Servlet methods

1
Servlet methods

• Some methods inherited from the HttpServlet
  class
• init ? initialization code here
• doGet ? handle a get request here
• doPost ? handle a post request here
• destroy ? cleanup code here
• These methods can be overridden by you, the
  programmer
• These methods are called automatically
• ? Remember applets ?

2
Servlet doGet method

• Called by the server to allow a servlet to handle
  a GET request.
• When overriding this method,
• read the request data,
• get the response's writer or output stream
  object,
• write the response headers,
• write the response data.
• When using a PrintWriter object to return the
  response, set the content type before accessing
  the PrintWriter object.

3
Servlet doGet method

• The method header is
• public void doGet( HttpServletRequest request,
• HttpServletResponse response)
• throws IOException,
• 
  ServletException
• ? We have access to the HttpServletRequest and
  HttpServletResponse parameters (remember the 2
  implicit objects request and response in JSPs)

4
Perl, PHP, JSPs, Servlets
5
Servlet doGet method

• // Inside doGet
• // set the content type
• response.setContentType( text/html )
• / get a PrintWriter object so that we can output
  content /
• PrintWriter out response.getWriter( )
• // Output contents
• out.println( lthtmlgt .. lt/htmlgt )

6
First Servlet

• package helloWorld
• import javax.servlet.
• import javax.servlet.http.
• import java.io.

7
First Servlet

• public class HWServlet extends HttpServlet
• public void doGet( HttpServletRequest request,
• HttpServletResponse response) throws
  IOException, ServletException
• response.setContentType( text/html )
• try
• PrintWriter out response.getWriter( )
• out.println( lthtmlgtltbodygtHello
  Worldlt/bodygtlt/htmlgt )
• catch( IOException ioe )

8
First Servlet

• Place HelloServlet.class in webapps directory in
  a package
• Map it to helloFromHF (or something else) in
  web.xml
• url is http//leda.capitol-college.edu8180/hfran
  ceschi/helloFromHF

9
Servlet Mapping

• Inside web.xml
• ltservletgt
• ltservlet-namegtHelloServletlt/servlet-namegt
• ltservlet-classgtmypackage.HelloServletlt/ser
  vlet-classgt
• lt/servletgt
• ltservlet-mappinggt
• ltservlet-namegtHelloServletlt/servlet-namegt
• lturl-patterngt/helloFromHFlt/url-patterngt
• lt/servlet-mappinggt