Package jakarta.faces.application

Class ViewHandler

java.lang.Object
jakarta.faces.application.ViewHandler
Direct Known Subclasses:
ViewHandlerWrapper
public abstract class ViewHandler extends Object

ViewHandler is the pluggablity mechanism for allowing implementations of or applications using the Jakarta 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. An implementation of this class must be thread-safe.

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

Version 2 of the specification formally introduced the concept of View Declaration Language. A View Declaration Language (VDL) is a syntax used to declare user interfaces comprised of instances of Jakarta Faces UIComponents. Any of the responsibilities of the ViewHandler that specifically deal with the VDL sub-system are now the domain of the VDL implementation. These responsibilities are defined on the ViewDeclarationLanguage class. The ViewHandler provides getViewDeclarationLanguage(jakarta.faces.context.FacesContext, java.lang.String) as a convenience method to access the VDL implementation given a viewId.

  • Field Details

    • 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:

    • DEFAULT_SUFFIX_PARAM_NAME

      @Deprecated(since="4.0", forRemoval=true) public static final String DEFAULT_SUFFIX_PARAM_NAME
      Deprecated, for removal: This API element is subject to removal in a future version.
      Use FACELETS_SUFFIX_PARAM_NAME instead.

      This is not anymore used since removal of support for Jakarta Pages.

      See Also:

    • DEFAULT_SUFFIX

      @Deprecated(since="4.0", forRemoval=true) public static final String DEFAULT_SUFFIX
      Deprecated, for removal: This API element is subject to removal in a future version.
      Use DEFAULT_FACELETS_SUFFIX instead.

      This is not anymore used since removal of support for Jakarta Pages.

      See Also:

    • FACELETS_SKIP_COMMENTS_PARAM_NAME

      public static final String FACELETS_SKIP_COMMENTS_PARAM_NAME

      If this param is set, and calling toLowerCase().equals("true") on a String representation of its value returns true, the runtime must ensure that any XML comments in the Facelets source page are not delivered to the client.

      Since:
      2.0
      See Also:

    • FACELETS_SUFFIX_PARAM_NAME

      public static final String FACELETS_SUFFIX_PARAM_NAME

      Allow the web application to define a list of alternate suffixes for Facelet based XHTML pages containing Jakarta Faces content. This list is a space separated list of values of the form .<extension>. The first physical resource whose extension matches one of the configured extensions will be the suffix used to create the view ID. If this init parameter is not specified, the default value is taken from the value of the constant DEFAULT_FACELETS_SUFFIX

      Since:
      2.0
      See Also:

    • DEFAULT_FACELETS_SUFFIX

      public static final String DEFAULT_FACELETS_SUFFIX

      The value to use for the default extension for Facelet based XHTML pages if the webapp is using url extension mapping.

      Since:
      2.0
      See Also:

    • FACELETS_VIEW_MAPPINGS_PARAM_NAME

      public static final String FACELETS_VIEW_MAPPINGS_PARAM_NAME

      Allow the web application to define a semicolon (;) separated list of strings that is used to forcibly declare that certain pages in the application must be interpreted as using Facelets, regardless of their extension. Each entry in the semicolon (;) separated list of strings is either a file extension, as in *.xhtml, or a resource prefix (starting with '/' and interpreted as relative to the web application root), as in /user/*. The latter class of entry can also take the form of /<filename>.<extension>* such as /login.xhtml*.

      Since:
      2.0
      See Also:

    • FACELETS_BUFFER_SIZE_PARAM_NAME

      public static final String FACELETS_BUFFER_SIZE_PARAM_NAME

      The buffer size to set on the response when the ResponseWriter is generated. By default the value is 1024. A value of -1 will not assign a buffer size on the response. This should be increased if you are using development mode in order to guarantee that the response isn't partially rendered when an error is generated.

      Since:
      2.0
      See Also:

    • FACELETS_REFRESH_PERIOD_PARAM_NAME

      public static final String FACELETS_REFRESH_PERIOD_PARAM_NAME

      When a page is requested, what interval in seconds should the compiler check for changes. If you don't want the compiler to check for changes once the page is compiled, then use a value of -1. Setting a low refresh period helps during development to be able to edit pages in a running application. If this value is not specified, then the default depends on ProjectStage. If it is Production, then runtime must act as if it is set to -1, else the runtime must act as if it is set to 0.

