JSF 除了事件处理之外，总共必须经过六个阶段：
1、恢复视图阶段 Restore View Phase
2、应用请求值阶段 Apply Request Value Phase
3、验证阶段 Process Validation Phase
4、更新模型值阶段 Update Model Values Phase
5、调用应用程序阶段 Invoke Application Phase
6、渲染阶段 Render Response Phase
这六个阶段分别对应六个执行器 RestoreViewExecutor，ApplyRequestValuesExecutor，ProcessValidationsExecutor， UpdateModelValuesExecutor，InvokeApplicationExecutor，RenderResponseExecutor，且都与生命周期对象（LifecycleImpl）耦合。
在此，主要先说下第一阶段，恢复视图阶段 Restore View Phase主要做了什么，起了什么作用？
在项目中引入JSF的是javax.faces.webapp.FacesServlet类,其关联了javax.faces.lifecycle.Lifecycle,所以在JSF中生命周期的
概念是非常重要的，一直贯穿一个请求的始终。而在LIfecycle的实现类LifecycleImpl中又关联了PhaseExecutor类（是一个数组）,包括： RestoreViewExecutor、ApplyRequestValuesExecutor、ProcessValidationsExecutor、 UpdateModelValuesExecutor、 InvokeApplicationExecutor、RenderResponseExecutor,这六个类共同继承了PhaseExecutor。其中RenderResponseExecutor是作一个单独的属性进行关联的。
接下来我们来先看一段RestoreViewExecutor类中的核心代码:
public boolean execute(FacesContext facesContext)
{
if (facesContext == null)
{
throw new FacesException("FacesContext is null");
}
// get some required Objects
Application application = facesContext.getApplication();
ViewHandler viewHandler = application.getViewHandler();
UIViewRoot viewRoot = facesContext.getViewRoot();
RestoreViewSupport restoreViewSupport = getRestoreViewSupport(facesContext);
// Examine the FacesContext instance for the current request. If it already contains a UIViewRoot
if (viewRoot != null)
{
if (log.isLoggable(Level.FINEST))
{
log.finest("View already exists in the FacesContext");
}
// Set the locale on this UIViewRoot to the value returned by the getRequestLocale() method on the
// ExternalContext for this request
viewRoot.setLocale(facesContext.getExternalContext().getRequestLocale());
restoreViewSupport.processComponentBinding(facesContext, viewRoot);
// invoke the afterPhase MethodExpression of UIViewRoot
_invokeViewRootAfterPhaseListener(facesContext);
return false;
}
.......
首先在JSF上下文中寻找组件树（UIViewRoot），如果找到则说明视图已经存在于上下文中，这时主要做了以下几件事：
1)、把当前请求的Lacale赋给组件树。
2)、执行组件树与EL表达式的绑定。？
在这里RestoreViewExecutor关联了RestoreViewSupport类，调用了该类的一个方法：processComponentBinding
这个方法的主要作用是：
在这个方法里依赖了component这个类，循环调用了这个类的visitTree(visitContext, new RestoreStateCallback());
3)、 // invoke the afterPhase MethodExpression of UIViewRoot
_invokeViewRootAfterPhaseListener(facesContext); ？
如果找不到呢，接着来看这段代码：
String viewId = restoreViewSupport.calculateViewId(facesContext);
// Determine if the current request is an attempt by the
// servlet container to display an error page.
// If the request is an error page request, the servlet container
// is required to set the request parameter "javax.servlet.error.message".
final boolean errorPageRequest = facesContext.getExternalContext().getRequestMap()
.get("javax.servlet.error.message") != null;
// Determine if this request is a postback or an initial request.
// But if it is an error page request, do not treat it as a postback (since 2.0)
if (!errorPageRequest && restoreViewSupport.isPostback(facesContext))
{ // If the request is a postback
if (log.isLoggable(Level.FINEST))
{
log.finest("Request is a postback");
}
try
{
facesContext.setProcessingEvents(false);
// call ViewHandler.restoreView(), passing the FacesContext instance for the current request and the
// view identifier, and returning a UIViewRoot for the restored view.
viewRoot = viewHandler.restoreView(facesContext, viewId);
if (viewRoot == null)
{
// If the return from ViewHandler.restoreView() is null, throw a ViewExpiredException with an
// appropriate error message.
throw new ViewExpiredException("No saved view state could be found for the view identifier: "
+ viewId, viewId);
}
// Store the restored UIViewRoot in the FacesContext.
