File Store Access

The file store access through SFTP is now configurable, allowing the user to pick a supporting library to upload and delete files in the file store.

History

The original version of the Clarity Client used spring-integration-sftp directly in the client to access the file store. This at the time used JCraft's JSch library to do the low level SSH communication. The update for this second version of the Clarity Client moved the dependency on to Spring Integrations 6.3 and with it a change from JSch under the hood to Apache Mina SSHD. This should have been almost invisible, hiding the detail behind the Spring wrapper of DefaultSftpSessionFactory.

All so far so good: there were some changes to the dependencies but it should work. Except of course it didn't. We found Apache Mina to behave very strangely, timing out accessing a server where we knew that the SSH daemon was running and we had the correct credentials. Indeed, the command line sftp program worked as did the same test in JSch.

To this end, the SFTP access to the file store has been abstracted away from the client's code and put into classes that implement the new ClaritySFTPUploader interface. Implementations are provided for Apache Mina and for JSch.

It is recommended to use Apache Mina SSHD if you can, as it is up to date whereas JSch is very old now. If you have time out problems with Mina SSHD but the server is accessible by other tools, then try switching to the JSch implementation.

Picking an Implementation

Apache Mina

Add the clarity-client2-sftp-mina artefact to your project.

<dependency>
    <groupId>org.cruk.clarity</groupId>
    <artifactId>clarity-client2-filestore-mina</artifactId>
    <scope>runtime</scope>
</dependency>

This artefact will bring in the dependencies org.apache.sshd:sshd-osgi and org.apache.sshd:sshd-sftp.

JCraft JSch

Add the clarity-client2-sftp-jsch artefact to your project.

<dependency>
    <groupId>org.cruk.clarity</groupId>
    <artifactId>clarity-client2-filestore-jsch</artifactId>
    <scope>runtime</scope>
</dependency>

This artefact will bring in the dependency com.jcraft:jsch.

No Implementation

It should be noted that the client should work for uploading and downloading files to and from the file store without SFTP access, instead sending uploads through the Clarity API's file upload mechanism. There are however some advantages of SFTP access:

The uploads can take place after a process has been completed. The HTTP mechanism won't let files be uploaded to completed processes.
Files can be deleted from the file store. There isn't a mechanism for doing this through HTTP (to my knowledge).

If your code does not to upload files to or delete files from the file store, it would be sensible not to include either SFTP file store implementation.