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(The same is true if you put this address into a simple hyperlink when creating a web page.)
If you want to manually enter an address into the address field and cause the doPost method to be called, you must find some other way to do it.
Arguments
Each of the methods requires two arguments. The first, a reference to an HttpServletRequest object, encapsulates the data from the client. The second, a reference to an HttpServletResponse object encapsulates the response to the client.
The HttpServletRequest object provides a large number of methods that the servlet can use to obtain information about the request.
Similarly, the HttpServletResponse object provides a large number of methods that the servlet can use to return data to the client.
The init and destroy methods
You may also find that you need to override the init and destroy methods in your servlet. Recall that each of these methods is called only once. The init method is called when the server loads the servlet class. The destroy method is called when the server removes the servlet class.
Overriding the init method
The servlet should use the init method to prepare the resources it manages and to make the servlet ready to handle client requests. It can do this without regard for multi-threading issues because it is guaranteed that there is only a single thread running during initialization. If the init method is unable to run to a successful completion, it should throw an UnavailableException object.
The init method receives a ServletConfig object as a parameter. For reasons that I won't bother to discuss here, the overridden init method should call super.init and pass this configuration object as a parameter. If you are curious as to the reasons, you can look it up in the documentation.
Overriding the destroy method
Overriding the destroy method is more problematic, particularly if it is necessary to deal with resources that may be shared by service threads that are still running when the server decides to remove the servlet and call its destroy method. I'm going to punt on this one, and suggest that if you find yourself in this situation, you should find a good bookwith an example similar to your situation and use that example for guidance.
The getServletInfo method
Some applications may want to display information about a servlet, such as a short description of the purpose of the servlet, its author, and perhaps its version number. The Servlet API provides a method named getServletInfo to return this kind of information about the servlet. By default, this method returns null. You can override this method to return a String containing information about your servlet.
The next module in the series will take on forms and databases.
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
| Listing 6 - Servlet01.java. |
|---|
/*File Servlet01.java, Copyright 1999, R.G.Baldwin
The purpose of this program is to illustrate a verysimple servlet.
The servlet produces the following text in the browserwindow in large red letters.
Hello Big Red World**********************************************************/
import java.io.*;import javax.servlet.*;
import javax.servlet.http.*;public class Servlet01 extends HttpServlet{
public void doGet(HttpServletRequest req,
HttpServletResponse res)throws ServletException, IOException{
//Establish the type of outputres.setContentType("text/html");//Get an output stream
PrintWriter out = res.getWriter();//Construct an html page to return to the clientout.println("<html>");
out.println("<head><title>Servlet01</title></head>");
out.println("<body>");out.println("<h1 align=\"center\">"
+"<font color=\"#FF0000\">");
out.println("Hello Big Red World");out.println("</font></h1>");
out.println("</body></html>");
}//end doGet()}//end class Servlet01 |
-end-
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