springMVC源码分析--动态样式ThemeResolver（一）

本文转自http://blog.csdn.net/qq924862077/ 感谢作者

 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。