https://github.com/spring-projects/spring-framework: Spring Web MVC (Spring IO)
  • Juergen Hoeller 
/*
 * 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.servlet.support;

import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.i18n.LocaleContext;
import org.springframework.context.i18n.TimeZoneAwareLocaleContext;
import org.springframework.lang.Nullable;
import org.springframework.ui.context.Theme;
import org.springframework.ui.context.ThemeSource;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.FlashMap;
import org.springframework.web.servlet.FlashMapManager;
import org.springframework.web.servlet.LocaleContextResolver;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.ThemeResolver;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;


Utility class for easy access to request-specific state which has been set by the DispatcherServlet. 
Supports lookup of current WebApplicationContext, LocaleResolver,
Locale, ThemeResolver, Theme, and MultipartResolver.

Author:Juergen Hoeller, Rossen Stoyanchev
See Also:
Since:03.03.2003
/**
 * Utility class for easy access to request-specific state which has been
 * set by the {@link org.springframework.web.servlet.DispatcherServlet}.
 *
 * <p>Supports lookup of current WebApplicationContext, LocaleResolver,
 * Locale, ThemeResolver, Theme, and MultipartResolver.
 *
 * @author Juergen Hoeller
 * @author Rossen Stoyanchev
 * @since 03.03.2003
 * @see RequestContext
 * @see org.springframework.web.servlet.DispatcherServlet
 */
public abstract class RequestContextUtils {

	
The name of the bean to use to look up in an implementation of RequestDataValueProcessor has been configured. 
Since:4.2.1
/**
	 * The name of the bean to use to look up in an implementation of
	 * {@link RequestDataValueProcessor} has been configured.
	 * @since 4.2.1
	 */
	public static final String REQUEST_DATA_VALUE_PROCESSOR_BEAN_NAME = "requestDataValueProcessor";


	
Look for the WebApplicationContext associated with the DispatcherServlet
that has initiated request processing, and for the global context if none
was found associated with the current request. The global context will
be found via the ServletContext or via ContextLoader's current context.

NOTE: This variant remains compatible with Servlet 2.5, explicitly
checking a given ServletContext instead of deriving it from the request.

Params:
  • request – current HTTP request
  • servletContext – current servlet context
See Also:
Returns:the request-specific WebApplicationContext, or the global one if no request-specific context has been found, or null if none
Since:4.2.1
/**
	 * Look for the WebApplicationContext associated with the DispatcherServlet
	 * that has initiated request processing, and for the global context if none
	 * was found associated with the current request. The global context will
	 * be found via the ServletContext or via ContextLoader's current context.
	 * <p>NOTE: This variant remains compatible with Servlet 2.5, explicitly
	 * checking a given ServletContext instead of deriving it from the request.
	 * @param request current HTTP request
	 * @param servletContext current servlet context
	 * @return the request-specific WebApplicationContext, or the global one
	 * if no request-specific context has been found, or {@code null} if none
	 * @since 4.2.1
	 * @see DispatcherServlet#WEB_APPLICATION_CONTEXT_ATTRIBUTE
	 * @see WebApplicationContextUtils#getWebApplicationContext(ServletContext)
	 * @see ContextLoader#getCurrentWebApplicationContext()
	 */
	@Nullable
	public static WebApplicationContext findWebApplicationContext(
			HttpServletRequest request, @Nullable ServletContext servletContext) {

		WebApplicationContext webApplicationContext = (WebApplicationContext) request.getAttribute(
				DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE);
		if (webApplicationContext == null) {
			if (servletContext != null) {
				webApplicationContext = WebApplicationContextUtils.getWebApplicationContext(servletContext);
			}
			if (webApplicationContext == null) {
				webApplicationContext = ContextLoader.getCurrentWebApplicationContext();
			}
		}
		return webApplicationContext;
	}

	
Look for the WebApplicationContext associated with the DispatcherServlet
that has initiated request processing, and for the global context if none
was found associated with the current request. The global context will
be found via the ServletContext or via ContextLoader's current context.

NOTE: This variant requires Servlet 3.0+ and is generally recommended
for forward-looking custom user code.

Params:
  • request – current HTTP request
See Also:
Returns:the request-specific WebApplicationContext, or the global one if no request-specific context has been found, or null if none
Since:4.2.1
/**
	 * Look for the WebApplicationContext associated with the DispatcherServlet
	 * that has initiated request processing, and for the global context if none
	 * was found associated with the current request. The global context will
	 * be found via the ServletContext or via ContextLoader's current context.
	 * <p>NOTE: This variant requires Servlet 3.0+ and is generally recommended
	 * for forward-looking custom user code.
	 * @param request current HTTP request
	 * @return the request-specific WebApplicationContext, or the global one
	 * if no request-specific context has been found, or {@code null} if none
	 * @since 4.2.1
	 * @see #findWebApplicationContext(HttpServletRequest, ServletContext)
	 * @see ServletRequest#getServletContext()
	 * @see ContextLoader#getCurrentWebApplicationContext()
	 */
	@Nullable
	public static WebApplicationContext findWebApplicationContext(HttpServletRequest request) {
		return findWebApplicationContext(request, request.getServletContext());
	}

	
Return the LocaleResolver that has been bound to the request by the
DispatcherServlet.

