Servlet

Servlet

Servlet is an API provided by 'sun microsystem' to facilitate development of dynamic web applications.
The term 'servlet ' is used in two different context; in the broader context it represent an API and in the narrow context it represents an interface define using the API.

Javax.servlet  package added some packages contents classes and interfaces of servlet API, at the core of the  servlet API is an interface named ‘Servlet’ (javax.servlet.Servlet) this interface provides lifecycle methods of a servlet.

Lifecycle methods of Servlet :-

1.       init():- This method is invoke only ones just after a servlet object is created. It is used by the application developers to perform initialization

public void init(ServletConfig config) throws ServletException;

It is used by the server to provide the reference of the ServletConfig object to the servlet.

ServletConfig is an interface of servlet API implementation of it is provided by vendors.

2.       Service():- This method is invoke each time a request for the servlet is receive. It is used by the servlet  to process request and generate the html contents.

public void service(ServletRequest request, ServletResponse response)throws ServletException, IOException;

In this method references of objects of type Servletrequest and ServletResponse are provided by the server these objects act as interface between the server and the servlet that is server provides request data to  the servlet through ServletRequest object and server receives response from the servlet object through ServletResponse object.

3.       destroy():- This method is invoke only onse just before the servlet is unloaded . It is used to perform cleanup operations

public void destroy();

Non Lifecycle methods of Servlet Interface:-

1.       getServletConfig():- This method is used to obtain the reference of ‘ServletConfig’ object of a servlet.

public ServletConfig getServletConfig();

2.       getServletInfo():- This method is used to obtain the description of the servlet.

public String getServletInfo();

Note: Total five methods are available in Servlet interface – three are lifecycle and two are non lifecycle methods.