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 { @Override public Locale resolveLocale(HttpServletRequest request) { return request.getLocale(); } @Override public 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); } @Override public Locale resolveLocale(HttpServletRequest request) { Locale locale = getDefaultLocale(); if (locale == null) { locale = Locale.getDefault(); } return locale; } @Override public LocaleContext resolveLocaleContext(HttpServletRequest request) { return new TimeZoneAwareLocaleContext() { @Override public Locale getLocale() { return getDefaultLocale(); } @Override public TimeZone getTimeZone() { return getDefaultTimeZone(); } }; } @Override public 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; } @Override public Locale resolveLocale(HttpServletRequest request) { parseLocaleCookieIfNecessary(request); return (Locale) request.getAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME); } @Override public LocaleContext resolveLocaleContext(final HttpServletRequest request) { parseLocaleCookieIfNecessary(request); return new TimeZoneAwareLocaleContext() { @Override public Locale getLocale() { return (Locale) request.getAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME); } @Override public 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))); } } @Override public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) { setLocaleContext(request, response, (locale != null ? new SimpleLocaleContext(locale) : null)); } @Override public 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"; @Override public Locale resolveLocale(HttpServletRequest request) { Locale locale = (Locale) WebUtils.getSessionAttribute(request, LOCALE_SESSION_ATTRIBUTE_NAME); if (locale == null) { locale = determineDefaultLocale(request); } return locale; } @Override public LocaleContext resolveLocaleContext(final HttpServletRequest request) { return new TimeZoneAwareLocaleContext() { @Override public Locale getLocale() { Locale locale = (Locale) WebUtils.getSessionAttribute(request, LOCALE_SESSION_ATTRIBUTE_NAME); if (locale == null) { locale = determineDefaultLocale(request); } return locale; } @Override public TimeZone getTimeZone() { TimeZone timeZone = (TimeZone) WebUtils.getSessionAttribute(request, TIME_ZONE_SESSION_ATTRIBUTE_NAME); if (timeZone == null) { timeZone = determineDefaultTimeZone(request); } return timeZone; } }; } @Override public 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。