springMVC源码分析--国际化LocaleResolver（一）

        springMVC给我们提供了国际化支持，简单来说就是设置整个系统的运行语言，然后根据系统的运行语言来展示对应语言的页面，一般我们称之为多语言。springMVC国际化机制就是可以设置整个系统的运行语言，其定义了一个国际化支持接口LocaleResolver，提供的默认实现类如下图。

springMVC国际化提供了四个默认实现的类AcceptHeaderLocaleResolver，FixedLocaleResolver、CookieLocaleResolver和SessionLocaleResolver。接下来我们简单介绍一下这四个实现类的源码。

AcceptHeaderLocaleResolver：其实没有任何具体实现，是通过浏览器头部的语言信息来进行多语言选择。

public class AcceptHeaderLocaleResolver implements LocaleResolver {@Overridepublic Locale resolveLocale(HttpServletRequest request) {return request.getLocale();}@Overridepublic void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {throw new UnsupportedOperationException("Cannot change HTTP accept header - use a different locale resolution strategy");}}

FixedLocaleResolver：设置固定的语言信息，这样整个系统的语言是一成不变的，用处不大。

public class FixedLocaleResolver extends AbstractLocaleContextResolver {public FixedLocaleResolver() {setDefaultLocale(Locale.getDefault());}public FixedLocaleResolver(Locale locale) {setDefaultLocale(locale);}public FixedLocaleResolver(Locale locale, TimeZone timeZone) {setDefaultLocale(locale);setDefaultTimeZone(timeZone);}@Overridepublic Locale resolveLocale(HttpServletRequest request) {Locale locale = getDefaultLocale();if (locale == null) {locale = Locale.getDefault();}return locale;}@Overridepublic LocaleContext resolveLocaleContext(HttpServletRequest request) {return new TimeZoneAwareLocaleContext() {@Overridepublic Locale getLocale() {return getDefaultLocale();}@Overridepublic TimeZone getTimeZone() {return getDefaultTimeZone();}};}@Overridepublic void setLocaleContext(HttpServletRequest request, HttpServletResponse response, LocaleContext localeContext) {throw new UnsupportedOperationException("Cannot change fixed locale - use a different locale resolution strategy");}}

CookieLocaleResolver：将语言信息设置到Cookie中，这样整个系统就可以获得语言信息

public class CookieLocaleResolver extends CookieGenerator implements LocaleContextResolver {//多语言cookie名称public static final String LOCALE_REQUEST_ATTRIBUTE_NAME = CookieLocaleResolver.class.getName() + ".LOCALE";//多语言时区cookie名称public static final String TIME_ZONE_REQUEST_ATTRIBUTE_NAME = CookieLocaleResolver.class.getName() + ".TIME_ZONE";//默认的多语言cookie名称public static final String DEFAULT_COOKIE_NAME = CookieLocaleResolver.class.getName() + ".LOCALE";private Locale defaultLocale;private TimeZone defaultTimeZone;public CookieLocaleResolver() {setCookieName(DEFAULT_COOKIE_NAME);}public void setDefaultLocale(Locale defaultLocale) {this.defaultLocale = defaultLocale;}protected Locale getDefaultLocale() {return this.defaultLocale;}public void setDefaultTimeZone(TimeZone defaultTimeZone) {this.defaultTimeZone = defaultTimeZone;}protected TimeZone getDefaultTimeZone() {return this.defaultTimeZone;}@Overridepublic Locale resolveLocale(HttpServletRequest request) {parseLocaleCookieIfNecessary(request);return (Locale) request.getAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME);}@Overridepublic LocaleContext resolveLocaleContext(final HttpServletRequest request) {parseLocaleCookieIfNecessary(request);return new TimeZoneAwareLocaleContext() {@Overridepublic Locale getLocale() {return (Locale) request.getAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME);}@Overridepublic TimeZone getTimeZone() {return (TimeZone) request.getAttribute(TIME_ZONE_REQUEST_ATTRIBUTE_NAME);}};}private void parseLocaleCookieIfNecessary(HttpServletRequest request) {if (request.getAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME) == null) {// Retrieve and parse cookie value.Cookie cookie = WebUtils.getCookie(request, getCookieName());Locale locale = null;TimeZone timeZone = null;if (cookie != null) {String value = cookie.getValue();String localePart = value;String timeZonePart = null;int spaceIndex = localePart.indexOf(' ');if (spaceIndex != -1) {localePart = value.substring(0, spaceIndex);timeZonePart = value.substring(spaceIndex + 1);}locale = (!"-".equals(localePart) ? StringUtils.parseLocaleString(localePart) : null);if (timeZonePart != null) {timeZone = StringUtils.parseTimeZoneString(timeZonePart);}if (logger.isDebugEnabled()) {logger.debug("Parsed cookie value [" + cookie.getValue() + "] into locale '" + locale +"'" + (timeZone != null ? " and time zone '" + timeZone.getID() + "'" : ""));}}request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME,(locale != null ? locale: determineDefaultLocale(request)));request.setAttribute(TIME_ZONE_REQUEST_ATTRIBUTE_NAME,(timeZone != null ? timeZone : determineDefaultTimeZone(request)));}}@Overridepublic void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {setLocaleContext(request, response, (locale != null ? new SimpleLocaleContext(locale) : null));}@Overridepublic void setLocaleContext(HttpServletRequest request, HttpServletResponse response, LocaleContext localeContext) {Locale locale = null;TimeZone timeZone = null;if (localeContext != null) {locale = localeContext.getLocale();if (localeContext instanceof TimeZoneAwareLocaleContext) {timeZone = ((TimeZoneAwareLocaleContext) localeContext).getTimeZone();}addCookie(response, (locale != null ? locale : "-") + (timeZone != null ? ' ' + timeZone.getID() : ""));}else {removeCookie(response);}request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME,(locale != null ? locale: determineDefaultLocale(request)));request.setAttribute(TIME_ZONE_REQUEST_ATTRIBUTE_NAME,(timeZone != null ? timeZone : determineDefaultTimeZone(request)));}protected Locale determineDefaultLocale(HttpServletRequest request) {Locale defaultLocale = getDefaultLocale();if (defaultLocale == null) {defaultLocale = request.getLocale();}return defaultLocale;}protected TimeZone determineDefaultTimeZone(HttpServletRequest request) {return getDefaultTimeZone();}}

