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package javax.faces.flow;
import java.util.Map;
import javax.faces.context.FacesContext;
/**
* FlowHandler is the main entry
* point that enables the runtime to interact with the faces flows
* feature. {@link javax.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
* javax.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 javax.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 javax.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 JSF VDL View that has been in the
* specification since the beginning.
* Switch
* This is a list of EL 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 JSF 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 EL 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 javax.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 javax.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 javax.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 = "javax.faces.flow.NullFlow";
/**
* Return the {@code Map} that backs
* the {@code #{flowScope}} EL 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 javax.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(javax.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(javax.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 javax.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 javax.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
* javax.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 javax.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(javax.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(javax.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 javax.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);
}