JSF Lifecycle Phases
JSF follows MVC design pattern to handle request-response process.Basically JSF handles three types of requests.
A JavaServer Faces page is represented by a tree of UI components, called a view. When a client makes a request for the page, the life cycle starts. During the life cycle, the JavaServer Faces implementation must build the view while considering state saved from a previous submission of the page. When the client submits a page, the JavaServer Faces implementation must perform several tasks, such as validating the data input of components in the view and converting input data to types specified on the server side. The JavaServer Faces implementation performs all these tasks as a series of steps in the life cycle.
Scenario 3: Faces Request Generates Faces Response
This scenario involves a JavaServer Faces component submitting a request to a JavaServer Faces application utilizing the
Life Cycle Steps...
Restore View:In this phase, the JSF implementation restores the objects and data structures that represent the view of the request. Of course, if this is the client’s first visit to a page, the JSF implementation must create the view. When a JSF implementation creates and renders a JSF-enabled page, it creates UI objects for each view component. The components are stored in a component tree, and the state of the UI view is saved for subsequent requests. If this is a subsequent request, the previously saved UI view is retrieved for the processing of the current request.
Method Invoked:
Apply Request Values: Any data that was sent as part of the request is passed to the appropriate UI objects that compose the view. Those objects update their state with the data values. Data can come from input fields in a web form, from cookies sent as part of the request, or from request headers. Data for some components, such as components that create HTML input fields, is validated at this time. Note that this does not yet update the business objects that compose the model. It updates only the UI components with the new data.
Process Validations: The data that was submitted with the form is validated (if it was not validated in the previous phase). As with the previous phase, this does not yet update the business objects in the application. This is because if the JSF implementation began to update the business objects as data was validated, and a piece of data failed validation, the model would be partially updated and in an invalid state.
Update Model Values: After all validations are complete, the business objects that make up the application are updated with the validated data from the request. In addition, if any of the data needs to be converted to a different format to update the model (for example, converting a String to a Date object), the conversion occurs in this phase. Conversion is needed when the data type of a property is not a String or a Java primitive.
Invoke Application: During this phase, the action method of any command button or link that was activated is called. In addition, any events that were generated during previous phases and that have not yet been handled are passed to the web application so that it can complete any other processing of the request that is required.
Render Response: The response UI components are rendered, and the response is sent to the client. The state of the UI components is saved so that the component tree can be restored when the client sends another request. For a JSF-enabled application, the thread of execution for a request/response cycle can flow through each phase.
JSF Life Cycle Phases Diagrammatically View.
- Non-Faces Request Generates Faces Response
- Faces Request Generates Non-Faces Response
- Faces Request Generates Faces Response
A JavaServer Faces page is represented by a tree of UI components, called a view. When a client makes a request for the page, the life cycle starts. During the life cycle, the JavaServer Faces implementation must build the view while considering state saved from a previous submission of the page. When the client submits a page, the JavaServer Faces implementation must perform several tasks, such as validating the data input of components in the view and converting input data to types specified on the server side. The JavaServer Faces implementation performs all these tasks as a series of steps in the life cycle.
Scenario 1: Non-Faces Request Generates Faces Response
An example of this scenario occurs when clicking a hyperlink on an HTML page opens a JavaServer Faces page. To render a Faces response from a non-Faces request, an application must provide a mapping toFacesServlet, which accepts incoming requests and passes them to the life cycle implementation for processing.Context will call FacesContext.renderResponse.
Scenario 2: Faces Request Generates Non-Faces Response
Sometimes a JavaServer Faces application might need to redirect to a different web application resource or might need to generate a response that does not contain any JavaServer Faces components. In these situations context will callFacesContext.responseComplete.
Scenario 3: Faces Request Generates Faces Response
This scenario involves a JavaServer Faces component submitting a request to a JavaServer Faces application utilizing the
FacesServlet. Because the request has been handled by the JavaServer Faces implementation, no additional steps are required by the application to generate the response. All listeners, validators and converters will automatically be invoked during the appropriate phase of the standard life cycle
Life Cycle Steps...
Restore View:In this phase, the JSF implementation restores the objects and data structures that represent the view of the request. Of course, if this is the client’s first visit to a page, the JSF implementation must create the view. When a JSF implementation creates and renders a JSF-enabled page, it creates UI objects for each view component. The components are stored in a component tree, and the state of the UI view is saved for subsequent requests. If this is a subsequent request, the previously saved UI view is retrieved for the processing of the current request.
Method Invoked:
Apply Request Values: Any data that was sent as part of the request is passed to the appropriate UI objects that compose the view. Those objects update their state with the data values. Data can come from input fields in a web form, from cookies sent as part of the request, or from request headers. Data for some components, such as components that create HTML input fields, is validated at this time. Note that this does not yet update the business objects that compose the model. It updates only the UI components with the new data.
If any decode methods or event listeners called renderResponse on the current FacesContext instance, the JavaServer Faces implementation skips to the render response phase.
Process Validations: The data that was submitted with the form is validated (if it was not validated in the previous phase). As with the previous phase, this does not yet update the business objects in the application. This is because if the JSF implementation began to update the business objects as data was validated, and a piece of data failed validation, the model would be partially updated and in an invalid state.
Update Model Values: After all validations are complete, the business objects that make up the application are updated with the validated data from the request. In addition, if any of the data needs to be converted to a different format to update the model (for example, converting a String to a Date object), the conversion occurs in this phase. Conversion is needed when the data type of a property is not a String or a Java primitive.
Invoke Application: During this phase, the action method of any command button or link that was activated is called. In addition, any events that were generated during previous phases and that have not yet been handled are passed to the web application so that it can complete any other processing of the request that is required.
Render Response: The response UI components are rendered, and the response is sent to the client. The state of the UI components is saved so that the component tree can be restored when the client sends another request. For a JSF-enabled application, the thread of execution for a request/response cycle can flow through each phase.
JSF Life Cycle Phases Diagrammatically View.
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