1.3 A Quick Peek at Servlet Code

Now, this is hardly the time to delve into the depths of servlet syntax. Don't worry, you'll get plenty of that throughout the book. But it is worthwhile to take a quick look at a simple servlet, just to get a feel for the basic level of complexity.

Listing 1.1 shows a simple servlet that outputs a small HTML page to the client. Figure 1-2 shows the result.

Figure 1-2. Result of `HelloServlet` .

graphics/01fig02.jpg

The code is explained in detail in Chapter 3 (Servlet Basics), but for now, just notice four points:

It is regular Java code. There are new APIs, but no new syntax.
It has unfamiliar import statements. The servlet and JSP APIs are not part of the Java 2 Platform, Standard Edition (J2SE); they are a separate specification (and are also part of the Java 2 Platform, Enterprise EditionJ2EE).
It extends a standard class ( HttpServlet ). Servlets provide a rich infrastructure for dealing with HTTP.
It overrides the doGet method. Servlets have different methods to respond to different types of HTTP commands.

Listing 1.1 HelloServlet.java

 import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloServlet 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</TITLE></HEAD>\n" +                 "<BODY BGCOLOR=\"#FDF5E6\">\n" +                 "<H1>Hello</H1>\n" +                 "</BODY></HTML>");   } }

Figure 1-2. Result of HelloServlet .

Listing 1.1 HelloServlet.java

Figure 1-2. Result of `HelloServlet` .