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/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.faces.flow;
import java.util.Map;
import jakarta.faces.context.FacesContext;
/**
*
* FlowHandler is the main entry point that enables the runtime to
* interact with the faces flows feature. {@link jakarta.faces.application.NavigationHandler} uses this class when it
* needs to make navigational decisions related to flows. The faces flow feature entirely depends on the
* {@link jakarta.faces.lifecycle.ClientWindow} feature and also on CDI.
*
*
*
*
*
* Defining Flows
*
*
*
* The implementation must support defining faces flows using the <flow-definition> element as
* specified in the Application Configuration Resources XML Schema Definition, or by using the
* {@link jakarta.faces.flow.builder.FlowBuilder} API. Additional means of defining flows may be provided by decorating
* the {@link FlowHandlerFactory}.
*
*
*
* Managing Flows
*
*
*
*
*
* The singleton instance of this class must be thread safe, and therefore must not store any per-user state. Flows are,
* however, traversed in a per-user manner, and must be associated with the current
* {@link jakarta.faces.lifecycle.ClientWindow}. Furthermore, Flows may be nested. These requirements strongly suggest
* managing the flows with a stack-like runtime data structure, stored in a per-user fashion and associated with the
* {@code ClientWindow}. Because Flow instances are immutable, yet the flow stack is
* per-user, implementations must make allowance for flow scoped data (managed beans declared to be {@link FlowScoped}
* and data stored in the Map returned by {@link #getCurrentFlowScope}) to be fully re-entrant. For
* example, consider an application with two flows, A and B, each with a single FlowScoped bean
* MyBeanA and MyBeanB, respectively. Entry into flow A causes MyBeanA to become
* active. Calling from A into B causes MyBeanB to become active. Calling back into A causes a new instance
* of MyBeanA to become active, rather than reactivating the earlier instance of MyBeanA.
*
*
*
*
* The Flow Graph
*
*
*
* Prior versions of the specification defined a flow graph but the only kind of node in the graph was a VDL view. The
* Faces Flow feature currently defines the following node types.
*
*
*
*
* -
*
* View
*
*
*
* This is the regular Jakarta Faces VDL View that has been in the specification since the beginning.
*
*
*
*
* -
*
* Switch
*
*
*
* This is a list of Jakarta Expression Language expressions. When control is passed to a switch node, each expression
* in the list is evaluated and the first one that returns {@code true} is used to define the id of the next node to
* which control must be passed. If none of the expressions evaluates to {@code true}, control passes to the specified
* default id.
*
*
*
*
* -
*
* Return
*
*
*
* This node type specifies an outcome that is returned to the calling flow.
*
*
*
*
* -
*
* Method Call
*
*
*
* This node type allows invocation of arbitrary application logic at any point in the executiong of the flow. An
* outcome can be specified that will cause a navigation case to be navigated to after the method has been invoked.
*
*
*
*
* -
*
* Faces Flow Call
*
*
*
* This node type allows one flow to call another flow. The calling flow remains active and is not exited until control
* returns from the called flow.
*
*
*
*
*
*
*
* Edges in the graph are defined by the existing Jakarta Faces navigation rule system.
*
*
*
* Flows and Model Objects
*
*
*
*
*
* Managed beans annotated with the CDI annotation {@link FlowScoped} are created
* lazily, when referenced, after a user agent's entry into the named scope, and must be made available for
* garbage collection when the user agent leaves the flow.
*
*
*
* The flowScope Jakarta Expression Language implicit object is also available to store values in the
* "current" slope. Values stored in this scope must be made available for garbage collection when the user agent leaves
* the flow.
*
*
*
*
*
*
*
* @since 2.2
*
*/
public abstract class FlowHandler {
/**
*
* Components that are rendered by Renderers of component-family jakarta.faces.OutcomeTarget
* must use this constant as the parameter name for a parameter representing the flow id of the flow that this component
* will cause to be entered.
*
*
* @since 2.2
*/
public static final String FLOW_ID_REQUEST_PARAM_NAME = "jffi";
/**
*
* Components that are rendered by Renderers of component-family jakarta.faces.OutcomeTarget
* must use this constant as the parameter name for a parameter representing the defining document id of the flow that
* this component will cause to be entered.
*
*
* @since 2.2
*/
public static final String TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME = "jftfdi";
/**
*
* Components that are rendered by Renderers of component-family jakarta.faces.OutcomeTarget
* must use this constant as the value of the parameter named by {@link #TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME} when
* returning from a flow (without entering another flow) using such a component.
