc8 is now COMPLETED
DEBUG 2021-09-07T17:24:47.426531 Transfer listener successfully wrote file /path/on/yourmachine/marker.txt

then check /path/on/yourmachine, which should now contain a file named marker.txt in addition to the file named test-document.txt.