JSF Life Cycle - Information

[Harshavardhan Karkar]

Hi All,

Just an information on life cycle of JSF, interesting read...

Life cycle of a JSF web application starts when user makes a request. 

On submission of  a page various further tasks are performed like 

- validation of data provided in components in the view (JSP Page), 

- data conversion according to types specified on server side and much more. 

Series of steps that an application follows is called life cycle.

A JSF Application is initiated by calling the Faces Servlet (configured in the web.xml file), 

The activities taking place will come under the category of JSF Request Processing Life-cycle Phases namely, 

Restore View

- The restore view phase starts upon user requests to a JSF page by clicking a link, button etc. 

- In this phase following things are done namely,

  a. view generation of the page

  b. binding of components to its event handlers and validators are performed 

  c. view is saved in the FacesContext object. 

Apply Request Values

- The purpose of this phase is for each component to retrieve its current state. 

- After restoring of component tree in restore view phase each component in the tree retrieves its new 

   value and store it locally. 

- Component values are typically retrieved from the request parameters.

- If immediate attribute of a component is set to true, then the validation, conversion, and events 

  associated with the component is processed in this phase.

Process Validations 

- Here local values stored for the component in the tree are compared to the validation  rules registered 

  for the components. 

- If local value is invalid, an error message is added to FacesContext, and the component is treated invalid 

   and then JSF proceeds to the render response phase and display the current view showing the validation 

   error messages. 

- If there were conversion errors from the apply request values phase, the messages for these errors are 

  also displayed. 

- If there are no validation errors, JSF proceeds ahead to the update model values phase.

Update Model Values

- After confirming that data is valid in the previous phase local values of components can be set to 

  corresponding server side object properties i.e. backing beans. 

- The bean properties will be updated .If the local data cannot be converted to the types specified by the 

   bean properties, the life cycle proceeds directly to the render response phase and errors are displayed if 

   any during applying to the bean.

Invoke Application

- Before this phase the component values have been converted, validated, and applied to the bean objects.

- These can now be used to execute the application's business logic. 

- Application-level code is executed such as submitting a form or linking to another page.

- For example user moves to the next page you will have to create a mapping in the faces-config.xml file. 

- Once this navigation occurs, you move to the final phase of the lifecycle.

Render Response

- In this phase JSP container renders the page back to the user,if jsp is used by application 

  i.e. view is displayed with all of its components in their current state.

- If this is an initial request, the components will be added to the component tree. 

- If this is not an initial request, the components are not added because they are already added to the tree.

- The state of the response is saved after rendering of the content of the view.

- The subsequent requests can access it and it is available to the restore view phase.

Thanks and Regards

H.M. Karkar 

-------------------------------------------------

Project Manager 

Info-Spectrum India Pvt. Ltd. 

http://www.info-spectrum.com 

http://www.jugnagpur.com