A Tutorial on Installing and Using Tomcat for Servlet and JSP Development

More Servlets & JSP
Core Servlets & JSP

Integrating Tomcat with a regular Web server is valuable for a deployment scenario, but my goal here is to show how to use Tomcat as a development server on your desktop. Regardless of what deployment server you use, you'll want a standalone server on your desktop to use for development. (Note: Tomcat is sometimes referred to as Jakarta Tomcat since the Apache Java effort is known as "The Jakarta Project").

The examples here assume you are using Windows, but they can be easily adapted for Solaris, Linux, and other versions of Unix. I've gotten reports of successful use on MacOS X, but don't know the setup details. Except when I refer to specific Windows paths (e.g., C:\blah\blah), I use URL-style forward slashes for path separators (e.g., install_dir/webapps/ROOT). Adapt as necessary.

The information here is adapted from More Servlets and JavaServer Pages from Sun Microsystems Press. For the book table of contents, index, source code, etc., please see http://www.moreservlets.com/. For information on servlet and JSP training courses (either at public venues or on-site at your company), please see http://courses.coreservlets.com/. To report errors or omissions in this writeup or to inquire about an on-site servlet and JSP training course, please contact Marty at hall@coreservlets.com.

I give extremely detailed instructions in the following sections. If you're pretty experienced and just want a short summary, this section will probably be enough for you.

1. Install the JDK. Make sure you have JDK 1.3 or 1.4 installed and your PATH set so that both "java -version" and "javac -help" give a result.
2. Configure Tomcat.
   1. Download the software. Go to http://jakarta.apache.org/builds/jakarta-tomcat-4.0/release/ and download and unpack the zip file for the latest version.
   2. Change the port to 80. Edit install_dir/conf/server.xml and change the port attribute of the Connector element from 8080 to 80.
   3. Turn on servlet reloading. Edit install_dir/conf/server.xml and add a DefaultContext subelement to the main Service element and supply true for the reloadable attribute.
   4. Set the JAVA_HOME variable. Set it to refer to the base JDK directory, not the bin subdirectory.
   5. Change the DOS memory settings. If you get an "Out of Environment Space" error message when you start the server, right-click on install_dir/bin/startup.bat, select Properties, select Memory, and change the Initial Environment entry from Auto to at least 2816. Repeat the process for install_dir/bin/shutdown.bat.
   6. Set the CATALINA_HOME variable. Optionally, set CATALINA_HOME to refer to the top-level Tomcat installation directory.
3. Test the server.
   1. Verify that you can start the server. Double-click install_dir/bin/startup.bat and try accessing http://localhost/.
   2. Check that you can access your own HTML & JSP pages. Drop some simple HTML and JSP pages into install_dir/webapps/ROOT and access them with http://localhost/filename.
4. Set up your development environment.
   1. Create a development directory. Put it anywhere except within the Tomcat installation hierarchy.
   2. Make shortcuts to the Tomcat startup & shutdown Scripts. Put shortcuts to install_dir/bin/startup.bat and install_dir/bin/shutdown.bat in your development directory and/or on your desktop.
   3. Set your CLASSPATH. Include the current directory ("."), install_dir/common/lib/servlet.jar, and the main development directory.
   4. Bookmark the servlet & JSP javadocs. Add install_dir/webapps/tomcat-docs/servletapi/index.html to your bookmarks/favorites list.
5. Compile and test some simple servlets.
   1. Test a packageless servlet. Compile a simple servlet, put the .class file in install_dir/webapps/ROOT/WEB-INF/classes, and access it with http://localhost/servlet/ServletName.
   2. Test a servlet that uses packages. Compile the servlet, put the .class file in install_dir/webapps/ROOT/WEB-INF/classes/packageName, and access it with http://localhost/servlet/packageName.ServletName.
   3. Test a servlet that uses packages and utility classes. Follow the same procedure as the second step above. This third step verifies that the CLASSPATH includes the top level of your development directory.
6. Establish a simplified deployment method.
   1. Copy to a shortcut. Make a shortcut to install_dir/webapps/ROOT. Copy packageless .class files directly there. With packages, copy the entire directory there.
   2. Use the -d option of javac. Use -d to tell Java where the deployment directory is.
   3. Let your IDE take care of deployment. Tell your IDE where the deployment directory is and let it copy the necessary files.
   4. Use ant or a similar tool. Use the Apache make-like tool to automate copying of files.

