/*
 * Copyright 2002-2015 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.web.portlet.multipart;

import javax.portlet.ActionRequest;

import org.springframework.web.multipart.MultipartException;

/**
 * Portlet version of Spring's multipart resolution strategy for file uploads
 * as defined in <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC 1867</a>.
 *
 * <p>Implementations are typically usable both within any application context
 * and standalone.
 *
 * <p>There is one concrete implementation included in Spring:
 * <ul>
 * <li>{@link org.springframework.web.multipart.commons.CommonsMultipartResolver}
 * for Apache Commons FileUpload
 * </ul>
 *
 * <p>There is no default resolver implementation used for Spring
 * {@link org.springframework.web.portlet.DispatcherPortlet DispatcherPortlets},
 * as an application might choose to parse its multipart requests itself. To
 * define an implementation, create a bean with the id "portletMultipartResolver"
 * in a {@code DispatcherPortlet's} application context. Such a resolver
 * gets applied to all requests handled by that {@code DispatcherPortlet}.
 *
 * <p>If a {@code DispatcherPortlet} detects a multipart request, it will
 * resolve it via the configured
 * {@link org.springframework.web.portlet.multipart.PortletMultipartResolver}
 * and pass on a wrapped Portlet {@link ActionRequest}. Controllers can then
 * cast their given request to the {@link MultipartActionRequest} interface,
 * being able to access {@code MultipartFiles}. Note that this cast is only
 * supported in case of an actual multipart request.
 *
 * <pre class="code"> public void handleActionRequest(ActionRequest request, ActionResponse response) {
 *   MultipartActionRequest multipartRequest = (MultipartActionRequest) request;
 *   MultipartFile multipartFile = multipartRequest.getFile("image");
 *   ...
 * }</pre>
 *
 * Instead of direct access, command or form controllers can register a
 * {@link org.springframework.web.multipart.support.ByteArrayMultipartFileEditor}
 * or {@link org.springframework.web.multipart.support.StringMultipartFileEditor}
 * with their data binder, to automatically apply multipart content to form
 * bean properties.
 *
 * <p>Note: There is hardly ever a need to access the {@code MultipartResolver}
 * itself from application code. It will simply do its work behind the scenes,
 * making {@code MultipartActionRequests} available to controllers.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see MultipartActionRequest
 * @see org.springframework.web.multipart.MultipartFile
 * @see CommonsPortletMultipartResolver
 * @see org.springframework.web.multipart.support.ByteArrayMultipartFileEditor
 * @see org.springframework.web.multipart.support.StringMultipartFileEditor
 * @see org.springframework.web.portlet.DispatcherPortlet
 */
public interface PortletMultipartResolver {

	/**
	 * Determine if the given request contains multipart content.
	 * <p>Will typically check for content type
	 * "{@code multipart/form-data}", but the actually accepted requests
	 * might depend on the capabilities of the resolver implementation.
	 * @param request the portlet request to be evaluated
	 * @return whether the request contains multipart content
	 */
	boolean isMultipart(ActionRequest request);

	/**
	 * Parse the given portlet request into multipart files and parameters,
	 * and wrap the request inside a MultipartActionRequest object
	 * that provides access to file descriptors and makes contained
	 * parameters accessible via the standard PortletRequest methods.
	 * @param request the portlet request to wrap (must be of a multipart content type)
	 * @return the wrapped portlet request
	 * @throws org.springframework.web.multipart.MultipartException if the portlet request
	 * is not multipart, or if implementation-specific problems are encountered
	 * (such as exceeding file size limits)
	 * @see org.springframework.web.portlet.multipart.MultipartActionRequest#getFile
	 * @see org.springframework.web.portlet.multipart.MultipartActionRequest#getFileNames
	 * @see org.springframework.web.portlet.multipart.MultipartActionRequest#getFileMap
	 * @see javax.portlet.ActionRequest#getParameter
	 * @see javax.portlet.ActionRequest#getParameterNames
	 * @see javax.portlet.ActionRequest#getParameterMap
	 */
	MultipartActionRequest resolveMultipart(ActionRequest request) throws MultipartException;

	/**
	 * Cleanup any resources used for the multipart handling,
	 * such as storage for any uploaded file(s).
	 * @param request the request to cleanup resources for
	 */
	void cleanupMultipart(MultipartActionRequest request);

}
