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what is screen scraper?

 
air lulu
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i meet the question in "Sun Certified Enterprise Arthitect for J2EE Study Guide".
14. Which of the following are not true about screen scrapers?
A. Screen scrapers function as terminal emulators on one end and as object interfaces on
the other.
B. Screen scraping may be a useful tool when used in conjunction with the off-board servers.
C. Changes to legacy UI has little or no impact on the new GUI.
D. Screen Scraping is best used when the legacy clients have loose coupling with other tiers.

the correct answer is C and D.
but i don't know what "screen scraper" is,does anyone help me?
 
Muhammad Asif
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Screen Scrapers
Screen scrapers may be used to integrate applet (or other) interface with an existing system. They are particularly useful when the client interface is tightly coupled to the other tiers of the system.
A screen scraper is an application that translates an existing client interface into a set of objects. Screen scrapers usually function as a terminal emulator on one end and an object interface on the other. The screen scraper is configured to read data from terminal fields of the legacy interface and make them available via objects.
Screen scrapers have the following advantages:
�Provides a low-level object-based interface to the legacy app.
�Allows you to build a new GUI over the existing client interface.
Disadvantages of screen scrapers:
�Any changes to the legacy interface can break the new GUI.
�Prone to causing errors in the new GUI because of unexpected outputs from the legacy interface.
�Prone to causing the new GUI to �freeze� when the legacy interface is expecting input that the screen scraper in unaware of.


"Credits to LeoCrawford for her Notes."
 
air lulu
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thank you for your reply!!
very helpful
 
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