Java Servlet Example
Jakob Jenkov |
A Java Servlet is just an ordinary Java class which implements the interface
javax.servlet.Servlet;
The easiest way to implement this interface is to extend either the class
GenericServlet or HttpServlet.
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;
public class SimpleServlet extends GenericServlet {
public void service(ServletRequest request, ServletResponse response)
throws ServletException, IOException {
// do something in here
}
}
When an HTTP request arrives at the web server, targeted for your Servlet, the web server
calls your Servlet's service() method.
The service() method then reads the request, and generates a response which
is sent back to the client (e.g. a browser).
Here is an example service() implementation:
public void service(ServletRequest request, ServletResponse response)
throws ServletException, IOException {
String yesOrNoParam = request.getParameter("param");
if("yes".equals(yesOrNoParam) ){
response.getWriter().write(
"<html><body>You said yes!</body></html>");
}
if("no".equals(yesOrNoParam) ){
response.getWriter().write(
"<html><body>You said no!</body></html>");
}
}
This service() method first reads the request parameter "param". Then
it checks if the param is equal to the text "yes" or "no", and writes an HTML response
back to the browser.
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Jakob Jenkov | |
