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The Container initializes a servlet by loading the class, invoking the servlet’s no-arg constructor, and calling the servlet’s init() method.
The init() method (which the developer can override) is called only once in a servlet’s life, and always before the servlet can service any client requests.
The init() method gives the servlet access to the ServletConfig and ServletContext objects, which the servlet needs to get information about the servlet configuration and the web app.
The Container ends a servlet’s life by calling its destroy() method.
Most of a servlet’s life is spent running a service() method for a client request.
Every request to a servlet runs in a separate thread! There is only one instance of any particular servlet class.
Your servlet will almost always extend javax.servlet.http. HttpServlet, from which it inherits an implementation of the service() method that takes an HttpServletRequest and an HttpServletResponse.
HttpServlet extends javax.servlet.GenericServlet—an abstract class that implements most of the basic servlet methods.
GenericServlet implements the Servlet interface.
Servlet classes (except those related to JSPs) are in one of two packages: javax.servlet or javax.servlet.http.
You can override the init() method, and you must override at least one service method (doGet(), doPost(), etc.).