Standardization of the XMLHttpRequest Object: The XMLHttpRequest object is not yet part of the JavaScript technology specification, which means that the behavior may vary depending on the client.
JavaScript Technology Implementations: AJAX interactions depend heavily on JavaScript technology, which has subtle differences depending on the client. See QuirksMode.org for more details on browser-specific differences.
Debugging: AJAX applications are also difficult to debug because the processing logic is embedded both in the client and on the server.
Viewable Source: The client-side JavaScript technology may be viewed simply by selecting View Source from an AJAX-enabled HTML page. A poorly designed AJAX-based application could open itself up to hackers or plagiarism.
Frameworks and patterns for AJAX technology are likely to emerge as developers gain more experience writing applications that use the AJAX interaction model. It is still early to focus on a one-size-fits-all framework for AJAX interactions. This article and the associated solutions focus on how AJAX interactions can be supported today by existing Java 2 Platform, Enterprise Edition (J2EE) technologies such as servlets, JavaServer Pages (JSP) software, JavaServer Faces applications, and the Java Standard Tag Libraries (JSTL).
