HttpServlet class:
HttpServlet class extends the GenericServlet. It is protocol-dependent.
public abstract class HttpServlet extends GenericServlet
HttpServlet class is in javax.servlet.http package (javax.servlet.http.HttpServlet).
Methods of HttpServlet class:
1. service(ServletRequest req,ServletResponse res): Dispatches the requests to the protected service method. It converts the request and response object into HTTP type before dispatching the request.
Syntax:
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException
2. service(HttpServletRequest req, HttpServletResponse res): Receives HTTP requests from the public service method and dispatches the request to the doXXX methods defined in this class.
Syntax:
protected void service(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
3. doGet(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling GET requests.
Syntax:
protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
4. doPost(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling POST requests.
Syntax:
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
5. doHead(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling HEAD requests.
Syntax:
protected void doHead(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
6. doOptions(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling OPTIONS requests.
Syntax:
protected void doOptions(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
7. doPut(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling PUT requests.
Syntax:
protected void doPut(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
8. doTrace(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling TRACE requests.
Syntax:
protected void doTrace(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
9. doDelete(HttpServletRequest req, HttpServletResponse res): This method is called by the web container for handling DELETE requests.
Syntax:
protected void doDelete(HttpServletRequest req, HttpServletResponse res) throws ServletException,IOException
10. getLastModified(HttpServletRequest req): It returns the time the HttpServletRequest object was last modified since midnight January 1, 1970 GMT. It returns a negative number if the time is unknown.
Syntax:
protected long getLastModified(HttpServletRequest req)
Servlet “Hello World” example by extending the HttpServlet class.
HelloWorld.java
import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelloWorld extends HttpServlet { private static final long serialVersionUID = 1L; //no-argument constructor. public HelloWorld() { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("Hello World using HttpServlet class."); out.close(); } }
web.xml
<!--?xml version="1.0" encoding="UTF-8"?--> <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <servlet> <servlet-name>HelloWorld</servlet-name> <servlet-class> com.w3schools.business.HelloWorld </servlet-class> </servlet> <servlet-mapping> <servlet-name>HelloWorld</servlet-name> <url-pattern>/HelloWorld</url-pattern> </servlet-mapping> </web-app>