Essentially, the camera itself is just a light-tight box with a shutter! Photography is all about capturing light on a photographic emulsion or electronic sensor. And as such the lens and film or sensor, are the most important components affecting image quality.

Lens is to change the angle of view in the image, So they can have a major impact on the resulting photograph. In this beginners guide I intend to describe the technical terms and different properties of lenses.

To be a servlet, a class should extend HttpServlet and override doGet or doPost, depending on whether the data is being sent by GET or by POST. If you want the same servlet to handle both GET and POST and to take the same ction for each, you can simply have doGet call doPost, or vice versa.

Both of these methods take two arguments: an HttpServletRequest and an HttpServletResponse. The HttpServletRequest has methods by which you can find out about incoming information such as form data, HTTP request headers, and the client's hostname. The HttpServletResponse lets you specify outgoing information such as HTTP status codes (200, 404, etc.), response headers (Content-Type, Set-Cookie, etc.), and, most importantly, lets you obtain a PrintWriter used to send the document content back to the client. For simple servlets, most of the effort is spent in println statements that generate the desired page. Form data, HTTP request headers, HTTP responses, and cookies will all be discussed in detail in the following chapters.