When is a managed bean instantiated

Overview 2. Getting Started with Web Applications 4. JavaServer Faces Technology 5. Introduction to Facelets 6. Expression Language 7. Using Converters, Listeners, and Validators 9. Developing with JavaServer Faces Technology Composite Components: Advanced Topics and Example Java Servlet Technology Uploading Files with Java Servlet Technology Introduction to Web Services Enterprise Beans Getting Started with Enterprise Beans Running the Enterprise Bean Examples A Message-Driven Bean Example Using the Embedded Enterprise Bean Container Running the Persistence Examples The Java Persistence Query Language Getting Started Securing Web Applications Getting Started Securing Enterprise Applications Transactions Resources and Resource Adapters The Resource Adapter Example Java Message Service Concepts Java Message Service Examples Bean Validation: Advanced Topics ManagedBean marks a bean to be a managed bean with the name specified in name attribute.

If the name attribute is not specified, then the managed bean name will default to class name portion of the fully qualified class name. In our case, it would be helloWorld. Another important attribute is eager.

Scope annotations set the scope into which the managed bean will be placed. If the scope is not specified, then bean will default to request scope. Each scope is briefly discussed in the following table. Bean lives as long as the HTTP request-response lives. Bean lives as long as a single EL evaluation.

It gets created upon an EL evaluation and gets destroyed immediately after the EL evaluation. It takes a view definition usually from a file, often in JSP form and compiles it into a tree structure. This structure serves as the basis for invoking the backing bean functions. When an action is invoked, a different View definition may be requested, in which case the old tree is discarded, and a new tree is compiled using the indicated new view definition.

JSF works with discrete rendering engines that take the view tree and the JEE environment including JSF backing beans and runs the selected renderer against that tree. The rendering process may and often will involve calling backing bean getters. Most commonly, the renderer used is the stock HTML renderer, but other renderers are also possible, including user-defined ones. I really recommend you find some good documentation on the JSF lifecycle, and a book or 2 on JSF wouldn't be a bad investment.

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