org.springframework.webflow.execution.repository.continuation.FlowExecutionContinuationGroup Maven / Gradle / Ivy
/*
* Copyright 2002-2006 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.execution.repository.continuation;
import java.io.Serializable;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
/**
* A group of flow execution continuations. Simple typed data structure backed
* by a map and linked list. Supports expelling the oldest continuation once a
* maximum group size is met.
*
* @author Keith Donald
*/
class FlowExecutionContinuationGroup implements Serializable {
/**
* A map of continuations; the key is the continuation id, and the value is
* the {@link FlowExecutionContinuation} object.
*/
private Map continuations = new HashMap();
/**
* An ordered list of continuation ids. Each continuation id represents an
* pointer to a continuation in the map. The first element is the oldest
* continuation and the last is the youngest.
*/
private LinkedList continuationIds = new LinkedList();
/**
* The maximum number of continuations allowed in this group.
*/
private int maxContinuations = -1;
/**
* Creates a new flow execution continuation group.
* @param maxContinuations the maximum number of continuations that can be
* stored in this group, -1 for unlimited
*/
public FlowExecutionContinuationGroup(int maxContinuations) {
this.maxContinuations = maxContinuations;
}
/**
* Returns the count of continuations in this group.
*/
public int getContinuationCount() {
return continuationIds.size();
}
/**
* Returns the continuation with the provided id, or
* null if no such continuation exists with that id.
* @param id the continuation id
* @return the continuation
* @throws ContinuationNotFoundException if the id does not match a
* continuation in this group
*/
public FlowExecutionContinuation get(Serializable id) throws ContinuationNotFoundException {
FlowExecutionContinuation continuation = (FlowExecutionContinuation)continuations.get(id);
if (continuation == null) {
throw new ContinuationNotFoundException(id);
}
return continuation;
}
/**
* Add a flow execution continuation with given id to this group.
* @param continuationId the continuation id
* @param continuation the continuation
*/
public void add(Serializable continuationId, FlowExecutionContinuation continuation) {
continuations.put(continuationId, continuation);
continuationIds.add(continuationId);
// remove the oldest continuation if them maximium number of
// continuations has been exceeded
if (maxExceeded()) {
removeOldestContinuation();
}
}
/**
* Has the maximum number of allowed continuations in this group been exceeded?
*/
private boolean maxExceeded() {
return maxContinuations > 0 && continuationIds.size() > maxContinuations;
}
/**
* Remove the olders continuation from this group.
*/
private void removeOldestContinuation() {
continuations.remove(continuationIds.removeFirst());
}
}