...how to read a file programmatically in SwitchYard

I’ve been asked recently how to read a file programmatically, based on a cron, or when a request is made via a call to a Service. I didn’t have an answer, well, really I had an answer and I was wrong. Today, somebody brought the topic back, and I revisited the problem, and now I have an answer, one that works, so a good answer.

Problem description

I have the following use case:

A file should be downloaded by FTP from a remote server. The download of the file can be triggered in two ways:

• by a scheduler whose polling interval may be changed at runtime
• by a HTTP GET Request on a specified url. The response of the HTTP call must include transformed data based on the downloaded file.

What is a good way to achieve these requirements with SY/Camel? I would like to use the bindings provided by Camel, but have no idea how they can be triggered (e.g. the FTP binding) from outside the binding.

Solution

I have created a sample project, just to demonstrate how it works, not the full problem is solved. You have to use thecontent ennricher EIP.

We have a service, with a scheduled binding (Every 30 secs) that calls a Camel component. In this component, we use pollEnrich to read a file, and the use the contents of the file (the Message) to write into a File (a Reference with file binding).

This is the route we will be using. Note the pollEnrich to read the file.

public void configure() {
 from("switchyard://ProgramaticReload")
 .log("Going to read the file")
 .pollEnrich("file:///input?fileName=in.txt",1000)
 .log("Read from file : ${body}")
 .to("switchyard://FileWriterService");
}

The project is available in github