updated Basic-Servlets-Examples readme commit

Author: SuneetPatil

Basic-Servlets-Examples/README.md

@@ -1,10 +1,36 @@
+## The servlet can be created by three ways:
+* By implementing Servlet interface,
+* By inheriting GenericServlet class, (or)
+* By inheriting HttpServlet class
 
-# Servlet Life Cycle
+### GenericServlet
+* Implements  Servlet, ServletConfig andSerializable interface. 
+* It provides the implementaion of all the methods of these interfaces except the service method.
+* GenericServlet class can handle any type of request so it is protocol-independent.
 
-![Servlet Life Cycle](https://github.com/SuneetPatil/Java-Servlets/blob/master/Images/ServletLifeCycle.png)
+### HttpServlet
+* class extends the GenericServlet class and implements Serializable interface. 
+* It provides http specific methods such as doGet, doPost, doHead, doTrace etc
 
-* If an instance of the servlet does not exist, the Web container loads the class. 
-* Creates an instance of the servlet class. 
-* Initializes the servlet instance by calling the init method.
-* Invokes the service method, passing a request and response object, For Http Servlet, Service method invokes doGet, doPost, etc. methods as appropriate,  Override only doGet or doPost etc. method as needed.
-* Finalize the request by calling Destroy method.
+## Package and Deployment
+ <p align="center"> 
+    <img src="https://github.com/SuneetPatil/Java-Servlets/blob/master/Images/PackageandDeployment.png" alt="Package and Deployment">
+ </p>
+
+### Deployment Descriptor :
+* web.xml is the deployment descriptor for web applications.
+* Every web application module must have a single web.xml file in the folder root/WEB-INF
+
+```
+<web-app>
+  <servlet>
+    <servlet-name>GenericServlet</servlet-name>
+    <servlet-class>com.suneet.GenericServletExample</servlet-class>
+  </servlet>
+  <servlet-mapping>
+    <servlet-name>GenericServlet</servlet-name>
+    <url-pattern>/exampleservlet</url-pattern>
+  </servlet-mapping>
+</web-app>
+
+```