Extension Modules - eXist: A NoSQL Database and Application Development Platform - page 127

CHAPTER 7
Extension Modules
eXist has a large number of extension modules built in that allow you to do lots of
wonderful things that you can't do with straight XQuery, such as manipulating the
database's content, inspecting an HTTP request, encrypting/decrypting data, and
performing XSLT transformations. This chapter will provide you with an overview of
the module mechanism in general. An overview of the available modules can be
found in Appendix A .
Types of Extension Modules
Extension modules come in two flavors, which you need to be aware of because they
behave differently in eXist. The module descriptions in Extension Module Descrip‐
tions will tell you the module type. We will also explain how to find out the module
type yourself in “Enabling Extension Modules” on page 128 .
Extension Modules Written in Java
Extension modules written in Java are fully integrated into eXist. You don't even have
to put an import module statement in your XQuery code to be able to use them. Most
of the eXist core functionality you use regularly is Java-backed (e.g., xmldb , request ,
transform , response , and util ).
For instance, when you want to find out the eXist home directory by calling
system:get-exist-home , you can simply do this in your code without an import
module statement for the system module. However, it is generally considered good
practice to have this explicitly set out, so you may choose to add, for example:
import module namespace system="http://exist-db.org/xquery/system";