Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

3.3 Example: Reading Three Explicit Parameters

67

Core Warning

The values supplied to 

getParameter

 and 

getParameterValues

are case sensitive.

Finally, although most real servlets look for a specific set of parameter

names, for debugging purposes it is sometimes useful to get a full list. Use

getParameterNames

 to get this list in the form of an 

Enumeration

, each

entry of which can be cast to a 

String

 and used in a 

getParameter

 or 

get 

ParameterValues

 call. Just note that the 

HttpServletRequest

 API

does not specify the order in which the names appear within that 

Enumer 

ation

. 

Core Warning

Don't count on 

getParameterNames

 returning the names in any 

particular order.

3.3 Example: Reading Three 

Explicit Parameters

Listing 3.1 presents a simple servlet called 

ThreeParams

 that reads form

data parameters named 

param1

, 

param2

, and 

param3

 and places their val 

ues in a bulleted list. Listing 3.2 shows an HTML form that collects user

input and sends it to this servlet. By use of an 

ACTION

 of 

/servlet/core 

servlets.ThreeParams

, the form can be installed anywhere on the system

running the servlet; there need not be any particular association between the

directory containing the form and the servlet installation directory. Recall

that the specific locations for installing HTML files vary from server to

server. With the JSWDK 1.0.1 and Tomcat 3.0, HTML pages are placed

somewhere in 

install_dir/webpages

 and are accessed via

http://host/path/file.html

. For example, if the form shown in Listing

3.2 is placed in 

install_dir/webpages/forms/ThreeParams 

Form.html

 and the server is accessed from the same host that it is running

on, the form would be accessed by a URL of 

http://local 

host/forms/ThreeParamsForm.html

.

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

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