*
*
* @since 2.2
*/
public static final String NULL_FLOW = "jakarta.faces.flow.NullFlow";
/**
*
* Return the {@code Map} that backs the {@code #{flowScope}} Jakarta Expression Language implicit object or
* {@code null} if no flow is currently active.
*
*
* @return the {@code Map} for this flow scope.
*
* @since 2.2
*/
public abstract Map getCurrentFlowScope();
/**
*
* Return the {@link Flow} whose {@code
* id} is equivalent to the argument {@code id}, within the scope of the argument {@code definingDocument}.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @param definingDocumentId An application unique identifier for the document in which the returned flow is defined.
*
* @param id the id of a {@link Flow}, unique within the scope of the {@code definingDocument}.
*
* @throws NullPointerException if any of the parameters are {@code null}
*
* @return the {@code Flow} for the argument identifiers.
*
* @since 2.2
*/
public abstract Flow getFlow(FacesContext context, String definingDocumentId, String id);
/**
*
* Add the argument {@link Flow} to the collection of {@code Flow}s known to the current application. The implementation
* must be thread safe.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @param toAdd the {@code Flow} to add.
*
* @throws NullPointerException if any of the parameters are {@code null}
*
* @throws IllegalStateException if there is already a flow with the same {@code id} as the argument {@code Flow} within
* the scope of the {@code definingDocument}.
*
* @throws IllegalArgumentException if the {@code id} of the flow to add is {@code null} or the empty string.
*
* @throws IllegalArgumentException if the {@code
* definingDocumentId} of the {@code toAdd} is {@code null}.
*
* @since 2.2
*/
public abstract void addFlow(FacesContext context, Flow toAdd);
/**
*
* Return the currently active {@link Flow} for the argument {@code FacesContext}, or {@code null} if no flow is active.
* A {@code Flow} must always be associated with exactly one {@link jakarta.faces.lifecycle.ClientWindow}, but a
* {@code ClientWindow} may have multiple {@code Flow}s.
*
*
*
*
*
* If {@link #pushReturnMode} had been called with {@code true} as the argument before invoking this method, return the
* preceding flow on the stack instead of the actual current flow, or {@code null} if there is no preceding flow.
* Otherwise, return the current flow.
*
*
*
*
* @param context the {@code FacesContext} for the current request.
*
* @throws NullPointerException if any of the parameters are {@code null}
*
* @return the current {@code Flow} or {@code null} if no flow is active
*
* @since 2.2
*/
public abstract Flow getCurrentFlow(FacesContext context);
/**
*
* Convenience overload that calls {@link FacesContext#getCurrentInstance()} and then calls through to
* {@link #getCurrentFlow(jakarta.faces.context.FacesContext)}.
*
*
* @return the current {@code Flow} or {@code null} if no flow is active
*
* @since 2.2
*/
public Flow getCurrentFlow() {
return getCurrentFlow(FacesContext.getCurrentInstance());
}
/**
*
* Return the last displayed viewId for the current flow, as returned by
* {@link #getCurrentFlow(jakarta.faces.context.FacesContext)}, or {@code null} if there is no current flow.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @throws NullPointerException if {@code context} is {@code null}
*
* @since 2.2
*
* @return the last displayed viewId.
*/
public abstract String getLastDisplayedViewId(FacesContext context);
/**
*
* Enable the correct handling of navigation when processing a return node. The default
* {@link jakarta.faces.application.NavigationHandler} specification requires calling this method before processing the
* navigation rules for the flow return, and calling {@link #popReturnMode}, from a {@code finally} block, immediately
* afterward.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @throws NullPointerException if {@code context} is {@code null}.
*
* @since 2.2
*/
public abstract void pushReturnMode(FacesContext context);
/**
*
* Enable the correct handling of navigation when processing a return node. The default
* {@link jakarta.faces.application.NavigationHandler} specification requires calling this method from a {@code finally}
* block, immediately attempting to process the navigation rules in the context of a flow return.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @throws NullPointerException if {@code context} is {@code null}.
*
* @since 2.2
*/
public abstract void popReturnMode(FacesContext context);
/**
*
* Perform a transition in the flow graph for the current user's {@link jakarta.faces.lifecycle.ClientWindow}. Obtain
* references to the {@code Flow} instances corresponding to the {@code origin} and {@code destination} arguments. If
* the {@code origin Flow} is equal to the {@code destination Flow}, take no action and return {@code null}. Otherwise,
* if the {@code outboundCallNode} argument is non-{@code null} save aside the outbound parameters. For discussion
* evaluatedParams is a data structure that stores the evaluated values of any outbound parameters. It
* is necessary to evaluate these values before popping any flow scopes because the values may refer to scoped instances
* that need to be passed to the target flow, but will not be available once the new scope is activated. Save aside the
* outbound parameters using the following algorithm.
