The Java TM Tutorial

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Trail: Servlets
Lesson: Overview of Servlets

## A Simple Servlet

> The following class completely defines servlet:

>         public class SimpleServlet extends HttpServlet
>         {
>             /**
>              * Handle the HTTP GET method by building a simple web page.
>              */
>             public void doGet (HttpServletRequest request,
>                     	   HttpServletResponse response)
>             throws ServletException, IOException
>             {
>     	    PrintWriter		out;
>     	    String		title = "Simple Servlet Output";

>     	    // set content type and other response header fields first
>                 response.setContentType("text/html");

>     	    // then write the data of the response
>     	    out = response.getWriter();

>                 out.println("<HTML><HEAD><TITLE>");
>     	    out.println(title);
>     	    out.println("</TITLE></HEAD><BODY>");
>     	    out.println("<H1>" + title + "</H1>");
>     	    out.println("<P>This is output from SimpleServlet.");
>     	    out.println("</BODY></HTML>");
>     	    out.close();
>             }
>         }

> That's it!

> The classes mentioned in the Architecture of the Servlet Package section are shown in the example in bold:

> - `SimpleServlet` extends the `HttpServlet` class, which implements the `Servlet` interface.
> - `SimpleServlet` overrides the `doGet` method in the `HttpServlet` class. The `doGet` method is called when a client makes a GET request (the default HTTP request method), and results in the simple HTML page being returned to the client.
> - Within the `doGet` method,
>   - The user's request is represented by an `HttpServletRequest` object.
>   - The response to the user is represented by an `HttpServletResponse` object.
>   - Because text data is returned to the client, the reply is sent using the `Writer` object obtained from the `HttpServletResponse` object.

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