springMVC原始碼分析--國際化LocaleResolver（一）
阿新 • • 發佈：2018-12-31
springMVC給我們提供了國際化支援，簡單來說就是設定整個系統的執行語言，然後根據系統的執行語言來展示對應語言的頁面，一般我們稱之為多語言。springMVC國際化機制就是可以設定整個系統的執行語言，其定義了一個國際化支援介面LocaleResolver，提供的預設實現類如下圖。
springMVC國際化提供了四個預設實現的類AcceptHeaderLocaleResolver，FixedLocaleResolver、CookieLocaleResolver和SessionLocaleResolver。接下來我們簡單介紹一下這四個實現類的原始碼。
AcceptHeaderLocaleResolver：其實沒有任何具體實現，是通過瀏覽器頭部的語言資訊來進行多語言選擇。
FixedLocaleResolver：設定固定的語言資訊，這樣整個系統的語言是一成不變的，用處不大。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"); } }
CookieLocaleResolver：將語言資訊設定到Cookie中，這樣整個系統就可以獲得語言資訊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"); } }
public class CookieLocaleResolver extends CookieGenerator implements LocaleContextResolver {
//多語言cookie名稱
public static final String LOCALE_REQUEST_ATTRIBUTE_NAME = CookieLocaleResolver.class.getName() + ".LOCALE";
//多語言時區cookie名稱
public static final String TIME_ZONE_REQUEST_ATTRIBUTE_NAME = CookieLocaleResolver.class.getName() + ".TIME_ZONE";
//預設的多語言cookie名稱
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();
}
}public class SessionLocaleResolver extends AbstractLocaleContextResolver {
//語言資訊放到session中的名稱
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();
}
}通過原始碼我們可以瞭解到springMVC對多語言的支援就是設定Locale的語言資訊來實現的，只不過是設定了通過cookie、session等方式設定而已，接下來我們會通過demo來進一步介紹這幾種實現方式。