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To handle HTTP requests in a servlet, extend the
HttpServlet
class and override the servlet methods that handle the HTTP requests that your servlet supports. This lesson illustrates the handling of GET and POST requests. The methods that handle these requests aredoGet
anddoPost
.
Handling GET requests involves overriding the doGet
method.
The following example shows the BookDetailServlet doing this. The methods
discussed in the Requests and Responses section are
shown in bold.
public class BookDetailServlet extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ... // set content-type header before accessing the Writer response.setContentType("text/html"); PrintWriter out = response.getWriter(); // then write the response out.println("<html>" + "<head><title>Book Description</title></head>" + ...); //Get the identifier of the book to display String bookId = request.getParameter("bookId"); if (bookId != null) { // and the information about the book and print it ... } out.println("</body></html>"); out.close(); } ... }
The servlet extends the HttpServlet
class and overrides the
doGet
method.
Within the doGet
method, the getParameter
method gets the servlet's expected argument.
To respond to the client, the example doGet
method uses a
Writer
from the HttpServletResponse
object to
return text data to the client. Before accessing the writer, the example
sets the content-type header. At the end of the doGet
method,
after the response has been sent, the Writer
is closed.
Handling POST requests involves overriding the doPost
method. The following example shows the ReceiptServlet doing this. Again,
the methods discussed in the Requests and
Responses section are shown in bold.
public class ReceiptServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ... // set content type header before accessing the Writer response.setContentType("text/html"); PrintWriter out = response.getWriter(); // then write the response out.println("<html>" + "<head><title> Receipt </title>" + ...); out.println("<h3>Thank you for purchasing your books from us " + request.getParameter("cardname") + ...); out.close(); } ... }
The servlet extends the HttpServlet
class and overrides the
doPost
method.
Within the doPost
method, the getParameter
method gets the servlet's expected argument.
To respond to the client, the example doPost
method uses a
Writer
from the HttpServletResponse
object to
return text data to the client. Before accessing the writer the example
sets the content-type header. At the end of the doPost
method, after the response has been set, the Writer
is closed.
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