ca.on.senecac.prg556.common

Interface Control

public interface Control

Defines methods that all MVC Controls must implement.

A control is a small Java program that runs within the MVC Control framework of a J2EE Web server. Controls receive and respond to requests from Web clients, usually across HTTP, the HyperText Transfer Protocol.

This interface defines methods to initialize a control, to service requests, and to remove a control from the server. These are known as life-cycle methods and are called in the following sequence:

1. The control is constructed, then initialized with the init method.
2. Any calls from clients to the doLogic method are handled.
3. The control is taken out of service, then destroyed with the destroy method, then garbage collected and finalized.

Version:

%I% %G%

Author:

Wayne Bryan

Method Summary

Methods

Modifier and Type	Method and Description
void	destroy() Called by the MVC Control container to indicate that the control is being taken out of service.
String	doLogic(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Called by the MVC Control container to allow the control to respond to a request.
void	init() Called by the MVC Control container to indicate that the control is being placed into service.

Method Detail

init

void init()
          throws javax.servlet.ServletException

Called by the MVC Control container to indicate that the control is being placed into service.

Throws:

javax.servlet.ServletException - if an exception has occurred that interferes with the control's normal operation

doLogic

String doLogic(javax.servlet.http.HttpServletRequest request,
             javax.servlet.http.HttpServletResponse response)
               throws javax.servlet.ServletException,
                      IOException

Called by the MVC Control container to allow the control to respond to a request.

This method is only called after the control's init() method has completed successfully.

Controls typically run inside multithreaded servlet containers that can handle multiple requests concurrently. Developers must be aware to synchronize access to any shared resources such as files, network connections, and as well as the control's class and instance variables.

The method returns a String to indicate how to proceed after the method completes. A null value means continue along the filter chain to the next element. A response of "R:resource-url" indicates that a client-side redirection to the resource URL should be performed. A response of "D:resource-url" indicates that a server-side request dispatcher forward to the resource URL should be performed. For any other return value the request is not passed to the next element in the filter chain.

Parameters:

request - the HttpServletRequest object that contains the client's request

response - the HttpServletResponse object that contains the control's response

Returns:

a String indicating how to proceed after the method completes.

Throws:

javax.servlet.ServletException - if an exception has occurred that interferes with the control's normal operation

IOException - if an input or output exception occurs

See Also:

ControlFilter

destroy

void destroy()

Called by the MVC Control container to indicate that the control is being taken out of service.