Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.
2.2 A Simple Servlet Generating Plain Text
25
3. A directory for infrequently changing servlets in JAR files. 
With the second option above, the class files are placed directly 
in the 
classes
 directory or in subdirectories corresponding to 
their package name. Here, the class files are packaged in a JAR 
file, and that file is then placed in the designated directory. With 
Tomcat, the JSWDK, the Java Web Server, and most other serv 
ers, this directory is 
install_dir/lib
. You must restart the 
server whenever you change files in this directory.
Once you've configured your server, set your 
CLASSPATH
, and placed the
servlet in the proper directory, simply do  
javac HelloWorld.java
  to
compile the servlet. In production environments, however, servlets are fre 
quently placed into packages to avoid name conflicts with servlets written by
other developers. Using packages involves a couple of extra steps that are
covered in Section 2.4 (Packaging Servlets). Also, it is common to use HTML
forms as front ends to servlets (see Chapter 16). To use them, you'll need to
know where to place regular HTML files to make them accessible to the
server. This location varies from server to server, but with the JSWDK and
Tomcat, you place an HTML file in
install_dir/webpages/path/file.html
 and then access it via
http://localhost/path/file.html
 (replace 
localhost
 with the real
hostname if running remotely). A JSP page can be installed anywhere that a
normal HTML page can be.
Invoking the Servlet
With different servers, servlet classes can be placed in a variety of different
locations, and there is little standardization among servers. To invoke servlets,
however, there is a common convention: use a URL of the form
http://host/servlet/ServletName
. Note that the URL refers to 
serv 
let
, singular, even if the real directory containing the servlet code is called
servlets
, plural, or has an unrelated name like 
classes
 or 
lib
. 
Figure 2 1, shown earlier in this section, gives an example with the Web
server running directly on my PC ( localhost  means  the current machine ). 
Most servers also let you register names for servlets, so that a servlet can
be invoked via 
http://host/any path/any file
. The process for doing
this is server specific; check your server's documentation for details. 
Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.
Servlet and JSP training courses by book's author: courses.coreservlets.com.






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