November 1998
Intermediate to advanced
526 pages
14h 38m
English
Content preview from Java Servlet ProgrammingBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Page Generation
The most basic type of HTTP servlet generates a full HTML page. Such a servlet has access to the same information usually sent to a CGI script, plus a bit more. A servlet that generates an HTML page can be used for all the tasks where CGI is used currently, such as for processing HTML forms, producing reports from a database, taking orders, checking identities, and so forth.
Writing Hello World
Example 2.1 shows an HTTP servlet that generates a complete HTML page. To keep things as simple as possible, this servlet just says " Hello World” every time it is accessed via a web browser.[3]
Example 2-1. A servlet that prints “Hello World”
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("<HTML>");
out.println("<HEAD><TITLE>Hello World</TITLE></HEAD>");
out.println("<BODY>");
out.println("<BIG>Hello World</BIG>");
out.println("</BODY></HTML>");
}
}This servlet extends the HttpServlet class and
overrides the doGet()
method inherited from it. Each time the web server receives a GET
request for this servlet, the server invokes this
doGet() method, passing it an
HttpServletRequest object and an
HttpServletResponse object.
The HttpServletRequest represents the client’s request. This object gives a servlet access to information ...
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