org.springframework.webflow.engine.SubflowState Maven / Gradle / Ivy
/*
* Copyright 2004-2007 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.webflow.engine;
import org.springframework.core.style.ToStringCreator;
import org.springframework.util.Assert;
import org.springframework.webflow.core.collection.AttributeMap;
import org.springframework.webflow.core.collection.MutableAttributeMap;
import org.springframework.webflow.execution.FlowExecutionException;
import org.springframework.webflow.execution.RequestContext;
import org.springframework.webflow.execution.ViewSelection;
/**
* A transitionable state that spawns a subflow when executed. When the subflow
* this state spawns ends, the ending result is used as grounds for a state
* transition out of this state.
*
* A subflow state may be configured to map input data from its flow -- acting
* as the parent flow -- down to the subflow when the subflow is spawned. In
* addition, output data produced by the subflow may be mapped up to the parent
* flow when the subflow ends and the parent flow resumes. See the
* {@link FlowAttributeMapper} interface definition for more information on how
* to do this. The logic for ending a subflow is located in the {@link EndState}
* implementation.
*
* @see org.springframework.webflow.engine.FlowAttributeMapper
* @see org.springframework.webflow.engine.EndState
*
* @author Keith Donald
* @author Erwin Vervaet
*/
public class SubflowState extends TransitionableState {
/**
* The subflow that should be spawned when this subflow state is entered.
*/
private Flow subflow;
/**
* The attribute mapper that should map attributes from the parent flow down
* to the spawned subflow and visa versa.
*/
private FlowAttributeMapper attributeMapper;
/**
* Create a new subflow state.
* @param flow the owning flow
* @param id the state identifier (must be unique to the flow)
* @param subflow the subflow to spawn
* @throws IllegalArgumentException when this state cannot be added to given
* flow, e.g. because the id is not unique
* @see #setAttributeMapper(FlowAttributeMapper)
*/
public SubflowState(Flow flow, String id, Flow subflow) throws IllegalArgumentException {
super(flow, id);
setSubflow(subflow);
}
/**
* Returns the subflow spawned by this state.
*/
public Flow getSubflow() {
return subflow;
}
/**
* Set the subflow that will be spawned by this state.
* @param subflow the subflow to spawn
*/
private void setSubflow(Flow subflow) {
Assert.notNull(subflow, "A subflow state must have a subflow; the subflow is required");
this.subflow = subflow;
}
/**
* Returns the attribute mapper used to map data between the parent and child
* flow, or null if no mapping is needed.
*/
public FlowAttributeMapper getAttributeMapper() {
return attributeMapper;
}
/**
* Set the attribute mapper used to map model data between the parent and
* child flow. Can be null if no mapping is needed.
*/
public void setAttributeMapper(FlowAttributeMapper attributeMapper) {
this.attributeMapper = attributeMapper;
}
/**
* Specialization of State's doEnter template method that
* executes behaviour specific to this state type in polymorphic fashion.
*
* Entering this state, creates the subflow input map and spawns the subflow
* in the current flow execution.
* @param context the control context for the currently executing flow, used
* by this state to manipulate the flow execution
* @return a view selection containing model and view information needed to
* render the results of the state execution
* @throws FlowExecutionException if an exception occurs in this state
*/
protected ViewSelection doEnter(RequestControlContext context) throws FlowExecutionException {
if (logger.isDebugEnabled()) {
logger.debug("Spawning subflow '" + getSubflow().getId() + "' within flow '" + getFlow().getId() + "'");
}
return context.start(getSubflow(), createSubflowInput(context));
}
/**
* Create the input data map for the spawned subflow session. The returned
* map will be passed to {@link Flow#start(RequestControlContext, MutableAttributeMap)}.
*/
protected MutableAttributeMap createSubflowInput(RequestContext context) {
if (getAttributeMapper() != null) {
if (logger.isDebugEnabled()) {
logger.debug("Messaging the configured attribute mapper to map attributes "
+ "down to the spawned subflow for access within the subflow");
}
return getAttributeMapper().createFlowInput(context);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("No attribute mapper configured for this subflow state '" + getId()
+ "' -- As a result, no attributes will be passed to the spawned subflow '"
+ subflow.getId() + "'");
}
return null;
}
}
/**
* Called on completion of the subflow to handle the subflow result event as
* determined by the end state reached by the subflow.
*/
public ViewSelection onEvent(RequestControlContext context) {
mapSubflowOutput(context.getLastEvent().getAttributes(), context);
return super.onEvent(context);
}
/**
* Map the output data produced by the subflow back into the request context
* (typically flow scope).
*/
private void mapSubflowOutput(AttributeMap subflowOutput, RequestContext context) {
if (getAttributeMapper() != null) {
if (logger.isDebugEnabled()) {
logger.debug("Messaging the configured attribute mapper to map subflow result attributes to the "
+ "resuming parent flow -- It will have access to attributes passed up by the completed subflow");
}
attributeMapper.mapFlowOutput(subflowOutput, context);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("No attribute mapper is configured for the resuming subflow state '" + getId()
+ "' -- As a result, no attributes of the ending flow will be passed to the resuming parent flow");
}
}
}
protected void appendToString(ToStringCreator creator) {
creator.append("subflow", subflow.getId()).append("attributeMapper", attributeMapper);
super.appendToString(creator);
}
}