SpringMVC源码--LocaleResolver

深藏阁楼爱情的钟 2022-05-15 06:37 211阅读 0赞

# LocaleResolver #

public interface LocaleResolver {
        Locale resolveLocale(HttpServletRequest var1);
    
        void setLocale(HttpServletRequest var1, @Nullable HttpServletResponse var2, @Nullable Locale var3);
    }

它的作用是使用request解析出Locale，结构图如下所示：

![70][]

*  AcceptHeaderLocaleResolver直接使用了Header里的“acceptlanguage”的值，不可以在程序中修改；
 *  FixedLocaleResolver用于解析出固定的Locale，也就是说在创建好了就不能修改了；
 *  SessionLocaleResolver用于将Locale保存到Session中；
 *  CookieLocaleResolver用于将Locale保存到Cookie中；

其中在AbstractLocaleContextResolver下的子类添加了对TimeZone时区的支持。

### **1. AcceptHeaderLocaleResolver** ###

public Locale resolveLocale(HttpServletRequest request) {
            Locale defaultLocale = this.getDefaultLocale(); //查找默认的Locale
            if (defaultLocale != null && request.getHeader("Accept-Language") == null) {
                return defaultLocale;
            } else {
                //请求中的Locale
                Locale requestLocale = request.getLocale();
                //获取能支持的Locale
                List<Locale> supportedLocales = this.getSupportedLocales();
                if (!supportedLocales.isEmpty() && !supportedLocales.contains(requestLocale)) {                
                    //两者匹配匹配成功
                    Locale supportedLocale = this.findSupportedLocale(request, supportedLocales);
                    if (supportedLocale != null) {
                        return supportedLocale;
                    } else {
                        return defaultLocale != null ? defaultLocale : requestLocale;
                    }
                } else {
                    return requestLocale;
                }
            }
        }
    
         public void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale) {
            throw new UnsupportedOperationException("Cannot change HTTP accept header - use a different locale resolution strategy");
        }

### 2.FixedLocaleResolver ###

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

### 3.SessionLocaleResolver ###

这个和FixedLocaleResolver的实现差不多，只不过把默认值改成了从Session中获取，如果获取不到还是从默认值谋取，另外这里支持对LocaleContext的修改。

public Locale resolveLocale(HttpServletRequest request) {
            //首先从session中获取
            Locale locale = (Locale)WebUtils.getSessionAttribute(request, this.localeAttributeName);
            if (locale == null) {
                //获取不到获取默认值
                locale = this.determineDefaultLocale(request);
            }
    
            return locale;
        }    
        public LocaleContext resolveLocaleContext(final HttpServletRequest request) {
            return new TimeZoneAwareLocaleContext() {
                public Locale getLocale() {
                    Locale locale = (Locale)WebUtils.getSessionAttribute(request, SessionLocaleResolver.this.localeAttributeName);
                    if (locale == null) {
                        locale = SessionLocaleResolver.this.determineDefaultLocale(request);
                    }
    
                    return locale;
                }
    
                @Nullable
                public TimeZone getTimeZone() {
                    TimeZone timeZone = (TimeZone)WebUtils.getSessionAttribute(request, SessionLocaleResolver.this.timeZoneAttributeName);
                    if (timeZone == null) {
                        timeZone = SessionLocaleResolver.this.determineDefaultTimeZone(request);
                    }
    
                    return timeZone;
                }
            };
        }
    
        public void setLocaleContext(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable 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, this.localeAttributeName, locale);
            WebUtils.setSessionAttribute(request, this.timeZoneAttributeName, timeZone);
        }

###  4.CookieLocaleResolver ###

它和SessionLocaleResolver类似，只是将Session编程Cookie来保存属性了额，只是为了处理Cookie继承了CookieGenerator，所以就没有继承AbstractLocaleContextResolver了，不过任然会提供保存默认的Locale和TimeZone的属性。

[70]: /images/20220515/794b24a0b9a846f3829023e9659d5775.png