SessionLocaleResolver：与CookieLocaleResolver类似将语言信息放到Session中，这样整个系统就可以从Session中获得语言信息。

public class SessionLocaleResolver extends AbstractLocaleContextResolver {//语言信息放到session中的名称public static final String LOCALE_SESSION_ATTRIBUTE_NAME = SessionLocaleResolver.class.getName() + ".LOCALE";public static final String TIME_ZONE_SESSION_ATTRIBUTE_NAME = SessionLocaleResolver.class.getName() + ".TIME_ZONE";@Overridepublic Locale resolveLocale(HttpServletRequest request) {Locale locale = (Locale) WebUtils.getSessionAttribute(request, LOCALE_SESSION_ATTRIBUTE_NAME);if (locale == null) {locale = determineDefaultLocale(request);}return locale;}@Overridepublic LocaleContext resolveLocaleContext(final HttpServletRequest request) {return new TimeZoneAwareLocaleContext() {@Overridepublic Locale getLocale() {Locale locale = (Locale) WebUtils.getSessionAttribute(request, LOCALE_SESSION_ATTRIBUTE_NAME);if (locale == null) {locale = determineDefaultLocale(request);}return locale;}@Overridepublic TimeZone getTimeZone() {TimeZone timeZone = (TimeZone) WebUtils.getSessionAttribute(request, TIME_ZONE_SESSION_ATTRIBUTE_NAME);if (timeZone == null) {timeZone = determineDefaultTimeZone(request);}return timeZone;}};}@Overridepublic void setLocaleContext(HttpServletRequest request, HttpServletResponse response, LocaleContext localeContext) {Locale locale = null;TimeZone timeZone = null;if (localeContext != null) {locale = localeContext.getLocale();if (localeContext instanceof TimeZoneAwareLocaleContext) {timeZone = ((TimeZoneAwareLocaleContext) localeContext).getTimeZone();}}WebUtils.setSessionAttribute(request, LOCALE_SESSION_ATTRIBUTE_NAME, locale);WebUtils.setSessionAttribute(request, TIME_ZONE_SESSION_ATTRIBUTE_NAME, timeZone);}protected Locale determineDefaultLocale(HttpServletRequest request) {Locale defaultLocale = getDefaultLocale();if (defaultLocale == null) {defaultLocale = request.getLocale();}return defaultLocale;}protected TimeZone determineDefaultTimeZone(HttpServletRequest request) {return getDefaultTimeZone();}}

通过源码我们可以了解到springMVC对多语言的支持就是设置Locale的语言信息来实现的，只不过是设置了通过cookie、session等方式设置而已，接下来我们会通过demo来进一步介绍这几种实现方式。