      Since:
      2.0
      See Also:

    • FACELETS_LIBRARIES_PARAM_NAME

      public static final String FACELETS_LIBRARIES_PARAM_NAME

      If this param is set, the runtime must interpret it as a semicolon (;) separated list of paths, starting with "/" (without the quotes). The runtime must interpret each entry in the list as a path relative to the web application root and interpret the file found at that path as a facelet tag library, conforming to the facelet taglibrary schema and expose the tags therein according to Section "Facelet Tag Library mechanism".

      Since:
      2.0
      See Also:

    • FACELETS_DECORATORS_PARAM_NAME

      public static final String FACELETS_DECORATORS_PARAM_NAME

      A semicolon (;) delimitted list of class names of type jakarta.faces.view.facelets.TagDecorator, with a no-argument constructor. These decorators will be loaded when the first request for a Facelets VDL view hits the ViewHandler for page compilation.

      Since:
      2.0
      See Also:

  • Constructor Details

    • ViewHandler

      public ViewHandler()

  • Method Details

    • 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 must perform the following actions. If ExternalContext.getRequestCharacterEncoding() returns null, call calculateCharacterEncoding(jakarta.faces.context.FacesContext) and pass the result, if non-null, into the ExternalContext.setRequestCharacterEncoding(java.lang.String) method. If ExternalContext.getRequestCharacterEncoding() returns non-null take no action.

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

    • 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.

      Otherwise, the default implementation must obtain a reference to the ViewDeclarationLanguage for this viewId and call its ViewDeclarationLanguage.restoreView(jakarta.faces.context.FacesContext, java.lang.String) method, returning the result and not swallowing any exceptions thrown by that method.

      Parameters:
      context - FacesContext for the current request
      viewId - the view identifier for the current request
      Returns:
      the restored view root, or null.
      Throws:
      NullPointerException - if context is null
      FacesException - if a Jakarta Servlet error occurs

    • 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. Locate the ViewDeclarationLanguage implementation for the VDL used in the view. The argument viewId must be converted to a physical viewId that can refer to an actual resource suitable for use by the ViewDeclarationLanguage ViewDeclarationLanguage.createView(jakarta.faces.context.FacesContext, java.lang.String), which must be called by this method.

      Parameters:
      context - the Faces context.
      viewId - the view id.
      Returns:
      the viewroot.
      Throws:
      NullPointerException - if context is null

    • 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.

      Otherwise, the default implementation must obtain a reference to the ViewDeclarationLanguage for the viewId of the argument viewToRender and call its ViewDeclarationLanguage.renderView(jakarta.faces.context.FacesContext, jakarta.faces.component.UIViewRoot) method, returning the result and not swallowing any exceptions thrown by that method.

      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 Jakarta Servlet error occurs

    • 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
      Returns:
      the locale.
      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

      Parameters:
      context - the Faces context.
      Returns:
      the character encoding, or null
      Since:
      1.2

    • 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
      Returns:
      the render kit id.
      Throws:
      NullPointerException - if context is null

    • deriveViewId

      public String deriveViewId(FacesContext context, String requestViewId)

      Derive and return the viewId from the current request, or the argument input by following the algorithm defined in section 7.6.2 "Default ViewHandler Implementation" of the Jakarta Faces Specification Document.

      This method should work correctly when the FacesServlet is invoked via either a path mapping, extension mapping or an exact match (mapping) as defined by Servlet.12.2. Note that path mapping is also commonly known as prefix mapping (e.g. "/faces/*") and extension mapping as suffix mapping (e.g. "*.xhtml"). An exact match is possible where there's a servlet mapping with an exact URL pattern such as "/foo".

      The default implementation of this method simply returns requestViewId unchanged.

      Parameters:
      context - the FacesContext for this request
      requestViewId - the viewId to derive,
      Returns:
      the derived view id.
      Since:
      2.0

    • deriveLogicalViewId

      public String deriveLogicalViewId(FacesContext context, String requestViewId)

      Derive and return the viewId from the current request, or the argument input by following the algorithm defined in section 7.6.2 "Default ViewHandler Implementation" of the Jakarta Faces Specification Document. Note that unlike deriveViewId(), this method does not require that a physical view be present.

      This method should work correctly when the FacesServlet is invoked via either a path mapping, extension mapping or an exact match (mapping) as defined by Servlet.12.2. Note that path mapping is also commonly known as prefix mapping (e.g. "/faces/*") and extension mapping as suffix mapping (e.g. "*.xhtml"). An exact match is possible where there's a servlet mapping with an exact URL pattern such as "/foo".

      The default implementation of this method simply returns requestViewId unchanged.

