Objective 3.1: Distinguish appropriate from inappropriate techniques for providing access to a legacy system from Java code given an outline description of that legacy system

Screen Scraper

Scenario:
You need to connect to a legacy mainframe system. The source code is not available, the database cannot be accessed directly.

Possible architecture:
Build a screenscraper to emulate the legacy system's terminal.

Pros:

  • Requires not a lot of effort to implement
  • Low-level object-based interface to the legacy system
  • Allows you to build a new GUI over the existing client interface
  • Can be implemented without any disruption to existing legacy applications

Cons:

  • Slow
  • Scalability might be a problem, because the original system may not be able to handle the load inflicted by the J2EE application.
  • Changing the mainframe code might make the scraper stop working
  • Does not allow for adding new functionality
  • Unexpected outputs or expected inputs that the new GUI is unaware of can cause the new GUI to freeze or break

Screen Scraper
A Screen Scraper is an application that translates an existing client interface into a set of objects.