JSF - Answers to Apache Struts

Java Server Faces is a component oriented and event driven framework for web applications. It is extensible, standard specification. This component driven model have given hope of role playing in web appliation development.

• Page Author can independently design a web page with easy to use tools backed by extensive tag library. 
• Application developers integrates UI design with event, valiation, convertor and objects. 
• Component Writer can write new components in extensible and customizable nature. 
  
• Architect can independently define navigation, ensure scalability of applicability and configure bean obj registration. 
• Tool Vendors can independently develop tools to make design of web a easy experience with intuitive drag-n-drop features

Trade-offs: 
JSP/Servlet: Lack of

• UI component
  

Struts: Lack of

• UI component model
  
• Event model 
• State Management 
• Support for multiple render 
• Standard 
  

Technology Orientation: 

• JSF - View / Separate controller
  
• Servlet - View/Controller combined   
  
• Struts - Controller 

But JSF and Struts can coexist. It will be suitable for application which already has struts impl and take advantage of UIComponent of JSF. 

 Building Blocks

• Component 
• Event listener
  
• Validator 
  
• Back-end data integration
  

API Stack

• JSF Tag and API
  
• JSP 1.2
  
• Servlet 2.3
  

Life-cycle of JSF:  

1. Restore View Phase

• FacesContext - Build view of JSF/wires event handlers and validator. 
• New Req - Create empty view
  
• Middle Req - Restores the view state from client/server
  

2. Apply Request Value Phase 

• decode Method - 
• Extracts values from Req parameters for all UI Component 
• Type conversion to all component
  

3. Process Validation Phase 

• Validates all extracted values to all components 
• Error - Queue it on FacesContext and advance the lifecycle to Render Response Phase. 

4. Update Model Value Phase 

• Updates/Assign server-side object with corresponding component's local value 
• Type conversion from component to model properties
  

5. Invoke Application Phase 

• Invokes any application-level events
• Invoke ActionListener Impl (success action) 
• Pass outcome to NavigationHandler (default)
  
• Navigation Rule (config file) - Match outcome to response view 
• JSF - Set response view to page
  

6. Render Response Phase 

• encode Method: 
• Renders components from component tree of FacesContext 
• Create appropriate markup for component tree 
• Save the state of response
  

Info About JSF:

• UI Component Model 
• Rendering Model, Event and listerner model, conversion model and validation model .
• Configuration File: 
• faces-config.xml 
• Types of Event: 
• ActionEvent 
• ValueChangeEvent 
• PhaseEvent
• Types of localization 
• Static data
  
• Dynamic data
  
• Messages
• Steps for Static localization 
• Create ResourceBundle
• Ref bundle from pages 
• Ref the localized messages within bundle 
• Important Top Classes  
• For view: Parent is UIView
• For component: UIComponent

JSF Component:

• Standard Component:
• UIForm - represents a user input form that is a container of other components.
• UICommand - represents UI components like buttons, hyperlinks and menu items.
• UIInput - represents UI components like text input fields, numeric input fields.

• Custom Component:
• User/Developer designed component on top of standard components as well as other custom component.
• Great feature of JSP is power to use third party components seamlessly. How to create custom component?
• Either implement UIComponent interface or extend UIComponentBase class to bring default behavoiur of component

Type of Tag Library:

• JSF Core 
• <%@ taglib uri=”http://java.sun.com/jsf/core “ prefix=”f” %>
  
• JSF Html
• <%@ taglib uri=”http://java.sun.com/jsf/html “ prefix=”h” %>

References: 

• http://www.roseindia.net/jsf/