      Parameters:
      context - the FacesContext for this request
      requestViewId - the viewId to derive,
      Returns:
      the derived logical view id.
      Since:
      2.1

    • getActionURL

      public abstract String getActionURL(FacesContext context, String viewId)

      If the value returned from this method is used as the file argument to the four-argument constructor for java.net.URL (assuming appropriate values are used for the first three arguments), then a client making a request to the toExternalForm() of that URL will select the argument viewId for traversing the Jakarta Faces lifecycle. Please see section 7.6.2 "Default ViewHandler Implementation" of the Jakarta Faces Specification Document for the complete specification, especially for details related to view protection using the ResponseStateManager.NON_POSTBACK_VIEW_TOKEN_PARAM and the behavior when the current request is to a URL for which the FacesServlet has an exact mapping as defined by Servlet.12.2.

      Parameters:
      context - FacesContext for this request
      viewId - View identifier of the desired view
      Returns:
      the action url.
      Throws:
      IllegalArgumentException - if viewId is not valid for this ViewHandler, or does not start with "/".
      NullPointerException - if context or viewId is null.

    • getRedirectURL

      public String getRedirectURL(FacesContext context, String viewId, Map<String,List<String>> parameters, boolean includeViewParams)

      Return a Jakarta Faces action URL derived from the viewId argument that is suitable to be used by the NavigationHandler to issue a redirect request to the URL using a NonFaces request. Compliant implementations must implement this method as specified in section 7.6.2 "Default ViewHandler Implementation" of the Jakarta Faces Specification Document. The default implementation simply calls through to getActionURL(jakarta.faces.context.FacesContext, java.lang.String), passing the arguments context and viewId.

      Parameters:
      context - The FacesContext processing this request
      viewId - The view identifier of the target page
      parameters - A mapping of parameter names to one or more values
      includeViewParams - A flag indicating whether view parameters should be encoded into this URL
      Returns:
      the redirect URL.
      Since:
      2.0

    • getBookmarkableURL

      public String getBookmarkableURL(FacesContext context, String viewId, Map<String,List<String>> parameters, boolean includeViewParams)

      Return a Jakarta Faces action URL derived from the viewId argument that is suitable to be used as the target of a link in a Jakarta Faces response. Compliant implementations must implement this method as specified in section 7.6.2 "Default ViewHandler Implementation" of the Jakarta Faces Specification Document. The default implementation simply calls through to getActionURL(jakarta.faces.context.FacesContext, java.lang.String), passing the arguments context and viewId.

      Parameters:
      context - The FacesContext processing this request
      viewId - The view identifier of the target page
      parameters - A mapping of parameter names to one or more values
      includeViewParams - A flag indicating whether view parameters should be encoded into this URL
      Returns:
      the bookmarkable URL.
      Since:
      2.0

    • getResourceURL

      public abstract String getResourceURL(FacesContext context, String path)

      If the value returned from this method is used as the file argument to the four-argument constructor for java.net.URL (assuming appropriate values are used for the first three arguments), then a client making a request to the toExternalForm() of that URL will select the argument path for direct rendering. 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
      Returns:
      the resource URL.
      Throws:
      IllegalArgumentException - if viewId is not valid for this ViewHandler.
      NullPointerException - if context or path is null.

    • getWebsocketURL

      public abstract String getWebsocketURL(FacesContext context, String channel)

      If the value returned from this method is used as the file argument to the four-argument constructor for java.net.URL (assuming appropriate values are used for the first three arguments), then a client making a push handshake request to the toExternalForm() of that URL will select the argument channel for connecting the websocket push channel in the current view. It must match the PushContext.URI_PREFIX of the endpoint.

      Parameters:
      context - FacesContext for the current request.
      channel - The channel name of the websocket.
      Returns:
      the websocket URL.
      Throws:
      NullPointerException - if context or channel is null.
      See Also:

    • getProtectedViewsUnmodifiable

      public Set<String> getProtectedViewsUnmodifiable()

      Return an unmodifiable Set of the protected views currently known to this ViewHandler instance. Compliant implementations must return a Set that is the concatenation of the contents of all the <url-pattern> elements within all the <protected-views> in all of the application configuration resources in the current application. The runtime must support calling this method at any time after application startup. The default implementation returns an unmodifiable empty Set.

      Returns:
      the unmodifiable set of protected views.
      Since:
      2.2

    • addProtectedView

      public void addProtectedView(String urlPattern)

      Add the argument urlPattern to the thread safe Set of protected views for this application. Compliant implementations make it so a subsequent call to getProtectedViewsUnmodifiable() contains the argument. The runtime must support calling this method at any time after application startup. The default implementation takes no action.

