JSF for Nonbelievers: The JSF Application Lifecycle
By Rick Hightower2005-05-05
Phase 2: Apply Request Values
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The purpose of the apply request values phase is for each component to retrieve its current state. The components must first be retrieved or created from the FacesContext object, followed by their values. Component values are typically retrieved from the request parameters, although they can also be retrieved from cookies or headers.
If a component's immediate event handling property is not set to true, the values are just converted. So if the field is bound to an Integer property, the value is converted to an Integer. If the value conversion fails, an error message is generated and queued in the FacesContext, where it will be displayed during the render response phase, along with any validation errors.
If a component's immediate event handling property is set to true, the values are converted to the proper type and validated. The converted value is then stored in the component. If the value conversion or value validation fails, an error message is generated and queued in the FacesContext, where it will be displayed during the render response phase, along with any other validation errors.
Immediate event handling
The immediate event handling property of JSF is used to handle events that normally don't necessitate validating the entire form. For example, say an employee form has a radio button denoting whether an employee is a manager. When the employee selects the Manager option, the application populates a list of perks for managers. Because the radio button is used only to populate the list and does not require the user to fill out the entire form, you do not need to validate the form in its entirety. In this case, you would use immediate event handling. See Immediate event handling for further details on this subject.
Tutorial Pages:
» Walk Through the 6 Phases of JSF's Request Processing Lifecycle
» The JSF Lifecycle: an Overview
» Phase 1: Restore View
» Phase 2: Apply Request Values
» Phase 3: Process Validation
» Phase 4: Update Model Values
» Phase 5: Invoke application
» Phase 6: Render Response
» A Working Example
» Let's Code it
» Use Case 1: Add a New CD
» Use Case 2: Edit a CD
» Use Case 3: Sort CDs
» Immediate Event Handling
» Conclusion
» Resources
First published by IBM DeveloperWorks
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