An XQuery Servlet for RESTful Data Services

Overview of Tutorial:

Many web applications exchange data as XML, but that data is usually stored in and queried from relational databases, CRM, ERP, proprietary repositories, and a hodgepodge of other systems. Unfortunately, the languages most commonly used for creating or processing data on the web were designed neither for processing XML nor for integrating data among multiple heterogeneous sources. These are precisely the tasks for which the XQuery language was designed.

This paper shows how to use XQuery for data integration, and how to expose an XQuery as a RESTful data service using a Java servlet. Listing 1 contains the source code for the servlet. This servlet uses the name and external variables of any XQuery to provide a REST interface to the query and deploys the query.

As an XML-oriented data integration language, XQuery can be used to access XML, relational, and flat file formats such as EDI to create complex XML and HTML results. To deploy a query, a developer saves the query into a designated deployment directory in a secure location accessible to the servlet. Subsequently, developers can invoke any query in this directory using its REST interface, which requires nothing more than an HTTP GET or POST operation using a URL that represents the query and its parameters.

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