Job Management System within existing Java Web Application

Background: Our web-based software provides marketing automation functions for a number of clients. Although web-accessible, the system is only used by contracted clients and is not publicly available. We are looking to enhance the existing functionality by adding a new job management workflow. We have an existing Java servelet based web application, running on Apache Tomcat 5.5 and Java 6. The database used is MySQL 4.1 and there are a number of dependencies on some older open-source and proprietary libraries. The framework used is a proprietary modification of Struts v1 (MVC based) and the source code is not available for a number of the proprietary libraries used. Warning: previous developers have said the existing system takes quite a bit of getting used to. While the functionality provided by the existing system is fairly straight forward, it is often implemented in specific ways and attempts to deviate from the existing frameworks are not successful. Current Task: The new development is based around a new job tracking system. The jobs will be stored in the MySQL database (for information fields) and in Binary Form (for file attachments). There are a few basic job-types to be tracked, each with their own mandatory form fields. This will require validation of the input, both server-side and via Javascript for the end-user. Ideally, some AJAX libraries will be used to facilitate uploads of (potentially) large files, and a series of e-mail alerts will also be required. Integration with the credit card payments system will also be required (via existing payments service). We have a specifications document for this development, which includes descriptions of the form fields and their requirements. We can provide you with access to this document, once you have signed our Non-Disclosure Agreement. A "Business Requirements" document is also available to provide further background information.