org.springframework.webflow.context.ExternalContextHolder 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.context;
import org.springframework.util.Assert;
/**
* Simple holder class that associates an {@link ExternalContext} instance with the current thread. The ExternalContext
* will not be inherited by any child threads spawned by the current thread.
*
* Used as a central holder for the current ExternalContext in Spring Web Flow, wherever necessary. Often used by
* artifacts needing access to the current application session.
*
* @see ExternalContext
*
* @author Keith Donald
*/
public final class ExternalContextHolder {
private static final ThreadLocal externalContextHolder = new ThreadLocal();
/**
* Associate the given ExternalContext with the current thread.
* @param externalContext the current ExternalContext, or null to reset the thread-bound context
*/
public static void setExternalContext(ExternalContext externalContext) {
externalContextHolder.set(externalContext);
}
/**
* Return the ExternalContext associated with the current thread, if any.
* @return the current ExternalContext
* @throws IllegalStateException if no ExternalContext is bound to this thread
*/
public static ExternalContext getExternalContext() {
Assert.state(externalContextHolder.get() != null, "No external context is bound to this thread");
return (ExternalContext) externalContextHolder.get();
}
// not instantiable
private ExternalContextHolder() {
}
}