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17.2 A Multisystem Search Engine Front End

435

encode the value of each entry, but not the equal sign (=) between each entry

name and its value or the ampersand (&) between each name/value pair. So,

you cannot necessarily simply call 

URLEncoder.encode(someData)

 but

instead need to selectively encode the value parts of each name/value pair. This

could be accomplished as follows:

String someData =

name1 + "=" + URLEncoder.encode(val1) + "&" +

name2 + "=" + URLEncoder.encode(val2) + "&" +

...

nameN + "=" + URLEncoder.encode(valN);

try {

URL programURL = new URL(baseURL + "?" + someData);

getAppletContext().showDocument(programURL);

} catch(MalformedURLException mue) { ... }

The following section gives a full fledged example.

17.2 A Multisystem Search Engine 

Front End

In Section 6.3 (A Front End to Various Search Engines), the 

SearchSpec

class (Listing 6.2) was used by a servlet to generate the specific URLs

needed to redirect requests to various different search engines. The

SearchSpec

 class can be used by applets as well. Listing 17.1 shows an

applet that creates a textfield to gather user input. When the user submits

the data, the applet URL encodes the textfield value and generates three

distinct URLs with embedded 

GET

 data: one each for the Google, Infoseek,

and Lycos search engines. The applet then uses 

showDocument

 to instruct

the browser to display the results of those URLs in three different frame

cells. The results are shown in Figures 17 1 and 17 2. HTML forms cannot

be used for this application since a form can submit its data to only a single

URL.

Listing 17.2 shows the top level HTML document used and Listing 17.3

shows the HTML used for the frame cell actually containing the applet.

Please refer to this book's Web site (

http://www.coreservlets.com/

) for

the three tiny HTML files used for the initial contents of the bottom three

frame cells shown in Figure 17 1. 

Home page for this book: www.coreservlets.com; Home page for sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.