3.4 Servlet Packaging

In a production environment, multiple programmers can be developing servlets for the same server. So, placing all the servlets in the same directory results in a massive, hard-to-manage collection of classes and risks name conflicts when two developers inadvertently choose the same name for a servlet or a utility class. Now, Web applications (see Section 2.11) help with this problem by dividing things up into separate directories, each with its own set of servlets, utility classes, JSP pages, and HTML files. However, since even a single Web application can be large, you still need the standard Java solution for avoiding name conflicts: packages. Besides, as you will see later, custom classes used by JSP pages should always be in packages. You might as well get in the habit early.

When you put your servlets in packages, you need to perform the following two additional steps.

  1. Place the files in a subdirectory that matches the intended package name. For example, we'll use the coreservlets package for most of the rest of the servlets in this book. So, the class files need to go in a subdirectory called coreservlets . Remember that case matters for both package names and directory names , regardless of what operating system you are using.

  2. Insert a package statement in the class file. For instance, for a class to be in a package called somePackage , the class should be in the somePackage directory and the first non-comment line of the file should read

     
     package somePackage; 

    For example, Listing 3.4 presents a variation of the HelloServlet class that is in the coreservlets package and thus the coreservlets directory. As discussed in Section 2.8 (Test Your Setup), the class file should be placed in install_dir /webapps/ROOT/WEB-INF/classes/coreservlets for Tomcat, install_dir /servers/default/default-ear/default-war/WEB-INF/classes/coreservlets for JRun, and install_dir /doc/WEB-INF/classes/coreservlets for Resin. Other servers have similar installation locations.

Figure 3-4 shows the servlet accessed by means of the default URL.

Listing 3.4 coreservlets/HelloServlet2.java
  package coreservlets;  import java.io.*; import javax.servlet.*; import javax.servlet.http.*; /** Simple servlet for testing the use of packages. */ public class HelloServlet2 extends HttpServlet {   public void doGet(HttpServletRequest request,                     HttpServletResponse response)       throws ServletException, IOException {     response.setContentType("text/html");     PrintWriter out = response.getWriter();     String docType =       "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +       "Transitional//EN\">\n";     out.println(docType +                 "<HTML>\n" +                 "<HEAD><TITLE>Hello (2)</TITLE></HEAD>\n" +                 "<BODY BGCOLOR=\"#FDF5E6\">\n" +                 "<H1>Hello (2)</H1>\n" +                 "</BODY></HTML>");   } } 
Figure 3-4. Result of http://localhost/servlet/coreservlets.HelloServlet2 .

graphics/03fig04.jpg



Core Servlets and JavaServer Pages (Vol. 1.Core Technologies)
Core Servlets and Javaserver Pages: Core Technologies, Vol. 1 (2nd Edition)
ISBN: 0130092290
EAN: 2147483647
Year: 2002
Pages: 194

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