OK, so you have a development directory. You can compile servlets with or without
packages. You know which directory the servlet classes belong in. You know the URL
that should be used to access them. (Actually,
http://hostname/servlet/ServletName is just the default URL; you can also
use the web.xml file to customize that URL. Use of web.xml
is discussed in detail in Chapter 5 of
More Servlets and JavaServer Pages.) But how do you move the
class files from the development directory to the deployment directory?
Copying each one by hand every time is tedious and error prone. Once you
start using Web applications, copying individual files becomes even
more cumbersome.
There are several options to simplify the process. Here are a few of the most popular
ones. If you are just beginning with servlets and JSP, you probably want to start
with the first option and use it until you become comfortable with the development
process. Note that I do not list the option of putting your code directly in the server's
deployment directory. Although this is one of the most common choices among
beginners, it scales so poorly to advanced tasks that I recommend you steer clear of it
from the start.
- Copy to a shortcut or symbolic link.
- Use the
-d option of javac.
- Let your IDE take care of deployment.
- Use
ant or a similar tool.
Details on these four options are given below.
Go to install_dir/webapps/ROOT/WEB-INF, right-click on the classes
directory, and select Copy. Then go to your development directory, right-click, and
select Paste Shortcut (not just Paste). Now, whenever you compile a packageless
servlet, just drag the class files onto the shortcut.
When you develop in packages, use
the right mouse to drag the entire directory
(e.g., the moreservlets directory) onto
the shortcut, release the mouse, and select Copy. On Unix/Linux, you can use symbolic
links (created with ln -s) in a manner similar to that for Windows shortcuts.
An advantage of this approach is that it is simple. So, it is good for beginners who
want to concentrate on learning servlets and JSP, not deployment tools. Another
advantage is that a variation applies once you start using your own Web applications.
Just make a shortcut to install_dir/webapps
and copy the entire Web application
each time by using the right mouse to drag the directory that contains your
Web application onto this shortcut and selecting Copy.
One disadvantage of this approach is that it requires repeated copying if you use
multiple servers. For example, I usually have Tomcat, JRun, and ServletExec
on my desktop system and regularly test my code with all three servers.
A second disadvantage is
that this approach copies both the Java source code files and the class files to the
server, whereas only the class files are needed. This does not matter on your
desktop server, but when you get to the "real" deployment server, you won't want to
include the source code files.
By default, the Java compiler (javac) places
class files in the same directory as the
source code files that they came from. However,
javac has an option (-d) that lets
you designate a different location for the class files. You need only specify the
top-level directory for class files--javac will
automatically put packaged classes in
subdirectories that match the package names. So, for example,
I could compile the HelloServlet2 servlet as follows (line break
added only for clarity; omit it in real life).
javac -d install_dir/webapps/ROOT/WEB-INF/classes
HelloServlet2.java
You could even make a Windows batch file or Unix shell script or alias that makes
a command like servletc expand to
javac -d install_dir/.../classes.
See
http://java.sun.com/j2se/1.3/docs/tooldocs/win32/javac.html for more details on
-d and other javac options.
An advantage of this approach is that it requires no manual copying of class files.
Furthermore, the exact same command can be used for classes in different packages
since javac automatically puts the class files in a
subdirectory matching the package.
The main disadvantage is that this approach applies only to Java class files; it won't
work for deploying HTML and JSP pages, much less entire Web applications.
Most servlet- and JSP-savvy development environments (e.g., IBM WebSphere Studio,
Macromedia JRun Studio, Borland JBuilder) have options that let you tell the
IDE where to deploy class files for your project. Then, when you tell the IDE to
build the project, the class files are automatically deployed to the proper location
(package-specific subdirectories and all).
An advantage of this approach, at least in some IDEs, is that it can deploy HTML
and JSP pages and even entire Web applications, not just Java class files. A disadvantage
is that it is an IDE-specific technique and thus is not portable across systems.
Developed by the Apache foundation, ant is a tool
similar to the Unix make utility.
However, ant is written in the Java programming
language (and thus is portable)
and is touted to be both simpler to use and more powerful
than make. Many servlet
and JSP developers use ant for compiling and deploying.
The use of ant is especially
popular among Tomcat users and with those developing Web applications.
For general information on using ant, see
http://jakarta.apache.org/ant/manual/.
See
http://jakarta.apache.org/tomcat/tomcat-4.0-doc/appdev/processes.html
for specific guidance on using ant with Tomcat.
The main advantage of this approach is flexibility:
ant is powerful enough to handle
everything from compiling the Java source code to copying files to producing
WAR files (MSAJSP Section 4.3).
The disadvantage of ant is the overhead of learning to use
it; there is more of a learning curve with ant
than with the other techniques in this section.
Reprinted with permission from
Marty Hall. This tutorial is also available at
http://www.moreservlets.com/Using-Tomcat-4.html
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