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/*
 * Copyright 2002-2018 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.server;

import java.security.Principal;
import java.time.Instant;
import java.util.Map;
import java.util.function.Consumer;
import java.util.function.Function;

import reactor.core.publisher.Mono;

import org.springframework.context.ApplicationContext;
import org.springframework.context.i18n.LocaleContext;
import org.springframework.http.codec.multipart.Part;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MultiValueMap;

/**
 * Contract for an HTTP request-response interaction. Provides access to the HTTP
 * request and response and also exposes additional server-side processing
 * related properties and features such as request attributes.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public interface ServerWebExchange {

	/**
	 * Name of {@link #getAttributes() attribute} whose value can be used to
	 * correlate log messages for this exchange. Use {@link #getLogPrefix()} to
	 * obtain a consistently formatted prefix based on this attribute.
	 * @since 5.1
	 * @see #getLogPrefix()
	 */
	String LOG_ID_ATTRIBUTE = ServerWebExchange.class.getName() + ".LOG_ID";


	/**
	 * Return the current HTTP request.
	 */
	ServerHttpRequest getRequest();

	/**
	 * Return the current HTTP response.
	 */
	ServerHttpResponse getResponse();

	/**
	 * Return a mutable map of request attributes for the current exchange.
	 */
	Map getAttributes();

	/**
	 * Return the request attribute value if present.
	 * @param name the attribute name
	 * @param  the attribute type
	 * @return the attribute value
	 */
	@SuppressWarnings("unchecked")
	@Nullable
	default  T getAttribute(String name) {
		return (T) getAttributes().get(name);
	}

	/**
	 * Return the request attribute value or if not present raise an
	 * {@link IllegalArgumentException}.
	 * @param name the attribute name
	 * @param  the attribute type
	 * @return the attribute value
	 */
	@SuppressWarnings("unchecked")
	default  T getRequiredAttribute(String name) {
		T value = getAttribute(name);
		Assert.notNull(value, () -> "Required attribute '" + name + "' is missing");
		return value;
	}

	/**
	 * Return the request attribute value, or a default, fallback value.
	 * @param name the attribute name
	 * @param defaultValue a default value to return instead
	 * @param  the attribute type
	 * @return the attribute value
	 */
	@SuppressWarnings("unchecked")
	default  T getAttributeOrDefault(String name, T defaultValue) {
		return (T) getAttributes().getOrDefault(name, defaultValue);
	}

	/**
	 * Return the web session for the current request. Always guaranteed  to
	 * return an instance either matching to the session id requested by the
	 * client, or with a new session id either because the client did not
	 * specify one or because the underlying session had expired. Use of this
	 * method does not automatically create a session. See {@link WebSession}
	 * for more details.
	 */
	Mono getSession();

	/**
	 * Return the authenticated user for the request, if any.
	 */
	 Mono getPrincipal();

	/**
	 * Return the form data from the body of the request if the Content-Type is
	 * {@code "application/x-www-form-urlencoded"} or an empty map otherwise.
	 * 

Note: calling this method causes the request body to * be read and parsed in full and the resulting {@code MultiValueMap} is * cached so that this method is safe to call more than once. */ Mono> getFormData(); /** * Return the parts of a multipart request if the Content-Type is * {@code "multipart/form-data"} or an empty map otherwise. *

