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Chapter

17

TML forms, discussed in Chapter 16, provide a simple but limited

way of collecting user input and transmitting it to a servlet or CGI

H

program. Occasionally, however, a more sophisticated user interface

is required. Applets give you more control over the size, color, and font of the

GUI controls; provide more built in capability (sliders, line drawing, pop up

windows, and the like); let you track mouse and keyboard events; support the

development of custom input forms (dials, thermometers, draggable icons,

and so forth); and let you send a single user submission to multiple

server side programs. This extra capability comes at a cost, however, as it

tends to require much more effort to design an interface in the Java program 

ming language than it does using HTML forms, particularly if the interface

contains a lot of formatted text. So, the choice between HTML forms and

applets will depend upon the application.

With HTML forms, 

GET

 and 

POST

 requests are handled almost exactly

the same way. All the input elements are identical; only the 

METHOD

attribute of the 

FORM

 element needs to change. With applets, however,

there are three distinct approaches. In the first approach, covered in Sec 

tion 17.1, the applet imitates a 

GET

 based HTML form, with 

GET

 data being

transmitted and the resultant page being displayed by the browser. Section

17.2 (A Multisystem Search Engine Front End) gives an example. In the

second approach, covered in Section 17.3, the applet sends 

GET

 data to a

servlet and then processes the results itself. Section 17.4 (A Query Viewer

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