Servlet API
Servlet API consists of two important packages that encapsulates all the important classes and interface, namely :
- javax.servlet
- javax.servlet.http
Some Important Classes and Interfaces of javax.servlet
| INTERFACES | CLASSES |
|---|---|
| Servlet | ServletInputStream |
| ServletContext | ServletOutputStream |
| ServletConfig | ServletRequestWrapper |
| ServletRequest | ServletResponseWrapper |
| ServletResponse | ServletRequestEvent |
| ServletContextListener | ServletContextEvent |
| RequestDispatcher | ServletRequestAttributeEvent |
| SingleThreadModel | ServletContextAttributeEvent |
| Filter | ServletException |
| FilterConfig | UnavailableException |
| FilterChain | GenericServlet |
| ServletRequestListener |
Some Important Classes and Interface of javax.servlet.http
| CLASSES and INTERFACES | |
|---|---|
| HttpServlet | HttpServletRequest |
| HttpServletResponse | HttpSessionAttributeListener |
| HttpSession | HttpSessionListener |
| Cookie | HttpSessionEvent |
Servlet Interface
Servlet Interface provides five methods. Out of these five methods, three methods are Servlet life cycle methods and rest two are non life cycle methods.
GenericServlet Class
GenericServlet is an abstract class that provides implementation of most of the basic servlet methods. This is a very important class.
Methods of GenericServlet class
public void init(ServletConfig)public abstract void service(ServletRequest request,ServletResposne response)public void destroy()public ServletConfig getServletConfig()public String getServletInfo()public ServletContext getServletContext()public String getInitParameter(String name)public Enumeration getInitParameterNames()public String getServletName()public void log(String msg)public void log(String msg, Throwable t)
HttpServlet class
HttpServlet is also an abstract class. This class gives implementation of various
service() methods of Servlet interface.
To create a servlet, we should create a class that extends HttpServlet abstract class. The Servlet class that we will create, must not override
service() method. Our servlet class will override only the doGet() and/or doPost() methods.
The
service() method of HttpServlet class listens to the Http methods (GET, POST etc) from request stream and invokes doGet() or doPost() methods based on Http Method type.