State.java
/*
* Copyright 2004-2012 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
*
* https://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.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.style.ToStringCreator;
import org.springframework.util.Assert;
import org.springframework.webflow.core.AnnotatedObject;
import org.springframework.webflow.definition.FlowDefinition;
import org.springframework.webflow.definition.StateDefinition;
import org.springframework.webflow.execution.FlowExecutionException;
/**
* A point in a flow where something happens. What happens is determined by a state's type. Standard types of states
* include action states, view states, subflow states, and end states.
* <p>
* Each state is associated with exactly one owning flow definition. Specializations of this class capture all the
* configuration information needed for a specific kind of state.
* <p>
* Subclasses should implement the <code>doEnter</code> method to execute the processing that should occur when this
* state is entered, acting on its configuration information. The ability to plug-in custom state types that execute
* different behaviors is the classic GoF state pattern.
* <p>
* Equality: Two states are equal if they have the same id and are part of the same flow.
*
* @see org.springframework.webflow.engine.TransitionableState
* @see org.springframework.webflow.engine.ActionState
* @see org.springframework.webflow.engine.ViewState
* @see org.springframework.webflow.engine.SubflowState
* @see org.springframework.webflow.engine.EndState
* @see org.springframework.webflow.engine.DecisionState
*
* @author Keith Donald
* @author Erwin Vervaet
*/
public abstract class State extends AnnotatedObject implements StateDefinition {
/**
* Logger, for use in subclasses.
*/
protected final Log logger = LogFactory.getLog(getClass());
/**
* The state's owning flow.
*/
private Flow flow;
/**
* The state identifier, unique to the owning flow.
*/
private String id;
/**
* The list of actions to invoke when this state is entered.
*/
private ActionList entryActionList = new ActionList();
/**
* The set of exception handlers for this state.
*/
private FlowExecutionExceptionHandlerSet exceptionHandlerSet = new FlowExecutionExceptionHandlerSet();
/**
* Creates a state for the provided <code>flow</code> identified by the provided <code>id</code>. The id must be
* locally unique to the owning flow. The state will be automatically added to the flow.
* @param flow the owning flow
* @param id the state identifier (must be unique to the flow)
* @throws IllegalArgumentException if this state cannot be added to the flow, for instance when the provided id is
* not unique in the owning flow
* @see #getEntryActionList()
* @see #getExceptionHandlerSet()
*/
protected State(Flow flow, String id) throws IllegalArgumentException {
setId(id);
setFlow(flow);
}
// implementing StateDefinition
public FlowDefinition getOwner() {
return flow;
}
public String getId() {
return id;
}
public boolean isViewState() {
return false;
}
// implementation specific
/**
* Returns the owning flow.
*/
public Flow getFlow() {
return flow;
}
/**
* Set the owning flow.
* @throws IllegalArgumentException if this state cannot be added to the flow
*/
private void setFlow(Flow flow) throws IllegalArgumentException {
Assert.hasText(getId(), "The id of the state should be set before adding the state to a flow");
Assert.notNull(flow, "The owning flow is required");
this.flow = flow;
flow.add(this);
}
/**
* Set the state identifier, unique to the owning flow.
* @param id the state identifier
*/
private void setId(String id) {
Assert.hasText(id, "This state must have a valid identifier");
this.id = id;
}
/**
* Returns the list of actions executed by this state when it is entered. The returned list is mutable.
* @return the state entry action list
*/
public ActionList getEntryActionList() {
return entryActionList;
}
/**
* Returns a mutable set of exception handlers, allowing manipulation of how exceptions are handled when thrown
* within this state.
* <p>
* Exception handlers are invoked when an exception occurs when this state is entered, and can execute custom
* exception handling logic as well as select an error view to display.
* @return the state exception handler set
*/
public FlowExecutionExceptionHandlerSet getExceptionHandlerSet() {
return exceptionHandlerSet;
}
/**
* Returns a flag indicating if this state is the start state of its owning flow.
* @return true if the flow is the start state, false otherwise
*/
public boolean isStartState() {
return flow.getStartState() == this;
}
// id and flow based equality
public boolean equals(Object o) {
if (!(o instanceof State)) {
return false;
}
State other = (State) o;
return id.equals(other.id) && flow.equals(other.flow);
}
public int hashCode() {
return id.hashCode() + flow.hashCode();
}
// behavioral methods
/**
* Enter this state in the provided flow control context. This implementation just calls the
* {@link #doEnter(RequestControlContext)} hook method, which should be implemented by subclasses, after executing
* the entry actions.
* @param context the control context for the currently executing flow, used by this state to manipulate the flow
* execution
* @throws FlowExecutionException if an exception occurs in this state
*/
public final void enter(RequestControlContext context) throws FlowExecutionException {
if (logger.isDebugEnabled()) {
logger.debug("Entering state '" + getId() + "' of flow '" + getFlow().getId() + "'");
}
context.setCurrentState(this);
doPreEntryActions(context);
entryActionList.execute(context);
doEnter(context);
}
/**
* Hook method to execute before running state entry actions upon state entry. Does nothing by default. Subclasses
* may override.
* @param context the request control context
* @throws FlowExecutionException if an exception occurs
*/
protected void doPreEntryActions(RequestControlContext context) throws FlowExecutionException {
}
/**
* Hook method to execute custom behavior as a result of entering this state. By implementing this method subclasses
* specialize the behavior of the state.
* @param context the control context for the currently executing flow, used by this state to manipulate the flow
* execution
* @throws FlowExecutionException if an exception occurs in this state
*/
protected abstract void doEnter(RequestControlContext context) throws FlowExecutionException;
/**
* Handle an exception that occurred in this state during the context of the current flow execution request.
* @param exception the exception that occurred
* @param context the flow execution control context
*/
public boolean handleException(FlowExecutionException exception, RequestControlContext context) {
return getExceptionHandlerSet().handleException(exception, context);
}
public String toString() {
ToStringCreator creator = new ToStringCreator(this).append("id", getId()).append("flow", flow.getId())
.append("entryActionList", entryActionList).append("exceptionHandlerSet", exceptionHandlerSet);
appendToString(creator);
return creator.toString();
}
/**
* Subclasses may override this hook method to print their internal state to a string. This default implementation
* does nothing.
* @param creator the toString creator, to print properties to string
* @see #toString()
*/
protected void appendToString(ToStringCreator creator) {
}
}