/* * Copyright 2002-2017 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.web.context.request;import org.springframework.beans.factory.ObjectFactory;import org.springframework.beans.factory.config.Scope;import org.springframework.lang.Nullable;/** * Abstract {@link Scope} implementation that reads from a particular scope * in the current thread-bound {@link RequestAttributes} object. * * <p>Subclasses simply need to implement {@link #getScope()} to instruct * this class which {@link RequestAttributes} scope to read attributes from. * * <p>Subclasses may wish to override the {@link #get} and {@link #remove} * methods to add synchronization around the call back into this super class. * * @author Rod Johnson * @author Juergen Hoeller * @author Rob Harrop * @since 2.0 */public abstract class AbstractRequestAttributesScope implements Scope { @Override public Object get(String name, ObjectFactory<?> objectFactory) { RequestAttributes attributes = RequestContextHolder.currentRequestAttributes(); Object scopedObject = attributes.getAttribute(name, getScope()); if (scopedObject == null) { scopedObject = objectFactory.getObject(); attributes.setAttribute(name, scopedObject, getScope()); // Retrieve object again, registering it for implicit session attribute updates. // As a bonus, we also allow for potential decoration at the getAttribute level. Object retrievedObject = attributes.getAttribute(name, getScope()); if (retrievedObject != null) { // Only proceed with retrieved object if still present (the expected case). // If it disappeared concurrently, we return our locally created instance. scopedObject = retrievedObject; } } return scopedObject; } @Override @Nullable public Object remove(String name) { RequestAttributes attributes = RequestContextHolder.currentRequestAttributes(); Object scopedObject = attributes.getAttribute(name, getScope()); if (scopedObject != null) { attributes.removeAttribute(name, getScope()); return scopedObject; } else { return null; }