How do I grab data from an API that returns files in xml or json?

I'm working with a couple APIs for some needed data. One returns files in JSON and the other in xml. How do I then take that and either store the data in a format such as csv files for later use in a data store (I'm downloading a lot of data)? With the API that returns XML I can grab only one day of data at a time and I need to grab ~10 years worth of data. With the other API that returns data in json I can download roughly a years worth of data at a time and again I need to download about 10 years worth.

[Paolo]

Have you tried using the following functions:

jsondecode for json

and xml2struct for xml ?