Params:
  • request – current HTTP request
Returns:the current LocaleResolver, or null if not found
/**
	 * Return the LocaleResolver that has been bound to the request by the
	 * DispatcherServlet.
	 * @param request current HTTP request
	 * @return the current LocaleResolver, or {@code null} if not found
	 */
	@Nullable
	public static LocaleResolver getLocaleResolver(HttpServletRequest request) {
		return (LocaleResolver) request.getAttribute(DispatcherServlet.LOCALE_RESOLVER_ATTRIBUTE);
	}

	
Retrieve the current locale from the given request, using the
LocaleResolver bound to the request by the DispatcherServlet
(if available), falling back to the request's accept-header Locale.

This method serves as a straightforward alternative to the standard Servlet getLocale.getLocale() method, falling back to the latter if no more specific locale has been found. 
Consider using LocaleContextHolder.getLocale() which will normally be populated with the same Locale. 
Params:
  • request – current HTTP request
See Also:
Returns:the current locale for the given request, either from the
LocaleResolver or from the plain request itself
/**
	 * Retrieve the current locale from the given request, using the
	 * LocaleResolver bound to the request by the DispatcherServlet
	 * (if available), falling back to the request's accept-header Locale.
	 * <p>This method serves as a straightforward alternative to the standard
	 * Servlet {@link javax.servlet.http.HttpServletRequest#getLocale()} method,
	 * falling back to the latter if no more specific locale has been found.
	 * <p>Consider using {@link org.springframework.context.i18n.LocaleContextHolder#getLocale()}
	 * which will normally be populated with the same Locale.
	 * @param request current HTTP request
	 * @return the current locale for the given request, either from the
	 * LocaleResolver or from the plain request itself
	 * @see #getLocaleResolver
	 * @see org.springframework.context.i18n.LocaleContextHolder#getLocale()
	 */
	public static Locale getLocale(HttpServletRequest request) {
		LocaleResolver localeResolver = getLocaleResolver(request);
		return (localeResolver != null ? localeResolver.resolveLocale(request) : request.getLocale());
	}

	
Retrieve the current time zone from the given request, using the
TimeZoneAwareLocaleResolver bound to the request by the DispatcherServlet
(if available), falling back to the system's default time zone.

Note: This method returns null if no specific time zone can be resolved for the given request. This is in contrast to getLocale where there is always the request's accept-header locale to fall back to. 
Consider using LocaleContextHolder.getTimeZone() which will normally be populated with the same TimeZone: That method only differs in terms of its fallback to the system time zone if the LocaleResolver hasn't provided a specific time zone (instead of this method's null). 
Params:
  • request – current HTTP request
See Also:
Returns:the current time zone for the given request, either from the TimeZoneAwareLocaleResolver or null if none associated
/**
	 * Retrieve the current time zone from the given request, using the
	 * TimeZoneAwareLocaleResolver bound to the request by the DispatcherServlet
	 * (if available), falling back to the system's default time zone.
	 * <p>Note: This method returns {@code null} if no specific time zone can be
	 * resolved for the given request. This is in contrast to {@link #getLocale}
	 * where there is always the request's accept-header locale to fall back to.
	 * <p>Consider using {@link org.springframework.context.i18n.LocaleContextHolder#getTimeZone()}
	 * which will normally be populated with the same TimeZone: That method only
	 * differs in terms of its fallback to the system time zone if the LocaleResolver
	 * hasn't provided a specific time zone (instead of this method's {@code null}).
	 * @param request current HTTP request
	 * @return the current time zone for the given request, either from the
	 * TimeZoneAwareLocaleResolver or {@code null} if none associated
	 * @see #getLocaleResolver
	 * @see org.springframework.context.i18n.LocaleContextHolder#getTimeZone()
	 */
	@Nullable
	public static TimeZone getTimeZone(HttpServletRequest request) {
		LocaleResolver localeResolver = getLocaleResolver(request);
		if (localeResolver instanceof LocaleContextResolver) {
			LocaleContext localeContext = ((LocaleContextResolver) localeResolver).resolveLocaleContext(request);
			if (localeContext instanceof TimeZoneAwareLocaleContext) {
				return ((TimeZoneAwareLocaleContext) localeContext).getTimeZone();
			}
		}
		return null;
	}

	
Return the ThemeResolver that has been bound to the request by the
DispatcherServlet.

Params:
  • request – current HTTP request
Returns:the current ThemeResolver, or null if not found
/**
	 * Return the ThemeResolver that has been bound to the request by the
	 * DispatcherServlet.
	 * @param request current HTTP request
	 * @return the current ThemeResolver, or {@code null} if not found
	 */
	@Nullable
	public static ThemeResolver getThemeResolver(HttpServletRequest request) {
		return (ThemeResolver) request.getAttribute(DispatcherServlet.THEME_RESOLVER_ATTRIBUTE);
	}

	
Return the ThemeSource that has been bound to the request by the
DispatcherServlet.

