欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

SpringMVC之RequestContextUtils工具类

程序员文章站 2022-03-02 10:35:00
...

RequestContextUtils类

RequestContextUtils类是Spring提供的用于从HttpServletRequest上下文中获取特殊对象的工具类。该工具类虽然是属于Spring的一部分,但是如果在应用中我们有需要直接获取相关信息的需求,我们也可以直接使用。

从request中获取WebApplicationContext。

RequestContextUtils.getWebApplicationContext(request);

从request中获取LocaleResolver或Locale。

RequestContextUtils.getLocaleResolver(request);
RequestContextUtils.getLocale(request);

从request中获取ThemeResolver或Theme。

RequestContextUtils.getThemeResolver(request);
RequestContextUtils.getTheme(request);

除了上面那些,我们还可以获取FlashMapManager和TimeZone等其它信息。以下是该工具类的完整代码。

public abstract class RequestContextUtils {

	/**
	 * Look for the WebApplicationContext associated with the DispatcherServlet
	 * that has initiated request processing.
	 * @param request current HTTP request
	 * @return the request-specific web application context
	 * @throws IllegalStateException if no servlet-specific context has been found
	 */
	public static WebApplicationContext getWebApplicationContext(ServletRequest request)
		throws IllegalStateException {

		return getWebApplicationContext(request, null);
	}

	/**
	 * 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. This method is useful to
	 * allow components outside the framework, such as JSP tag handlers,
	 * to access the most specific application context available.
	 * @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
	 * @throws IllegalStateException if neither a servlet-specific nor a
	 * global context has been found
	 */
	public static WebApplicationContext getWebApplicationContext(
			ServletRequest request, ServletContext servletContext) throws IllegalStateException {

		WebApplicationContext webApplicationContext = (WebApplicationContext) request.getAttribute(
				DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE);
		if (webApplicationContext == null) {
			if (servletContext == null) {
				throw new IllegalStateException("No WebApplicationContext found: not in a DispatcherServlet request?");
			}
			webApplicationContext = WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);
		}
		return webApplicationContext;
	}

	/**
	 * 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
	 */
	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.
	 * <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.
	 * <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 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()
	 */
	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.
	 * @param request current HTTP request
	 * @return the current ThemeResolver, or {@code null} if not found
	 */
	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.
	 * @param request current HTTP request
	 * @return the current ThemeSource
	 */
	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.
	 * @param request current HTTP request
	 * @return the current theme, or {@code null} if not found
	 * @see #getThemeResolver
	 */
	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 a read-only {@link Map} with "input" flash attributes saved on a
	 * previous request.
	 * @param request the current request
	 * @return a read-only Map, or {@code null} if not found
	 * @see FlashMap
	 */
	@SuppressWarnings("unchecked")
	public static Map<String, ?> getInputFlashMap(HttpServletRequest request) {
		return (Map<String, ?>) request.getAttribute(DispatcherServlet.INPUT_FLASH_MAP_ATTRIBUTE);
	}

	/**
	 * Return the "output" FlashMap with attributes to save for a subsequent request.
	 * @param request the current request
	 * @return a {@link FlashMap} instance (never {@code null} within a DispatcherServlet request)
	 * @see FlashMap
	 */
	public static FlashMap getOutputFlashMap(HttpServletRequest request) {
		return (FlashMap) request.getAttribute(DispatcherServlet.OUTPUT_FLASH_MAP_ATTRIBUTE);
	}

	/**
	 * Return the FlashMapManager instance to save flash attributes with
	 * before a redirect.
	 * @param request the current request
	 * @return a {@link FlashMapManager} instance (never {@code null} within a DispatcherServlet request)
	 */
	public static FlashMapManager getFlashMapManager(HttpServletRequest request) {
		return (FlashMapManager) request.getAttribute(DispatcherServlet.FLASH_MAP_MANAGER_ATTRIBUTE);
	}

}

(本文是基于Spring4.1.0所写)