ViewHandler (Java EE 5 SDK) - Java Platform, Enterprise Edition v5.0 API Specifications

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javax.faces.application
Class ViewHandler

java.lang.Object
  javax.faces.application.ViewHandler

Direct Known Subclasses:: ViewHandlerWrapper

public abstract class ViewHandler
extends Object
extends Object

ViewHandler is the pluggablity mechanism for allowing implementations of or applications using the JavaServer Faces specification to provide their own handling of the activities in the Render Response and Restore View phases of the request processing lifecycle. This allows for implementations to support different response generation technologies, as well as alternative strategies for saving and restoring the state of each view.

Please see StateManager for information on how the ViewHandler interacts the StateManager.

Field Summary

static String CHARACTER_ENCODING_KEY
          The key, in the session's attribute set, under which the response character encoding may be stored and retrieved.

static String DEFAULT_SUFFIX
          The value to use for the default extension if the webapp is using url extension mapping.

static String DEFAULT_SUFFIX_PARAM_NAME
          Allow the web application to define an alternate suffix for pages containing JSF content.

Constructor Summary

ViewHandler()


Method Summary

String calculateCharacterEncoding(FacesContext context)
          Returns the correct character encoding to be used for this request.

abstract Locale calculateLocale(FacesContext context)
          Returns an appropriate Locale to use for this and subsequent requests for the current client.

abstract String calculateRenderKitId(FacesContext context)
          Return an appropriate renderKitId for this and subsequent requests from the current client.

abstract UIViewRoot createView(FacesContext context, String viewId)
          Create and return a new UIViewRoot instance initialized with information from the argument FacesContext and viewId.

abstract String getActionURL(FacesContext context, String viewId)
          Return a URL suitable for rendering (after optional encoding performed by the encodeActionURL() method of ExternalContext) that selects the specified view identifier.

abstract String getResourceURL(FacesContext context, String path)
          Return a URL suitable for rendering (after optional encoding perfomed by the encodeResourceURL() method of ExternalContext) that selects the specifed web application resource.

void initView(FacesContext context)
          Initialize the view for the request processing lifecycle.

abstract void renderView(FacesContext context, UIViewRoot viewToRender)
          Perform whatever actions are required to render the response view to the response object associated with the current FacesContext.

abstract UIViewRoot restoreView(FacesContext context, String viewId)
          Perform whatever actions are required to restore the view associated with the specified FacesContext and viewId.

abstract void writeState(FacesContext context)
          Take any appropriate action to either immediately write out the current state information (by calling StateManager.writeState(javax.faces.context.FacesContext, java.lang.Object), or noting where state information should later be written.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Summary
`static String`	`CHARACTER_ENCODING_KEY` The key, in the session's attribute set, under which the response character encoding may be stored and retrieved.
`static String`	`DEFAULT_SUFFIX` The value to use for the default extension if the webapp is using url extension mapping.
`static String`	`DEFAULT_SUFFIX_PARAM_NAME` Allow the web application to define an alternate suffix for pages containing JSF content.

Constructor Summary
`ViewHandler()`

Method Summary
`String`	`calculateCharacterEncoding(FacesContext context)` Returns the correct character encoding to be used for this request.
`abstract Locale`	`calculateLocale(FacesContext context)` Returns an appropriate `Locale` to use for this and subsequent requests for the current client.
`abstract String`	`calculateRenderKitId(FacesContext context)` Return an appropriate `renderKitId` for this and subsequent requests from the current client.
`abstract UIViewRoot`	`createView(FacesContext context, String viewId)` Create and return a new `UIViewRoot` instance initialized with information from the argument `FacesContext` and `viewId`.
`abstract String`	`getActionURL(FacesContext context, String viewId)` Return a URL suitable for rendering (after optional encoding performed by the `encodeActionURL()` method of `ExternalContext`) that selects the specified view identifier.
`abstract String`	`getResourceURL(FacesContext context, String path)` Return a URL suitable for rendering (after optional encoding perfomed by the `encodeResourceURL()` method of `ExternalContext`) that selects the specifed web application resource.
`void`	`initView(FacesContext context)` Initialize the view for the request processing lifecycle.
`abstract void`	`renderView(FacesContext context, UIViewRoot viewToRender)` Perform whatever actions are required to render the response view to the response object associated with the current `FacesContext`.
`abstract UIViewRoot`	`restoreView(FacesContext context, String viewId)` Perform whatever actions are required to restore the view associated with the specified `FacesContext` and `viewId`.
`abstract void`	`writeState(FacesContext context)` Take any appropriate action to either immediately write out the current state information (by calling `StateManager.writeState(javax.faces.context.FacesContext, java.lang.Object)`, or noting where state information should later be written.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

CHARACTER_ENCODING_KEY

public static final String CHARACTER_ENCODING_KEY

The key, in the session's attribute set, under which the response character encoding may be stored and retrieved.