      Parameters:
      urlPattern - the url-pattern to add.
      Since:
      2.2

    • removeProtectedView

      public boolean removeProtectedView(String urlPattern)

      Remove the argument urlPattern from the thread safe Set of protected views for this application, if present in the Set. If the argument urlPattern is not present in the Set, this method has no effect. Compliant implementations must make it so a subsequent call to getProtectedViewsUnmodifiable() does not contain the argument. The runtime must support calling this method at any time after application startup. Returns true if this Set contained the argument. The default implementation takes no action and returns false.

      Parameters:
      urlPattern - the url-pattern to remove.
      Returns:
      true if in the Set, false otherwise.
      Since:
      2.2

    • getViewDeclarationLanguage

      public ViewDeclarationLanguage getViewDeclarationLanguage(FacesContext context, String viewId)

      Return the ViewDeclarationLanguage instance used for this ViewHandler instance.

      The default implementation must use ViewDeclarationLanguageFactory.getViewDeclarationLanguage(java.lang.String) to obtain the appropriate ViewDeclarationLanguage implementation for the argument viewId. Any exceptions thrown as a result of invoking that method must not be swallowed.

      The default implementation of this method returns null.

      Parameters:
      context - the FacesContext for this request.
      viewId - the logical view id, as returned from deriveLogicalViewId(jakarta.faces.context.FacesContext, java.lang.String) for which the ViewDeclarationLanguage should be returned.
      Returns:
      the ViewDeclarationLanguage, or null.
      Since:
      2.0

    • getViews

      public Stream<String> getViews(FacesContext facesContext, String path, int maxDepth, ViewVisitOption... options)

      Return a Stream possibly lazily populated by walking the view trees of every active ViewDeclarationLanguage rooted at a given initial path. The view tree of every ViewDeclarationLanguage is individually traversed breadth-first as per the contract of ViewDeclarationLanguage.getViews(FacesContext, String, int, ViewVisitOption...). The elements in the stream are logical view ids.

      The maxDepth parameter is the maximum depth of directory levels to visit for each ViewDeclarationLanguage beyond the initial path, which is always visited. The value is relative to the root (/), not to the given initial path. E.g. given maxDepth = 3 and initial path /foo/, visiting will proceed up to /foo/bar/, where / counts as depth 1, /foo/ as depth 2 and /foo/bar/ as depth 3. A value lower or equal to the depth of the initial path means that only the initial path is visited. A value of MAX_VALUE may be used to indicate that all levels should be visited.

      In case more than one active ViewDeclarationLanguage is present, the order in which view ids from each ViewDeclarationLanguage appear in the stream is undetermined, except for the guarantee that every individual ViewDeclarationLanguage is traversed breadth-first.

      Parameters:
      facesContext - The FacesContext for this request.
      path - The initial path from which to start looking for view ids.
      maxDepth - The absolute maximum depth of nested directories to visit counted from the root (/).
      options - The options to influence the traversal. See ViewVisitOption for details on those.
      Returns:
      the Stream of view ids
      Since:
      2.3

    • getViews

      public Stream<String> getViews(FacesContext facesContext, String path, ViewVisitOption... options)

      Return a Stream possibly lazily populated by walking the view trees of every active ViewDeclarationLanguage rooted at a given initial path. The view tree of every ViewDeclarationLanguage is individually traversed breadth-first as per the contract of ViewDeclarationLanguage.getViews(FacesContext, String, int, ViewVisitOption...). The elements in the stream are logical view ids.

      This method works as if invoking it were equivalent to evaluating the expression: 

       getViews(facesContext, start, Integer.MAX_VALUE, options)
      Put differently, it visits all levels of the view tree.

      In case more than one active ViewDeclarationLanguage is present, the order in which view ids from each ViewDeclarationLanguage appear in the stream is undetermined, except for the guarantee that every individual ViewDeclarationLanguage is traversed breadth-first.

      Parameters:
      facesContext - The FacesContext for this request.
      path - The initial path from which to start looking for view ids.
      options - The options to influence the traversal. See ViewVisitOption for details on those.
      Returns:
      the Stream of view ids
      Since:
      2.3

    • 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(jakarta.faces.context.FacesContext, java.lang.Object), or noting where state information should later be written.

      This method must do nothing if the current request is an Ajax request. When responding to Ajax requests, the state is obtained by calling StateManager.getViewState(jakarta.faces.context.FacesContext) and then written into the Ajax response during final encoding (PartialViewContext.processPartial(jakarta.faces.event.PhaseId)) .

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