Your first step is to download and install Java. The servlet 2.3 specification requires Java 2; I suggest JDK 1.3 or later. See the following sites for download and installation information. Once you've installed Java, confirm that everything including your PATH is configured properly by opening a DOS window and typing "java -version" and "javac -help". You should see a real result both times, not an error message about an unknown command. Or, if you use an IDE, compile and run a simple program to confirm that the IDE knows where you installed Java.

• JDK 1.3 (Windows, Linux, Solaris): http://java.sun.com/j2se/1.3/.
• JDK 1.4 (Windows, Linux, Solaris): http://java.sun.com/j2se/1.4/.
• Java 2 (Other platforms): http://java.sun.com/cgi-bin/java-ports.cgi.

Configuring Tomcat involves six steps:

1. Downloading the Jakarta Tomcat software.
2. Changing the port from 8080 to 80.
3. Telling Tomcat to reload servlets when they are modified.
4. Setting the JAVA_HOME variable.
5. Changing the DOS memory settings.
6. Setting the CATALINA_HOME variable.

1. Download the Tomcat Software

Note: from this point forward, I'll refer to that location as install_dir.

2. Change the Port to 80

To change the port, edit install_dir/conf/server.xml and change the port attribute of the Connector element from 8080 to 80, yielding the result below.

  <Connector
    className="org.apache.catalina.connector.http.HttpConnector"
    port="80" ...
    ... />

3. Turn on Servlet Reloading

To turn on servlet reloading, edit install_dir/conf/server.xml and add a DefaultContext subelement to the main Service element and supply true for the reloadable attribute. The easiest way to do this is to find the following comment:

        <!-- Define properties for each web application.  This is only needed
             if you want to set non-default properties, or have web application
             document roots in places other than the virtual host's appBase
             directory.  -->

        <DefaultContext reloadable="true"/> 

4. Set the JAVA_HOME Variable

Next, you must set the JAVA_HOME environment variable to tell Tomcat where to find Java. Failing to properly set this variable prevents Tomcat from handling JSP pages. This variable should list the base JDK installation directory, not the bin subdirectory. For example, if you are on Windows 98/Me and installed the JDK in C:\JDK1.3_01, you might put the following line in your autoexec.bat file.

  set JAVA_HOME=C:\JDK1.3_01

Rather than setting the JAVA_HOME environment variable globally in the operating system, some developers prefer to edit the startup script to set it there. If you prefer this strategy, edit install_dir/bin/catalina.bat and change the following:

  if not "%JAVA_HOME%" == "" goto gotJavaHome
  echo You must set JAVA_HOME to point at ...
  goto cleanup
  :gotJavaHome

  if not "%JAVA_HOME%" == "" goto gotJavaHome
  set JAVA_HOME=C:\JDK1.3_01
  :gotJavaHome

5. Change DOS Memory Settings

6. Set the CATALINA_HOME Variable

Testing the server involves two steps:

1. Verifying that the server can even start.
2. Checking that you can access your own HTML and JSP pages.

1. Verify That the Server Can Start

To halt the server, double click on install_dir/bin/shutdown.bat. I recommend that you make shortcuts to (not copies of) the startup and shutdown scripts and place those shortcuts on the desktop or in your main development directory. If you use an IDE, you'll have to tell it where these scripts are.

