Part 3: First Servlets
4. Simple HTML-Building Utilities
It is a bit cumbersome to generate HTML with println statements.
The real solution is to use Java Server Pages (JSP), which is discussed later in this tutorial.
However, for standard servlets, there are two parts of the Web page (DOCTYPE and HEAD) that are unlikely to change and thus could benefit from being incorporated into a simple utility file.
The DOCTYPE line is technically required by the HTML spec, and although most major browsers ignore it, it is very useful when sending pages to formal HTML validators.
These validators compare the HTML syntax of pages against the formal HTML specification, and use the DOCTYPE line to determine which version of HTML to check against.
Their use is very highly recommended both for static HTML pages and for pages generated via servlets, so the use of DOCTYPE is well worth the effort, especially if it can be easily incorporated into a servlet utilities class.
In many Web pages, the HEAD line contains nothing but the TITLE, although advanced developers may want to include META tags and style sheets.
But for the simple case, I'll create a method that takes a title as input and returns the DOCTYPE, HEAD, and TITLE entries as output.
Here's the code:
4.1 ServletUtilities.java
(Download source code)
package hall;
public class ServletUtilities {
public static final String DOCTYPE =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional//EN\">";
public static String headWithTitle(String title) {
return(DOCTYPE + "\n" +
"<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n");
}
// Other utilities will be shown later...
}
4.2 HelloWWW2.java
(Download source code)
Here's a rewrite of the HelloWWW class that uses this.
package hall;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWWW2 extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println(ServletUtilities.headWithTitle("Hello WWW") +
"<BODY>\n" +
"<H1>Hello WWW</H1>\n" +
"</BODY></HTML>");
}
}
This tutorial is now available as a book: Core Servlets and JavaServer Pages by Marty Hall, published by Sun Microsystems Press.
Read all about it at CoreServlets.com
Server-Side Web Applications using Java Servlets versions 2.1/2.2 and JavaServer Pages (JSP) version 1.0: A Tutorial
© 1999-2000 Marty Hall.
All source code freely available for unrestricted use.
Created for work in the Research and Technology Development Center of the Johns Hopkins University Applied Physics Lab, for courses in the Johns Hopkins Part-Time MS Program in Computer Science, and for various industry seminars and on-site Java short courses.
Please note that this is a first draft of the tutorial, so please send corrections, comments, and suggestions to me at hall@apl.jhu.edu.
Reprinted with permission from the author. Click here to visit the original version
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