Note: calling this method causes the request body to * be read and parsed in full and the resulting {@code MultiValueMap} is * cached so that this method is safe to call more than once. */ Mono> getMultipartData(); /** * Return the {@link LocaleContext} using the configured * {@link org.springframework.web.server.i18n.LocaleContextResolver}. */ LocaleContext getLocaleContext(); /** * Return the {@link ApplicationContext} associated with the web application, * if it was initialized with one via * {@link org.springframework.web.server.adapter.WebHttpHandlerBuilder#applicationContext(ApplicationContext)}. * @since 5.0.3 * @see org.springframework.web.server.adapter.WebHttpHandlerBuilder#applicationContext(ApplicationContext) */ @Nullable ApplicationContext getApplicationContext(); /** * Returns {@code true} if the one of the {@code checkNotModified} methods * in this contract were used and they returned true. */ boolean isNotModified(); /** * An overloaded variant of {@link #checkNotModified(String, Instant)} with * a last-modified timestamp only. * @param lastModified the last-modified time * @return whether the request qualifies as not modified */ boolean checkNotModified(Instant lastModified); /** * An overloaded variant of {@link #checkNotModified(String, Instant)} with * an {@code ETag} (entity tag) value only. * @param etag the entity tag for the underlying resource. * @return true if the request does not require further processing. */ boolean checkNotModified(String etag); /** * Check whether the requested resource has been modified given the supplied * {@code ETag} (entity tag) and last-modified timestamp as determined by * the application. Also transparently prepares the response, setting HTTP * status, and adding "ETag" and "Last-Modified" headers when applicable. * This method works with conditional GET/HEAD requests as well as with * conditional POST/PUT/DELETE requests. *

Note: The HTTP specification recommends setting both * ETag and Last-Modified values, but you can also use * {@code #checkNotModified(String)} or * {@link #checkNotModified(Instant)}. * @param etag the entity tag that the application determined for the * underlying resource. This parameter will be padded with quotes (") * if necessary. * @param lastModified the last-modified timestamp that the application * determined for the underlying resource * @return true if the request does not require further processing. */ boolean checkNotModified(@Nullable String etag, Instant lastModified); /** * Transform the given url according to the registered transformation function(s). * By default, this method returns the given {@code url}, though additional * transformation functions can by registered with {@link #addUrlTransformer} * @param url the URL to transform * @return the transformed URL */ String transformUrl(String url); /** * Register an additional URL transformation function for use with {@link #transformUrl}. * The given function can be used to insert an id for authentication, a nonce for CSRF * protection, etc. *

Note that the given function is applied after any previously registered functions. * @param transformer a URL transformation function to add */ void addUrlTransformer(Function transformer); /** * Return a log message prefix to use to correlate messages for this exchange. * The prefix is based on the value of the attribute {@link #LOG_ID_ATTRIBUTE} * along with some extra formatting so that the prefix can be conveniently * prepended with no further formatting no separators required. * @return the log message prefix or an empty String if the * {@link #LOG_ID_ATTRIBUTE} is not set. * @since 5.1 */ String getLogPrefix(); /** * Return a builder to mutate properties of this exchange by wrapping it * with {@link ServerWebExchangeDecorator} and returning either mutated * values or delegating back to this instance. */ default Builder mutate() { return new DefaultServerWebExchangeBuilder(this); } /** * Builder for mutating an existing {@link ServerWebExchange}. * Removes the need */ interface Builder { /** * Configure a consumer to modify the current request using a builder. *

Effectively this: *

		 * exchange.mutate().request(builder-> builder.method(HttpMethod.PUT));
		 *
		 * // vs...
		 *
		 * ServerHttpRequest request = exchange.getRequest().mutate()
		 *     .method(HttpMethod.PUT)
		 *     .build();
		 *
		 * exchange.mutate().request(request);
		 * 
* @see ServerHttpRequest#mutate() */ Builder request(Consumer requestBuilderConsumer); /** * Set the request to use especially when there is a need to override * {@link ServerHttpRequest} methods. To simply mutate request properties * see {@link #request(Consumer)} instead. * @see org.springframework.http.server.reactive.ServerHttpRequestDecorator */ Builder request(ServerHttpRequest request); /** * Set the response to use. * @see org.springframework.http.server.reactive.ServerHttpResponseDecorator */ Builder response(ServerHttpResponse response); /** * Set the {@code Mono} to return for this exchange. */ Builder principal(Mono principalMono); /** * Build a {@link ServerWebExchange} decorator with the mutated properties. */ ServerWebExchange build(); } }




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