001/*
002 * Copyright 2002-2017 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.context.request.async;
018
019import javax.servlet.ServletRequest;
020import javax.servlet.http.HttpServletRequest;
021import javax.servlet.http.HttpServletResponse;
022
023import org.springframework.util.ClassUtils;
024import org.springframework.web.context.request.RequestAttributes;
025import org.springframework.web.context.request.WebRequest;
026
027/**
028 * Utility methods related to processing asynchronous web requests.
029 *
030 * @author Rossen Stoyanchev
031 * @author Juergen Hoeller
032 * @since 3.2
033 */
034public abstract class WebAsyncUtils {
035
036        public static final String WEB_ASYNC_MANAGER_ATTRIBUTE = WebAsyncManager.class.getName() + ".WEB_ASYNC_MANAGER";
037
038        // Determine whether Servlet 3.0's ServletRequest.startAsync method is available
039        private static final boolean startAsyncAvailable = ClassUtils.hasMethod(ServletRequest.class, "startAsync");
040
041
042        /**
043         * Obtain the {@link WebAsyncManager} for the current request, or if not
044         * found, create and associate it with the request.
045         */
046        public static WebAsyncManager getAsyncManager(ServletRequest servletRequest) {
047                WebAsyncManager asyncManager = null;
048                Object asyncManagerAttr = servletRequest.getAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE);
049                if (asyncManagerAttr instanceof WebAsyncManager) {
050                        asyncManager = (WebAsyncManager) asyncManagerAttr;
051                }
052                if (asyncManager == null) {
053                        asyncManager = new WebAsyncManager();
054                        servletRequest.setAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, asyncManager);
055                }
056                return asyncManager;
057        }
058
059        /**
060         * Obtain the {@link WebAsyncManager} for the current request, or if not
061         * found, create and associate it with the request.
062         */
063        public static WebAsyncManager getAsyncManager(WebRequest webRequest) {
064                int scope = RequestAttributes.SCOPE_REQUEST;
065                WebAsyncManager asyncManager = null;
066                Object asyncManagerAttr = webRequest.getAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, scope);
067                if (asyncManagerAttr instanceof WebAsyncManager) {
068                        asyncManager = (WebAsyncManager) asyncManagerAttr;
069                }
070                if (asyncManager == null) {
071                        asyncManager = new WebAsyncManager();
072                        webRequest.setAttribute(WEB_ASYNC_MANAGER_ATTRIBUTE, asyncManager, scope);
073                }
074                return asyncManager;
075        }
076
077        /**
078         * Create an AsyncWebRequest instance. By default, an instance of
079         * {@link StandardServletAsyncWebRequest} gets created when running in
080         * Servlet 3.0 (or higher) environment - as a fallback, an instance
081         * of {@link NoSupportAsyncWebRequest} will be returned.
082         * @param request the current request
083         * @param response the current response
084         * @return an AsyncWebRequest instance (never {@code null})
085         */
086        public static AsyncWebRequest createAsyncWebRequest(HttpServletRequest request, HttpServletResponse response) {
087                return (startAsyncAvailable ? AsyncWebRequestFactory.createStandardAsyncWebRequest(request, response) :
088                                new NoSupportAsyncWebRequest(request, response));
089        }
090
091
092        /**
093         * Inner class to avoid a hard dependency on the Servlet 3.0 API.
094         */
095        private static class AsyncWebRequestFactory {
096
097                public static AsyncWebRequest createStandardAsyncWebRequest(HttpServletRequest request, HttpServletResponse response) {
098                        return new StandardServletAsyncWebRequest(request, response);
099                }
100        }
101
102}