JavaServer Faces Interview Questions
What is JSF (or JavaServer Faces)?
A server side user interface component framework for Java™ technology-based web applications.JavaServer Faces (JSF) is an industry standard and a framework for building component-based user interfaces for web applications.
JSF contains an API for representing UI components and managing their state; handling events, server-side validation, and data conversion; defining page navigation; supporting internationalization and accessibility; and providing extensibility for all these features.
2. What are the advantages of JSF?
The major benefits of JavaServer Faces technology are:
- JavaServer Faces architecture makes it easy for the developers to use. In JavaServer Faces technology, user interfaces can be created easily with its built-in UI component library, which handles most of the complexities of user interface management.
- Offers a clean separation between behavior and presentation.
- Provides a rich architecture for managing component state, processing component data, validating user input, and handling events.
- Robust event handling mechanism.
- Events easily tied to server-side code.
- Render kit support for different clients
- Component-level control over statefulness
- Highly 'pluggable' - components, view handler, etc
- JSF also supports internationalization and accessibility
- Offers multiple, standardized vendor implementations
3. What are differences between struts and JSF?
In a nutshell, Faces has the following advantages over Struts:
Eliminated the need for a Form Bean
Eliminated the need for a DTO Class
Allows the use of the same POJO on all Tiers because of the Backing Bean
Because Struts is a web application framework, it has a more sophisticated controller architecture than does JavaServer Faces technology. It is more sophisticated partly because the application developer can access the controller by creating an Action object that can integrate with the controller, whereas JavaServer Faces technology does not allow access to the controller. In addition, the Struts controller can do things like access control on each Action based on user roles. This functionality is not provided by JavaServer Faces technology.
Struts includes a powerful layout management framework, called Tiles, which allows you to create templates that you can reuse across multiple pages, thus enabling you to establish an overall look-and-feel for an application.
The Struts validation framework includes a larger set of standard validators, which automatically generate both server-side and client-side validation code based on a set of rules in a configuration file. You can also create custom validators and easily include them in your application by adding definitions of them in your configuration file.
A standard component API for specifying the state and behavior of a wide range of components, including simple components, such as input fields, and more complex components, such as scrollable data tables. Developers can also create their own components based on these APIs, and many third parties have already done so and have made their component libraries publicly available.
A separate rendering model that defines how to render the components in various ways. For example, a component used for selecting an item from a list can be rendered as a menu or a set of radio buttons.
An event and listener model that defines how to handle events generated by activating a component, such as what to do when a user clicks a button.
Conversion and validation models for converting and validating component data.
What are the available implementations of JavaServer Faces?
The main implementations of JavaServer Faces are:
- Reference Implementation (RI) by Sun Microsystems.
- Apache MyFaces is an open source JavaServer Faces (JSF) implementation or run-time.
- ADF Faces is Oracle’s implementation for the JSF standard.
6. What typical JSF application consists of?
A typical JSF application consists of the following parts:
- JavaBeans components for managing application state and behavior.
- Event-driven development (via listeners as in traditional GUI development).
- Pages that represent MVC-style views; pages reference view roots via the JSF component tree.
7. What Is a JavaServer Faces Application?
JavaServer Faces applications are just like any other Java web application. They run in a servlet container, and they typically contain the following:
- JavaBeans components containing application-specific functionality and data.
- Event listeners.
- Pages, such as JSP pages.
- Server-side helper classes, such as database access beans.
- A custom tag library for rendering UI components on a page.
- A custom tag library for representing event handlers, validators, and other actions.
- UI components represented as stateful objects on the server.
- Backing beans, which define properties and functions for UI components.
- Validators, converters, event listeners, and event handlers.
- An application configuration resource file for configuring application resources.
8. What is Managed Bean?
JavaBean objects managed by a JSF implementation are called managed beans. A managed bean describes how a bean is created and managed. It has nothing to do with the bean's functionalities.
9. What is Backing Bean?
Backing beans are JavaBeans components associated with UI components used in a page. Backing-bean management separates the definition of UI component objects from objects that perform application-specific processing and hold data.
The backing bean defines properties and handling-logics associated with the UI components used on the page. Each backing-bean property is bound to either a component instance or its value. A backing bean also defines a set of methods that perform functions for the component, such as validating the component's data, handling events that the component fires and performing processing associated with navigation when the component activates.
10. What are the differences between a Backing Bean and Managed Bean?
Backing Beans are merely a convention, a subtype of JSF Managed Beans which have a very particular purpose. There is nothing special in a Backing Bean that makes it different from any other managed bean apart from its usage.
What makes a Backing Bean is the relationship it has with a JSF page; it acts as a place to put component references and Event code.
|A backing bean is any bean that is referenced by a form.
||A managed bean is a backing bean that has been registered with JSF (in faces-config.xml) and it automatically created (and optionally initialized) by JSF when it is needed.
||The advantage of managed beans is that the JSF framework will automatically create these beans, optionally initialize them with parameters you specify in faces-config.xml,
|Backing Beans should be defined only in the request scope
||The managed beans that are created by JSF can be stored within the request, session, or application scopes
Backing Beans should be defined in the request scope, exist in a one-to-one relationship with a particular page and hold all of the page specific event handling code.In a real-world scenario, several pages may need to share the same backing bean behind the scenes.A backing bean not only contains view data, but also behavior related to that data.
11. What is view object?
A view object is a model object used specifically in the presentation tier. It contains the data that must display in the view layer and the logic to validate user input, handle events, and interact with the business-logic tier. The backing bean is the view object in a JSF-based application. Backing bean and view object are interchangeable terms.