2. Try Some Simple HTML and JSP Pages

Eventually, you will almost certainly want to create and use your own Web applications (see Chapter 4 of More Servlets and JavaServer Pages), but for initial testing I recommend that you use the default Web application. Although Web applications follow a common directory structure, the exact location of the default Web application is server specific. With Tomcat 4 and the default Web application, you put HTML and JSP pages in install_dir/webapps/ROOT or install_dir/webapps/ROOT/SomePath and access them with http://localhost/filename or http://localhost/SomePath/filename. Note that Tomcat creates install_dir/webapps/ROOT when the server is first run. So, you must start the server as described above before trying to access the directory.

For your first tests, I suggest you simply take Hello.html(http://www.moreservlets.com/code/Hello.html) and Hello.jsp(http://www.moreservlets.com/code/Hello.jsp) and drop them into the appropriate locations. Right click on the links to download these two files to your system. The code for these files, as well as all the code from the book, is available online at http://www.moreservlets.com/. That Web site also contains book updates, additions, information on servlet and JSP short courses, and the full text of Core Servlets and JavaServer Pages (in PDF).

If you put the files in the top-level directory of the default Web application (i.e., in install_dir/webapps/ROOT), access them with the URLs http://localhost/Hello.html and http://localhost/Hello.jsp, respectively. If you put them in a subdirectory of install_dir/webapps/ROOT, use the URLs http://localhost/directoryName/Hello.html and http://localhost/directoryName/Hello.jsp, respectively.

If neither the HTML file nor the JSP file works (e.g., you get File Not Found--404--errors), you likely are using the wrong directory for the files. If the HTML file works but the JSP file fails, you probably have incorrectly specified the base JDK directory (e.g., with the JAVA_HOME variable).

The server startup script automatically sets the server's CLASSPATH to include the standard servlet and JSP classes and the WEB-INF/classes directory (containing compiled servlets) of each Web application. But you need similar settings, or you will be unable to compile servlets in the first place. Configuring your server for servlet development involves the following four steps:

1. Creating a development directory
2. Making shortcuts to the Tomcat startup and shutdown scripts
3. Setting your CLASSPATH
4. Bookmarking the servlet & JSP javadocs

1. Create a Development Directory

Eventually, you will organize this development directory into different Web applications (each with a common structure--see More Servlets and JavaServer Pages Chapter 4). For initial testing of your environment, however, you can just put servlets either directly in the development directory (for packageless servlets) or in a subdirectory that matches the servlet package name. Many developers simply put all their code in the server's deployment directory (within install_dir/webapps). I strongly discourage this practice and instead recommend one of the approaches described in the deployment section. Although developing in the deployment directory seems simpler at the beginning since it requires no copying of files, it significantly complicates matters in the long run. Mixing locations makes it hard to separate an operational version from a version you are testing, makes it difficult to test on multiple servers, and makes organization much more complicated. Besides, your desktop is almost certainly not the final deployment server, so you'll eventually have to develop a good system for deploying anyhow.

2. Make Shortcuts to Start and Stop the Server

For example, one way to make these shortcuts is to go to install_dir/bin, right-click on startup.bat, and select Copy. Then go to your development directory, right-click in the window, and select Paste Shortcut (not just Paste). Repeat the process for install_dir/bin/shutdown.bat. On Unix, you would use ln -s to make a symbolic link to startup.sh, tomcat.sh (needed even though you don't directly invoke this file), and shutdown.sh.

3. Set Your CLASSPATH

Now, in addition to the servlet JAR file, you also need to put your development directory in the CLASSPATH. Although this is not necessary for simple packageless servlets, once you gain experience you will almost certainly use packages. Compiling a file that is in a package and that uses another class in the same package requires the CLASSPATH to include the directory that is at the top of the package hierarchy. In this case, that's the development directory I just discussed. Forgetting this setting is perhaps the most common mistake made by beginning servlet programmers.

Finally, you should include "." (the current directory) in the CLASSPATH. Otherwise, you will only be able to compile packageless classes that are in the top-level development directory.

