Why HttpServlet class is declared as abstract? [closed]

Answer 1

HttpServlet class is declared as abstract class why because sun people dont want to create an object to HttpServlet class for this reason it is declared as abstract.

How you know that HttpServlet class have no abstarct methods

public class TestServlet extends HttpServlet{ } //compile the above program if we are able to compile then there are no abstract methods in the HttpServlet class which we need to over ride.

Answer 2

Probably, to prevent direct instantiation of HttpServlet by creating its instance.

In other words, to make sure that whenever HttpServlet is used, it is always extended by the subclass.

---

No... It can be overridden. Here is the example from Herbert Shcildt Java 2: The Complete reference

import java.io.*;

import javax.servlet.*;

public class HelloServlet extends GenericServlet

{

public void service(ServletRequest request,ServletResponse response) throws ServletException, IOException

{

response.setContentType("text/html");

PrintWriter pw = response.getWriter();

pw.println("<B>Hello!");

pw.close();

}

}

Answer 3

It's because it follows the Template Method design pattern. The doXxx() methods have all default behaviours of returning a HTTP 405 Method Not Implemented error. If those methods were all abstract, you would be forced to override them all, even though your business requirements don't need it at all. It would only result in boilerplate code and unspecified/unintuitive behaviour.

Answer 4

It is declared as a class instead of an interface to implement most of the cruft/repeatable code required for setting up a servlet. It is declared as abstract since it wouldn't make sense to instantiate a "bare bones" servlet which takes care only of the setup and doesn't contain any custom/user defined logic in it.

Answer 5

HttpServlet is an abstract class without any abstract method because the web container manufacturer restricts developer to create an object of it by declaring it abstract.

Web container should call doGet() and doPost() and it should handle all the life cycle of Servlet.

If we are allowed to create an object of HttpServlet, we are restricting container to call doGet() and doPost(), but that is the job of container itself, it should handle all the life cycle of Servlet.

So, that is why, we should not create an object of HttpServlet, so that is why it is marked abstract class without it having any abstract method.

Answer 6

all the methods of HttpServlet class are concrete even we declare this class as abstract because 1>any class can have null or more abstract method as well as concrete method . 2>always we make our servlet by extending HttpServlet.hence only derived servlet class can make object.