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GenericServlet class in java

GenericServlet class:

GenericServlet class implements the Servlet and ServletConfig interfaces. GenericServlet is protocol-independent. It not provides the implementation of service method.

public abstract class GenericServlet implements Servlet, ServletConfig

GenericServlet class is in javax.servlet package (javax.servlet.GenericServlet).

Methods of GenericServlet class:

1. init(ServletConfig config): It is used to initialize the servlet. This method is called only once by the web container when it loads the servlet.

Syntax: public void init(ServletConfig config)throws ServletException

2. service(ServletRequest request,ServletResponse response): It is used to respond to a request. It is called for every new request by web container.

Syntax: public abstract void service(ServletRequest req,ServletResponse res)throws ServletException, IOException

3. destroy(): It is used to destroy the servlet. This method is called only once by the web container when all threads of the servlet have exited or in a timeout case.

Syntax: public void destroy()

4. getServletConfig(): It returns a servlet config object. This config object is passed in init method.  Servlet config object contains initialization parameters and startup configuration for this servlet.

Syntax: public ServletConfig getServletConfig()

5. getServletInfo(): It returns a string of information about servlet’s author, version, and copyright etc.

Syntax: public String getServletInfo()

6. Init(): It is a convenience method which can be overridden so that there is no need to call super.init(config).

Syntax: public void init() throws ServletException

7. getServletContext():It returns the ServletContext object in which this servlet is running.

Syntax: public ServletContext getServletContext()

8. getInitParameter(String name): It returns the value for given parameter name. It returns null if parameter not exist.

Syntax: public String getInitParameter(String name)

9. getInitParameterNames(): It returns the names of the servlet’s initialization parameters defined in web.xml file.

Syntax: public Enumeration getInitParameterNames()

10. getServletName(): It returns the name of this servlet object.

Syntax: public String getServletName()

11. log(String msg): This method writes the specified message to the servlet log file.

Syntax: public void log(String msg)

12. log(String msg,Throwable t): This method writes an explanatory message and a stack trace for a given exception to the servlet log file.

Syntax: public void log(String msg,Throwable t).

Servlet “Hello World” example by extending GenericServlet class.

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
 * This servlet program is used to print "Hello World" on 
 * client browser using GenericServlet class.
 * @author codesjava
public class HelloWorld extends GenericServlet {
    private static final long serialVersionUID = 1L;
    //no-argument constructor.
    public HelloWorld() {
    public void service(ServletRequest request, ServletResponse response)
			throws ServletException, IOException {
	PrintWriter out = response.getWriter();
        out.println("<h1>Hello World example using" +
	    		" GenericServlet class.</h1>");


<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" 


servlet example 2
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