Post 1: JSF: Introduction to JSF

Post 1: JSF: Introduction to JSF 

Topics:

1 What is JSF

2. A JSF application

3. Value and Method Binding

4. Prerequisites to use JSF

5. JSF Main features

1. What is JSF

JavaServer Faces (JSF) is a UI component based Java Web application framework. JSF is serverbased, e.g. the JSF UI components and their state are represented on the server with a defined life cycle of the UI components. JSF is part of the Java EE standard. 

A JSF application run in a standard web container, for example Tomcat or Jetty. 

2. A JSF application

A JSF application consists of web pages with JSF UI components. A JSF application requires also some configuration files ("faces-config.xml" and web.xml). 

The faces-config.xml defines:

• Managed Bean - the data elements of the JSF application (managed beans and backing beans) Represents a Java class which will be created dynamically during runtime of the JSF application. It can be defined for which scope the bean is valid (Session, Request, Application or none).
  
• the navigation between web pages
  
• data validators - Used to check the validity of UI input
  
• data converters -Used to translate between UI and model
  

Managed beans are simple Java objects (POJO's) which are declared in "faces-config.xml" and can be used in an JSF application. For example you can define a Java object "Person". Once you define the object in faces-config.xml you can use the attributes of Person in your JSF UI components, e.g. by binding the value "firstName" of this object to an JSF input field.

JSF uses the Unified Expression Language (EL) to bind UI components to object attributes or methods.

3. Value and Method Binding

In JSF you can access the values of a managed bean via value binding. For value binding the universal Expression Language (EL) is used (to access bean and / or methods). In JSF you do not need to specify the get() or set() method but just the variable name.
Method binding can be used to bind a JSF component, e.g. a button to an method of a Java class.

Tip

Expression Language statements either start with "${" or with "#{" and end with "}". JSP EL expressions are using the ${...} syntax. These EL expressions are immediately evaluated. JSF EL expressions are of the type #{...}. These are only evaluated when needed (and otherwise stored as strings).

4. Prerequisites to use JSF

To use JSF you need:

• JSF Implementation (in the form of the JSF jars)
  
• The JSTL tags library
  
• A Java runtime environment
  
• A web-container to use JSF in (for example Tomcat)
  

5. JSF Main features

JSF has the following main features:

• JSF is based on the Model-View-Controller concept
  
• JSF has a stateful UI component model, e.g. each component is aware of its data
  
• JSF separates the functionality of a component from the display of the component. The renderer is responsible of displaying the component for a certain client. This renderer can get exchanged. The standard renderer for JSF components is the HTML renderer.
  
• JSF support listeners on UI components
  
• JSF support data validation, data binding and data conversion between the UI and the model