facesContext.setViewRoot(viewRoot);
}
finally
{
facesContext.setProcessingEvents(true);
}
// Restore binding
// See https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=806
restoreViewSupport.processComponentBinding(facesContext, viewRoot);
}
else
{ // If the request is a non-postback
if (log.isLoggable(Level.FINEST))
{
log.finest("Request is not a postback. New UIViewRoot will be created");
}
//viewHandler.deriveViewId(facesContext, viewId)
//restoreViewSupport.deriveViewId(facesContext, viewId)
ViewDeclarationLanguage vdl = viewHandler.getViewDeclarationLanguage(facesContext,
viewHandler.deriveLogicalViewId(facesContext, viewId));
// viewHandler.deriveLogicalViewId() could trigger an InvalidViewIdException, which
// it is handled internally sending a 404 error code set the response as complete.
if (facesContext.getResponseComplete())
{
return true;
}
if (vdl != null)
{
ViewMetadata metadata = vdl.getViewMetadata(facesContext, viewId);
Collection<UIViewParameter> viewParameters = null;
if (metadata != null)
{
viewRoot = metadata.createMetadataView(facesContext);
if (viewRoot != null)
{
viewParameters = ViewMetadata.getViewParameters(viewRoot);
}
else if(facesContext.getResponseComplete())
{
// this can happen if the current request is a debug request,
// in this case no further processing is necessary
return true;
}
}
// If viewParameters is not an empty collection DO NOT call renderResponse
if ( !(viewParameters != null && !viewParameters.isEmpty()) )
{
// Call renderResponse() on the FacesContext.
facesContext.renderResponse();
}
}
else
{
// Call renderResponse
facesContext.renderResponse();
}
// viewRoot can be null here, if ...
// - we don't have a ViewDeclarationLanguage (e.g. when using facelets-1.x)
// - there is no view metadata or metadata.createMetadataView() returned null
if (viewRoot == null)
{
// call ViewHandler.createView(), passing the FacesContext instance for the current request and
// the view identifier
viewRoot = viewHandler.createView(facesContext, viewId);
}
// Subscribe the newly created UIViewRoot instance to the AfterAddToParent event, passing the
// UIViewRoot instance itself as the listener.
// -= Leonardo Uribe =- This line it is not necessary because it was
// removed from jsf 2.0 section 2.2.1 when pass from EDR2 to Public Review
// viewRoot.subscribeToEvent(PostAddToViewEvent.class, viewRoot);
// Store the new UIViewRoot instance in the FacesContext.
facesContext.setViewRoot(viewRoot);
// Publish an AfterAddToParent event with the created UIViewRoot as the event source.
application.publishEvent(facesContext, PostAddToViewEvent.class, viewRoot);
}
// add the ErrorPageBean to the view map to fully support
// facelet error pages, if we are in ProjectStage Development
// and currently generating an error page
if (errorPageRequest && facesContext.isProjectStage(ProjectStage.Development))
{
facesContext.getViewRoot().getViewMap()
.put(ErrorPageWriter.ERROR_PAGE_BEAN_KEY, new ErrorPageWriter.ErrorPageBean());
}
// invoke the afterPhase MethodExpression of UIViewRoot
_invokeViewRootAfterPhaseListener(facesContext);
return false;
}
1、置ViewId
2、判断是否是个错误页面请求
3、如果这不是一个错误页面请求且是一个回传请求或者初始请求，
那就找出viewRoot并把它设置到facesContext？（viewHandler.restoreView(facesContext, viewId);）
4、如果这不是一个回传请求：
这边依赖于ViewHandler类生成了ViewDeclarationLanguage视图描述语言实例,
如果这个实例不为空，则：用这个实例取得视图元数据
ViewMetadata metadata = vdl.getViewMetadata(facesContext, viewId);
再用视图元数据创建ViewRoot
还用视图元数据取得视图参数viewParameter，如果有直接进入渲染环节
如果这个视图描述语言实例为空，直接进入渲染环节。
如果到这边viewRoot还是为空，则用viewHandler生成视图根目录。
viewRoot = viewHandler.createView(facesContext, viewId);（e.g. when using facelets-1.x）
否则，把viewRoot设置到FacesContext中，
Publish an AfterAddToParent event with the created UIViewRoot as the event source.
// invoke the afterPhase MethodExpression of UIViewRoot
FacesContext可以看做是一个RequestWrapper（注意这个FaceContext和ServletContext不一样，ServletContext是一个Web应用只有一个的全局对象，对应的是一个Web application，而一个FacesContext对应的是一个request，另外，RequestWrapper这个说法不严格，实际上FacesContext里面也包装了ServletContext、Response等）。而LifeCycle可以看做是一个过滤器链（类似于servlet规范里面的Filter Chain）。于是，整个JSF请求处理过程，实际上就是包装成为FaceContext的用户请求，通过类似于一个Filter Chain的LifeCycle的过程。