Servlet APIs

In this tutorial you will learn about complete API of java servlet

Servlet API ( Application Programming Interface)

As you already know API ( Application Programming Interface ) is a collection of classes and interfaces. There are mainly two packages in servlet API

Servlet Hierarche

javax.servlet.

This package provides many classes and interfaces, which defines and describes the difference between a servlet class and a run time environment. This package provides 14 interfaces and 9 classes. They are-

Interfaces

• Servlet - This interface defines method for all servlets

• ServletConfig - This interface is used by servlet container to pass the parameter to servlet. This interface is used for individual servlet and unknown to the other servlets

• ServletContext - This interface contains a set of methods, which is used to communicate with the servlet container and other servlets servlets within an application

• ServletRequest - This interface provides a client request information to the servlet

• ServletResponse - This interface provides a servlet response information to the client, it assists the servlet to send the response information to the client.

• RequestDispatcher - This interface accepts the request from the client sends it to the other application resources.

• Filter - It performs the filter task on either request or response to the resources

• FilterChain - This view a chain of filter request for a resource.

• FilterConfig - It used by the servlet container to pass the information during initialization to the of the filter

• ServletContextListener - This interface receive a notification when a ServletContext of a web application is initialaised

• ServletRequestListener - This interface can be implemented if developer wants to notify when any  request out of the scope of web application is coming

• ServletContextAttributeListener - This interface receive a notification when a change is made in the ServletContext

• ServletRequestAttributeListener - This interface receive a notification when changes is made in request attribute.

• SingleThreadModel - This interface is deprecated after the java servlet 2.4.

Classes

• GenericServlet - This class defines a generic, protocol independent servlet.

• ServletContextAttributeEvent - This is a event class for, when the attribute of an application changes this class receives a nification.

• ServletContextEvent - This class receive a notifications when the ServletContext  of an application is changes.

• ServletInputStream - This provides a servlet input stream for reading binary data from the client.

• ServletOutputStream - This class provides an output steam for sending binary data to the client.

• ServletRequestWrapper - This class provides the implementation of ServletRequest interface, the developers can subclass this for their own specific use

• ServletResponseWrapper - This class provides the implementation of ServletResponse interface, the developers can subclass this for their own specific use

• ServletRequestAttributeEvent - This is a event class it receive a notification when any change made in the request attribute of the application

• ServletRequestEvent - This event class indicates the events of the servlet class

javax.servlet.http.

This package provides classes and interfaces which is HTTP protocol specific. There are 8 interfaces and 7 classes in this package

Interfaces

• HttpServletRequest - This interface extends the ServletRequest interface for provide http specific servlet request

• HttpServletResponse - This interface extends the ServletResponse interface for provide http specific servlet response

• HttpSession - It provides a way for identifying a user on the website

• HttpSessionActivationListener - This interface notify when when session is Activated

• HttpSessionAttributeListener - This interface can be implemented in order to get notification when attribute of the session is changed

• HttpSessionBindingListener - This interface can be implemented in order to get notification when object is bound or unbound to the session

• HttpSessionContext - This interface is deprecated in servlet 2.1 for security resion

• HttpSessionListener - When developer want to notify the session activation or de-activation, can implement this interface

Classes

• Cookie - It creates a cookie sent by a servlet to the web  browser, which browser saves and latter return for further communication

• HttpServlet - This is an abstract class, to create a Http specific servlet you need to extend this class

• HttpServletRequestWrapper -This class implements the HttpServletRequest interface, the developer can also subclass this for their specific use

• HttpServletResponseWrapper - This class implements the HttpServletResponse interface, the developer can also subclass this for their specific use

• HttpSessionBindingEvent - This is an events class, it is activated when session is bound and unbound

• HttpSessionEvent - This event class generates a notification for changes to the session within a web application

• HttpUtils - This class is deprecated in servlet 2.3 API