See Also:: Constant Field Values

DEFAULT_SUFFIX_PARAM_NAME

public static final String DEFAULT_SUFFIX_PARAM_NAME

Allow the web application to define an alternate suffix for pages containing JSF content. If this init parameter is not specified, the default value is taken from the value of the constant DEFAULT_SUFFIX.

See Also:: Constant Field Values

DEFAULT_SUFFIX

public static final String DEFAULT_SUFFIX

The value to use for the default extension if the webapp is using url extension mapping.

See Also:: Constant Field Values

Constructor Detail

ViewHandler

public ViewHandler()

Method Detail

calculateLocale

public abstract Locale calculateLocale(FacesContext context)

Returns an appropriate Locale to use for this and subsequent requests for the current client.

Parameters:: context - FacesContext for the current request
Throws:: NullPointerException - if context is null

calculateCharacterEncoding

public String calculateCharacterEncoding(FacesContext context)

Returns the correct character encoding to be used for this request.

The following algorithm is employed.

Examine the Content-Type request header. If it has a charset parameter, extract it and return that as the encoding.
If no charset parameter was found, check for the existence of a session by calling ExternalContext.getSession(boolean) passing false as the argument. If that method returns true, get the session Map by calling ExternalContext.getSessionMap() and look for a value under the key given by the value of the symbolic constant CHARACTER_ENCODING_KEY. If present, return the value, converted to String.
Otherwise, return null

calculateRenderKitId

public abstract String calculateRenderKitId(FacesContext context)

Return an appropriate renderKitId for this and subsequent requests from the current client. It is an error for this method to return null.

The default return value is RenderKitFactory.HTML_BASIC_RENDER_KIT.

Parameters:: context - FacesContext for the current request
Throws:: NullPointerException - if context is null

createView

public abstract UIViewRoot createView(FacesContext context,
                                      String viewId)

Create and return a new UIViewRoot instance initialized with information from the argument FacesContext and viewId.

If there is an existing ViewRoot available on the FacesContext, this method must copy its locale and renderKitId to this new view root. If not, this method must call calculateLocale(javax.faces.context.FacesContext) and calculateRenderKitId(javax.faces.context.FacesContext), and store the results as the values of the locale and renderKitId, proeprties, respectively, of the newly created UIViewRoot.

Throws:: NullPointerException - if context is null

getActionURL

public abstract String getActionURL(FacesContext context,
                                    String viewId)

Return a URL suitable for rendering (after optional encoding performed by the encodeActionURL() method of ExternalContext) that selects the specified view identifier.

Parameters:: context - FacesContext for this request; viewId - View identifier of the desired view
Throws:: IllegalArgumentException - if viewId is not valid for this ViewHandler.; NullPointerException - if context or viewId is null.

getResourceURL

public abstract String getResourceURL(FacesContext context,
                                      String path)

Return a URL suitable for rendering (after optional encoding perfomed by the encodeResourceURL() method of ExternalContext) that selects the specifed web application resource. If the specified path starts with a slash, it must be treated as context relative; otherwise, it must be treated as relative to the action URL of the current view.

Parameters:: context - FacesContext for the current request; path - Resource path to convert to a URL
Throws:: IllegalArgumentException - if viewId is not valid for this ViewHandler.; NullPointerException - if context or path is null.

initView

public void initView(FacesContext context)
              throws FacesException

Initialize the view for the request processing lifecycle.

This method must be called at the beginning of the Restore View Phase of the Request Processing Lifecycle. It is responsible for performing any per-request initialization necessary to the operation of the lifycecle.

The default implementation calls calculateCharacterEncoding(javax.faces.context.FacesContext) and passes the result, if non-null into the ExternalContext.setRequestCharacterEncoding(java.lang.String) method.

Throws:: FacesException - if a problem occurs setting the encoding, such as the UnsupportedEncodingException thrown by the underlying Servlet or Portlet technology when the encoding is not supported.

renderView

public abstract void renderView(FacesContext context,
                                UIViewRoot viewToRender)
                         throws IOException,
                                FacesException

Perform whatever actions are required to render the response view to the response object associated with the current FacesContext.

Parameters:: context - FacesContext for the current request; viewToRender - the view to render
Throws:: IOException - if an input/output error occurs; NullPointerException - if context or viewToRender is null; FacesException - if a servlet error occurs

restoreView

public abstract UIViewRoot restoreView(FacesContext context,
                                       String viewId)

Perform whatever actions are required to restore the view associated with the specified FacesContext and viewId. It may delegate to the restoreView of the associated StateManager to do the actual work of restoring the view. If there is no available state for the specified viewId, return null.

Parameters:: context - FacesContext for the current request; viewId - the view identifier for the current request
Throws:: NullPointerException - if context is null; FacesException - if a servlet error occurs

writeState

public abstract void writeState(FacesContext context)
                         throws IOException

Take any appropriate action to either immediately write out the current state information (by calling StateManager.writeState(javax.faces.context.FacesContext, java.lang.Object), or noting where state information should later be written.

Parameters:: context - FacesContext for the current request
Throws:: IOException - if an input/output error occurs; NullPointerException - if context is null