Here are two representative methods of setting the CLASSPATH. They assume that your development directory is C:\ServletDevel. Replace install_dir with the actual base installation location of the server. Also, be sure to use the appropriate case for the filenames. Note that these examples represent only one approach for setting the CLASSPATH. Many Java integrated development environments have a global or project-specific setting that accomplishes the same result. But these settings are totally IDE-specific and won't be discussed here.

Windows 98/Me
Put the following in your autoexec.bat. (Note that this all goes on one line with no spaces--it is broken here for readability.)

set CLASSPATH=.;
              C:\ServletDevel;
              install_dir\common\lib\servlet.jar

4. Bookmark the Servlet and JSP API Documentation

So, open install_dir/webapps/tomcat-docs/servletapi/index.html in your browser and then add it to your bookmarks (Netscape) or favorites (Internet Explorer) list. If Tomcat is running, you can also access the API with http://localhost/tomcat-docs/servletapi/index.html. However, you almost certainly will want access to the API even when the server is not running, so I recommend you open the file directly from disk and bookmark that location.

OK, so your environment is all set. At least you think it is. It would be nice to confirm that hypothesis. Verifying this involves the following three steps:

1. Testing a packageless servlet
2. Testing a servlet that uses packages
3. Testing a servlet that uses packages and utility classes

Test 1: A Servlet That Does Not Use Packages

Test 2: A Servlet That Uses Packages

Once you have placed the servlet in the proper directory, access it with the URL http://localhost/servlet/moreservlets.HelloServlet2. You should get a simple HTML page that says "Hello (2)". If this test fails, you probably either typed the URL wrong (e.g., used a slash instead of a dot after the package name) or put HelloServlet2.class in the wrong location (e.g., directly in install_dir/webapps/ROOT/WEB-INF/classes directory instead of in the moreservlets subdirectory).

Test 3: A Servlet That Uses Packages and Utilities

Since both the servlet and the utility class are in the moreservlets package, they should go in the moreservlets directory. If you get compilation errors, go back and check your CLASSPATH settings--you most likely forgot to include the top-level development directory. I've said it before, but I'll say it again: your CLASSPATH must include the top-level directory of your package hierarchy before you can compile a packaged class that makes use of another class from the same package. This requirement is not particular to servlets; it is the way packages work on the Java platform in general. Nevertheless, many servlet developers are unaware of this fact, and it is one of the (perhaps the) most common errors beginning developers encounter.

Once you compile HelloServlet3.java (which will automatically cause ServletUtilities.java to be compiled), put HelloServlet3.class and ServletUtilities.class in install_dir/webapps/ROOT/WEB-INF/classes/moreservlets. Then, access the servlet with the URL http://localhost/servlet/moreservlets.HelloServlet3. You should get a simple HTML page that says "Hello (3)".

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.

1. Copy to a shortcut or symbolic link.
2. Use the -d option of javac.
3. Let your IDE take care of deployment.
4. Use ant or a similar tool.

1. Copy to a Shortcut or Symbolic Link

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. (See Chapters 4-6 of More Servlets and JSP for details on Web applications). For instance, with Tomcat, you can easily make your own Web application by putting a copy of the install_dir/webapps/ROOT directory into your development directory and renaming it (for example, to testApp). Now, to deploy your Web application, just make a shortcut to install_dir/webapps and copy the entire Web application directory (e.g., testApp) each time by using the right mouse to drag the directory that contains your Web application onto this shortcut and selecting Copy (say Yes when asked if you want to replace existing files). Almost everything stays the same as it was without Web applications: just add the name of the directory to the URL after the hostname (e.g., replace http://locahost/blah/blah with http://locahost/testApp/blah/blah). Just note that you'll have to restart the server the very first time you deploy the directory into install_dir/webapps.

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.

2. Use the -d Option of javac

javac -d install_dir/webapps/ROOT/WEB-INF/classes
         HelloServlet2.java

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.

3. Let Your IDE Take Care of Deployment

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.

4. Use ant or a Similar Tool

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.