*
*
*
*
*
*
*
* If the {@code outboundParameters} property of {@code
* outboundCallNode} is non-{@code null} and not empty, and the {@code inboundParameters} property of the target flow is
* non-{@code null} and not empty, for each entry in the outbound parameters whose name matches an entry in the inbound
* parameters, evaluate the value of the parameter, and put the evaluated value into evaluatedParams
* under the corresponding name. Otherwise, consider evaluatedParams to be empty.
*
*
*
*
*
* If the {@code destination Flow} is a sub-flow of the {@code
* origin Flow} push the {@code destination Flow} onto the flow data structure and return {@code the destination Flow}.
* Otherwise, pop the current {@code Flow} from the flow data structure. If the {@code destination Flow} is
* non-{@code null}, make the {@code
* destination Flow} the current flow, pushing it onto the data structure. If evaluatedParams is not
* empty, for each entry, find the corresponding parameter in the target flow's inbound parameters and call its
* {@code setValue} method, passing the value from evaluatedParams.
*
*
*
*
* @param context the {@code FacesContext} for the current request.
*
* @param sourceFlow the current {@code Flow}, or {@code null} if there is no source flow.
*
* @param targetFlow the destination {@code Flow}, or {@code null} if there is no destination flow.
*
* @param outboundCallNode the flow call node causing this transition, or {@code null} if this transition is not caused
* by a flow call.
*
* @param toViewId the viewId of the view being displayed as a result of this transition. This parameter makes it
* possible to implement {@link #getLastDisplayedViewId}.
*
* @throws NullPointerException if {@code context} or {@code toViewId} is {@code null}.
*
*
* @since 2.2
*/
public abstract void transition(FacesContext context, Flow sourceFlow, Flow targetFlow, FlowCallNode outboundCallNode, String toViewId);
/**
*
* Allow for flow transitions in the case of components rendered by the renderers from component-family
* jakarta.faces.OutcomeTarget. These transitions must happen at the front of the request processing
* lifecycle due to the HTTP GET based nature of such components. Therefore, this method is called from the restore view
* phase of the lifecycle.
*
*
*
*
*
* Let flowId be the value in the request parameter map for the parameter whose name is given by the value of
* {@link #FLOW_ID_REQUEST_PARAM_NAME}. Let toFlowDocumentId be the value in the request parameter map for the
* paramater whose name is given by the value of {@link #TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME}. If
* toFlowDocumentId is null, take no action and return. Otherwise, let sourceFlow be the
* return from {@link #getCurrentFlow(jakarta.faces.context.FacesContext)}. A null value indicates there is
* no current flow, which will be the case if this navigation is trying to enter a flow. If flowId is not
* null and toFlowDocumentId is not equal to the value of {@link #NULL_FLOW}, let
* targetFlow be the result of calling
* {@link #getFlow(jakarta.faces.context.FacesContext, java.lang.String, java.lang.String)}, passing
* toFlowDocumentId and flowId as the last two arguments, respectively. If the result is
* non-null, let flowCallNode be the return from calling {@link Flow#getFlowCall} on the
* sourceFlow, passing targetFlow as the argument. Otherwise, targetFlow and
* flowCallNode must remain null, indicating that this is a flow return. Call
* {@link FacesContext#getViewRoot()} and let toViewId be the the return from calling
* {@link jakarta.faces.component.UIViewRoot#getViewId} on it.
*
*
*
* Call, {@link #transition}, passing the arguments gathered in the preceding algorithm.
*
*
*
*
* @since 2.2
*
* @param context the {@code FacesContext} for the current request.
*
* @throws NullPointerException if {@code context} is {@code null}.
*/
public abstract void clientWindowTransition(FacesContext context);
/**
*
* Return {@code true} if and only if the flow referenced by the argument {@code definingDocument} and {@code id} is
* currently active.
*
*
* @param context the {@code FacesContext} for the current request.
*
* @param definingDocument An application unique identifier for the document in which the returned flow is defined.
*
* @param id the id of a {@link Flow}, unique within the scope of the {@code definingDocument}.
*
* @throws NullPointerException if any of the parameters are {@code null}
*
* @return true if and only if the referenced flow is active
*
* @since 2.2
*/
public abstract boolean isActive(FacesContext context, String definingDocument, String id);
}