Question

When my Grails application starts, I build up a data structure from a CSV file downloaded from a remote URL. If the file is not accessible, I’d like to fall back to a local copy. Currently processing the file in the service layer, initiated using a Quartz job.

What is the best practice, using Groovy, for reading a local resource in Grails?

• Where should I stash the file?
• How do I safely and properly read the file?

General-case answers will be very acceptable.

Answer 1

I think the best way to deal with this is to store the file’s location in an externalized configuration file.

So, you’d determine a standardized location (such as /etc/myappname/CSVFileConfig.groovy), or pass the config file path in using an environment variable or something similar. See Externalized Configuration for examples.

Then you can simply add the actual path to the local file to that extenal config, like so:

// CSVFileConfig.groovy
my.custom.csv.path = ...

Finally, access it using normal config operations:

// in your Quartz job
def path = grailsApplication.config.my?.custom?.csv?.path
if(!path) {
    // no file to load
} else {
    // load file
}

As far as reading the file, what are your primary concerns? If you are using a CSV library, such as OpenCSV (used in most of the Grails libraries for CSV parsing), it will handle the opening and parsing of the file.

For security issues beyond that, I’m not sure how to handle them in a generic way. It will depend on your specific scenario. I think the one coming from a URL has a higher risk factor.