Servlet interface provides common behaviour to all the servlets.
Servlet interface needs to be implemented for creating any servlet (either directly or indirectly). It provides 3 life cycle methods that are used to initialize the servlet, to service the requests, and to destroy the servlet and 2 non-life cycle methods.
Servlet Interface Method
There are 5 methods in Servlet interface. The init, service and destroy are the life cycle methods of servlet. These are invoked by the web container.
1. void destroy(): This method is called by Servlet container at the end of servlet life cycle. Unlike service() method that gets called multiple times during life cycle, this method is called only once by Servlet container during the complete life cycle. Once destroy() method is called the servlet container does not call the service() method for that servlet.
2. void
init(ServletConfig config): When Servlet container starts
up (that happens when the web server starts up) it loads all the servlets and
instantiates them. After this init() method gets called for each instantiated
servlet, this method initializes the servlet.
3. void
service(ServletRequest req, ServletResponse res): This
is the only method that is called multiple times during servlet life cycle.
This methods serves the client request, it is called every time the server
receives a request.
4. ServletConfig
getServletConfig(): Returns a ServletConfig object, which
contains initialization and startup parameters for this servlet.
5. java.lang.String
getServletInfo(): Returns information about the servlet, such as author,
version, and copyright.
Servlet Example by implementing Servlet interface
Let's see the simple example of servlet by implementing the servlet interface.
File : Dashzin.java
import java.io.*;
import javax.servlet.*;
public class Dashzin implements Servlet{
ServletConfig config=null;
public void init(ServletConfig config){
this.config=config;
System.out.println("servlet is initialized");
}
public void service(ServletRequest req,ServletResponse res)
throws IOException,ServletException{
res.setContentType("text/html");
PrintWriter out=res.getWriter();
out.print("<html><body>");
out.print("<b>hello simple servlet
using servlet interface</b>");
out.print("</body></html>");
}
public void destroy(){
System.out.println("servlet is destroyed");
}
public ServletConfig getServletConfig(){
return config;
}
public String getServletInfo(){
return "Welcome to Dashzin Servlet Blog";
}
}
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