Client-Side Implementation of Client Streaming RPC

In this lesson we show the client side implementation of the client streaming addFile RPC. The client side is implemented in the ftp-service-client module and it is called using the ftp-service-cli-client module.

addFile method in FTPServiceClient class

The addFile method is used to transfer a file from the local system to the server’s destination directory. It contains the logic of breaking down larger files into chunks and computing checksums to ensure data integrity during transmission. Each chunk of the file is sent as a separate message. Open the FTPServiceClient class from the src/main/java/io/datajek/ftpservice/client package in the ftp-service-client module. We will write the addFile method in this class for the client-side implementation of the add file RPC.

The method will take three input parameters:

• sourceFilePath: This represents the source file that we want to send to the server. This represents the name of the file in the local file system.

• destFileName: This specifies the name that the file should have in the server’s destination directory. It is the desired name for the file on the server.

• resultStreamObserver: The StreamObserver callback interface allows us to handle messages asynchronously and receive status updates and the final result of the add file operation. The Result object contains information about the status of the file transfer. resultStreamObserver is the observer that the client provides when making a call to the server. It’s used by the server to send responses back to the client.

The server-side implementation of addFile discussed in the previous lesson has another observer, StreamObserver<AddFileRequest>, which is used by the server to receive client requests. Compare this to the implementation of the deletefile method, which only required the resultStreamObserver.

Flow diagram

The diagram below shows the steps of sending a file to the server.

We first create a StreamObserver for sending the stream of messages to the server. The StreamObserver has three methods which we will override.

• The onNext method is used to send the file metadata and file chunks.

• The ...