I have a pdf file including form fields and need to export the data into a xml file AUTOMATICALLY. Here is a screen of a sample form I created for testing:

Note: It works great exporting it MANUALLY using Acrobat Professional by clicking on Tools > Form > Export Form Data and finally chose xml extension for file output. This is the result I'm getting when I export it manually:
<?xml version="1.0" encoding="UTF-8"?>
<fields>
<first_name>John</first_name>
<last_name>Doe</last_name>
</fields>
However, I need to automate it, e.g. with a python script, Java implementation or some command line tools. Any ideas which libraries or tools I could use to export form field data to xml? The tool or library should be open source, that I can integrate it in my workflow.
I already tried python pdfminer library, which helped me to export static parts (like Static form header, First name: and Last name:) of the pdf file: But how to export form field data (in my case the content of the form fields first_name and last_name)??
EDIT: Feel free to download the sample.pdf file here.