Params:
  • request – current HTTP request
Returns:the current ThemeSource
/**
	 * Return the ThemeSource that has been bound to the request by the
	 * DispatcherServlet.
	 * @param request current HTTP request
	 * @return the current ThemeSource
	 */
	@Nullable
	public static ThemeSource getThemeSource(HttpServletRequest request) {
		return (ThemeSource) request.getAttribute(DispatcherServlet.THEME_SOURCE_ATTRIBUTE);
	}

	
Retrieves the current theme from the given request, using the ThemeResolver
and ThemeSource bound to the request by the DispatcherServlet.

Params:
  • request – current HTTP request
See Also:
  • getThemeResolver
Returns:the current theme, or null if not found
/**
	 * Retrieves the current theme from the given request, using the ThemeResolver
	 * and ThemeSource bound to the request by the DispatcherServlet.
	 * @param request current HTTP request
	 * @return the current theme, or {@code null} if not found
	 * @see #getThemeResolver
	 */
	@Nullable
	public static Theme getTheme(HttpServletRequest request) {
		ThemeResolver themeResolver = getThemeResolver(request);
		ThemeSource themeSource = getThemeSource(request);
		if (themeResolver != null && themeSource != null) {
			String themeName = themeResolver.resolveThemeName(request);
			return themeSource.getTheme(themeName);
		}
		else {
			return null;
		}
	}

	
Return read-only "input" flash attributes from request before redirect.

Params:
  • request – current request
See Also:
Returns:a read-only Map, or null if not found
/**
	 * Return read-only "input" flash attributes from request before redirect.
	 * @param request current request
	 * @return a read-only Map, or {@code null} if not found
	 * @see FlashMap
	 */
	@SuppressWarnings("unchecked")
	@Nullable
	public static Map<String, ?> getInputFlashMap(HttpServletRequest request) {
		return (Map<String, ?>) request.getAttribute(DispatcherServlet.INPUT_FLASH_MAP_ATTRIBUTE);
	}

	
Return "output" FlashMap to save attributes for request after redirect.

Params:
  • request – current request
Returns:a FlashMap instance, never null within a DispatcherServlet-handled request
/**
	 * Return "output" FlashMap to save attributes for request after redirect.
	 * @param request current request
	 * @return a {@link FlashMap} instance, never {@code null} within a
	 * {@code DispatcherServlet}-handled request
	 */
	public static FlashMap getOutputFlashMap(HttpServletRequest request) {
		return (FlashMap) request.getAttribute(DispatcherServlet.OUTPUT_FLASH_MAP_ATTRIBUTE);
	}

	
Return the FlashMapManager instance to save flash attributes. 
As of 5.0 the convenience method saveOutputFlashMap may be used to save the "output" FlashMap. 
Params:
  • request – the current request
Returns:a FlashMapManager instance, never null within a DispatcherServlet-handled request
/**
	 * Return the {@code FlashMapManager} instance to save flash attributes.
	 * <p>As of 5.0 the convenience method {@link #saveOutputFlashMap} may be
	 * used to save the "output" FlashMap.
	 * @param request the current request
	 * @return a {@link FlashMapManager} instance, never {@code null} within a
	 * {@code DispatcherServlet}-handled request
	 */
	@Nullable
	public static FlashMapManager getFlashMapManager(HttpServletRequest request) {
		return (FlashMapManager) request.getAttribute(DispatcherServlet.FLASH_MAP_MANAGER_ATTRIBUTE);
	}

	
Convenience method that retrieves the "output"
FlashMap, updates it with the path and query params of the target URL, and then saves it using the FlashMapManager. 
Params:
  • location – the target URL for the redirect
  • request – the current request
  • response – the current response
Since:5.0
/**
	 * Convenience method that retrieves the {@link #getOutputFlashMap "output"
	 * FlashMap}, updates it with the path and query params of the target URL,
	 * and then saves it using the {@link #getFlashMapManager FlashMapManager}.
	 * @param location the target URL for the redirect
	 * @param request the current request
	 * @param response the current response
	 * @since 5.0
	 */
	public static void saveOutputFlashMap(String location, HttpServletRequest request, HttpServletResponse response) {
		FlashMap flashMap = getOutputFlashMap(request);
		if (CollectionUtils.isEmpty(flashMap)) {
			return;
		}

		UriComponents uriComponents = UriComponentsBuilder.fromUriString(location).build();
		flashMap.setTargetRequestPath(uriComponents.getPath());
		flashMap.addTargetRequestParams(uriComponents.getQueryParams());

		FlashMapManager manager = getFlashMapManager(request);
		Assert.state(manager != null, "No FlashMapManager. Is this a DispatcherServlet handled request?");
		manager.saveOutputFlashMap(flashMap, request, response);
	}

}