The HttpServlet class extends the GenericServlet class and implements Serializable interface. It provides http specific methods such as doGet, doPost, doHead, doTrace etc.
Hierarchy of Http
Servlet
Hierarchy of Http
Servlet
java.lang.Object
|_extended by javax.servlet.GenericServlet
|_extended by 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 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 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 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 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 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 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 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 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 time is unknown.
Syntax: protected long getLastModified(HttpServletRequest req)
Example of HttpServlet class
Create a dynamic web project and then write the code HttpServlet class.
index.html
index<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>HttpServlet Demo</title>
</head>
<body>
<a href="welcome">Click to call Servlet</a>
</body>
</html>
ExampleHttpServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
// Creating Http Servlet by Extending HttpServlet class
public class ExampleHttpServlet extends HttpServlet
{
private String mymsg;
public void init() throws ServletException
{
mymsg = "Http Servlet Demo";
}
public void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException
{
// Setting up the content type of web page
response.setContentType("text/html");
// Writing the message on the web page
PrintWriter out = response.getWriter();
out.println("<h1>" + mymsg + "</h1>");
out.println("<p>" + "Hello Guys!" + "</p>");
}
public void destroy()
{
// Leaving empty. Use this if you want to perform
//something at the end of Servlet life cycle.
}
}
Web.xml
<web-app>
<display-name>Dashzin Servlet</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>MyHttpServlet</servlet-name>
<servlet-class>ExampleHttpServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyHttpServlet</servlet-name>
<url-pattern>/welcome</url-pattern>
</servlet-mapping>
</web-app>
Output
for output and more clarity on the above example just copy and past in your eclipse and run it and check your output. After that try to write the other example so that you will get more confident on HttpServlet Class.
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