How JSF Fits For Web Applications?

JSF best suits in to the java web development environment because of reasons described  below : JSF has many  advantages over other existing frameworks that makes it a better choice for web application development. Some of the reasons are below:

Easy creation of UI:
It makes easier to create complex UI for an applicaton using jsf tags.Its APIs are layered directly on  top of servlet APIs that enables us to use  presentation technology other than JSP,creating your own custom components and rendering output for various client devices.

Capacity to handle complexities of UI management: 
It handles cleanly the complexities of UI management like input validation, component-state management, page navigation, and event handling.

Clean separation between presentation and logic:
One of the greatest advantage of jsf is to clearly separate behaviour and presentation in an application. JSF is based on the Model View Controller (MVC) architecture.

Shorter development cycle:
This  separation between logic and presentation enables a wide range of users( from web-page designers to component developers). It allows members of team to focus on their own work only , resulting in division of labour and shorter development cycle.

Standard Java framework:
JSF is a Java standard which is being developed through Java Community Process (JCP). Several prominent tool vendors are members of the group and are committed  to provide easy to use, visual, and productive develop environments for JavaServer Faces.             

An extensible architecture:   
JSF architecture has been designed to be extensible.Extensible means additional functionality can be given on the top of JSF core i.e. we can customize the functionality. JSF UI components are customizable and reusable elements. You can extend standard components and create your own complex  components like stylish calendar, menu bar etc.

Support for multiple client devices:
Component developers can extend the component classes to generate their own component tag libraries to support specific client. JSF flexible and extensible architecture allows developers to do so.

Flexible rendering model:
Renderer separates the functionality and view of the component. So we can create multiple renderers and give them different functionality to get different appearance of the same component for the same client or different .

International language support:
 Java has excellent support for internationalization . It allows you to localize messages  with user specific locale. A locale is a combination of a country, a language, and a variant code. JavaServer Faces adopts this property and let you specify which locale your application supports. So you can display you messages in different languages.

Robust tool support:
There are several standard tool vendors like Sun Java Studio Creator who provide robust tools that take advantages of JSF to create server side UI  easily.