GenericServlet class

GenericServlet is a abstract class which is defined in the Servlet API. GenericServlet class implements Servlet, ServletConfig and Serializable interfaces, it provides implementation for all the methods of the Servlet Interface except the service() method.

Method of GenericServlet class

  • public void init (ServletConfig) : This method is used to initialize the servlet. It indicates Servlet instance in being placed into the service.
  • public abstract void service (ServletRequest request, ServletResponse response) :This method process the request and provides the response back. This method will be called for every request from the web container.
  • public void destroy (): This method indicates the end of the servlet lifecycle. This method will be called only once
  • public ServletConfig getServletConfig (): This method returns back the ServletConfig object. It is used to get configuration information from web.xml file.
  • public ServletContext getServletContext (): It returns ServletContext object reference. It is used to get configuration information from web.xml file.
  • public String getInitParameter (String name): This method returns the Servlet initialization parameter for the given name, if the name is not preset it will return null.
  •  public Enumeration String getInitParameternames (): It returns names of all Servlet initialization parameters defined in web.xml file.
  • public String getServletInfo (): Returns information about servlet such as writer, version etc.
  • public String getServletName (): It returns the Servlet instance name defined in web.xml
  • public void log (String msg): Writes the given message in the servlet log file.
  • public void log (String msg, Throwable t): It writes log message and stack trace for a given Throwable exception to the servlet log file.

GenericServletExample.java

Lets see the below Servlet Example which inherits the GenericServlet class

import java.io.*;
import javax.servlet.*;

public class GenericServletExample extends GenericServlet
{
     public void service(ServletRequest req,ServletResponse res)
     throws IOException,ServletException
     {
          res.setContentType("text/html");
          PrintWriter out=res.getWriter();
          out.print("<html>");
          out.print("<body>");
          out.print("<h2>Generic Servlet Example!!!</h2>");
          out.print("</body>");
          out.print("</html>");
     }
}

 

web.xml

The deployment descriptor will be in XML format and called as web.xml, which sould be placed in the WEB-INF directory of the Servlet application.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
     <display-name>GenericServletExample</display-name>
     <servlet>
         <servlet-name>GenericServletExample</servlet-name>
         <servlet-class>com.javainterviewpoint.GenericServletExample</servlet-class>
     </servlet>
     <servlet-mapping>
         <servlet-name>GenericServletExample</servlet-name>
         <url-pattern>/GenericServlet</url-pattern>
     </servlet-mapping>
</web-app>

Output

To run our GenericServletExample application hit on the below url

http://localhost:8080/ServletTutorial/GenericServlet

We will get the below output displayed in the browser

Generic Servlet Example!!!

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