LocaleResolver
LocaleResolver 是一个解决国际化的策略接口。它包含两个方法：
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| public interface LocaleResolver {
Locale resolveLocale(HttpServletRequest request);
void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale);
}
|
类图
SpringMVC 默认使用的是：AcceptHeaderLocaleResolver 。
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| /**
* LocaleResolver 接口的实现类
* 简单地使用 HTTP 请求头里的 Accept-Language 来指定 Locale对象(即客户端浏览器发送的语言环境，通常是客户端的操作系统)
*
* 注意:不支持 setLocale 方法，因为只能通过更改客户端的区域设置来更改 Accept-Language 请求头
*/
public class AcceptHeaderLocaleResolver implements LocaleResolver {
private final List<Locale> supportedLocales = new ArrayList<>(4);
@Nullable
private Locale defaultLocale;
/**
* 配置支持的区域设置列表
*/
public void setSupportedLocales(@Nullable List<Locale> locales) {
this.supportedLocales.clear();
if (locales != null) {
this.supportedLocales.addAll(locales);
}
}
/**
* 返回配置的支持的区域设置列表
*/
public List<Locale> getSupportedLocales() {
return this.supportedLocales;
}
/**
* 如果 HTTP 请求头没有 Accept-Language，则使用该默认的语言环境设置
*/
public void setDefaultLocale(@Nullable Locale defaultLocale) {
this.defaultLocale = defaultLocale;
}
/**
* 返回默认配置的语言环境(如果有)
*/
@Nullable
public Locale getDefaultLocale() {
return this.defaultLocale;
}
@Override
public Locale resolveLocale(HttpServletRequest request) {
Locale defaultLocale = getDefaultLocale();
if (defaultLocale != null && request.getHeader("Accept-Language") == null) {
return defaultLocale;
}
Locale requestLocale = request.getLocale();
if (isSupportedLocale(requestLocale)) {
return requestLocale;
}
Locale supportedLocale = findSupportedLocale(request);
if (supportedLocale != null) {
return supportedLocale;
}
return (defaultLocale != null ? defaultLocale : requestLocale);
}
private boolean isSupportedLocale(Locale locale) {
List<Locale> supportedLocales = getSupportedLocales();
return (supportedLocales.isEmpty() || supportedLocales.contains(locale));
}
@Nullable
private Locale findSupportedLocale(HttpServletRequest request) {
Enumeration<Locale> requestLocales = request.getLocales();
while (requestLocales.hasMoreElements()) {
Locale locale = requestLocales.nextElement();
if (getSupportedLocales().contains(locale)) {
return locale;
}
}
return null;
}
@Override
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");
}
}
|
处理流程
- 如果 HTTP 请求头里不含有 Accept-Language ，并且默认的语言环境 defaultLocale 不为空，则使用默认的语言环境。否则，从请求里获得 Locale 。
- 而一般的我们没有配置 supportedLocales 与defaultLocale 属性(需要配置注入)，所以 AcceptHeaderLocaleResolver 使用Accept-Language 来构造 Locale 对象。
AbstractLocaleResolver
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| /**
* 实现 LocaleResolver 接口的抽象基类
* 提供对默认语言环境的支持
*/
public abstract class AbstractLocaleResolver implements LocaleResolver {
@Nullable
private Locale defaultLocale;
public void setDefaultLocale(@Nullable Locale defaultLocale) {
this.defaultLocale = defaultLocale;
}
@Nullable
protected Locale getDefaultLocale() {
return this.defaultLocale;
}
}
|
LocaleContextResolver
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| public interface LocaleContextResolver extends LocaleResolver {
LocaleContext resolveLocaleContext(HttpServletRequest request);
void setLocaleContext(HttpServletRequest request, @Nullable HttpServletResponse response,
@Nullable LocaleContext localeContext);
}
|
AbstractLocaleContextResolver
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| /**
* LocaleContextResolver 实现的抽象基类:提供对默认语言环境和默认时区的支持
* 还提供了 resolveLocale 和 setLocale 的预实现版本，委托给 resolveLocaleContext 和 setLocaleContext
*/
public abstract class AbstractLocaleContextResolver extends AbstractLocaleResolver implements LocaleContextResolver {
@Nullable
private TimeZone defaultTimeZone;
public void setDefaultTimeZone(@Nullable TimeZone defaultTimeZone) {
this.defaultTimeZone = defaultTimeZone;
}
@Nullable
public TimeZone getDefaultTimeZone() {
return this.defaultTimeZone;
}
@Override
public Locale resolveLocale(HttpServletRequest request) {
Locale locale = resolveLocaleContext(request).getLocale();
return (locale != null ? locale : request.getLocale());
}
@Override
public void setLocale(HttpServletRequest request, @Nullable HttpServletResponse response, @Nullable Locale locale) {
setLocaleContext(request, response, (locale != null ? new SimpleLocaleContext(locale) : null));
}
}
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SessionLocaleResolver
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| public class SessionLocaleResolver extends AbstractLocaleContextResolver {
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";
private String localeAttributeName = LOCALE_SESSION_ATTRIBUTE_NAME;
private String timeZoneAttributeName = TIME_ZONE_SESSION_ATTRIBUTE_NAME;
/**
* 在 HttpSession 中指定相应属性的名称，保存当前的 Locale 值
* 默认值为 LOCALE_SESSION_ATTRIBUTE_NAME
*/
public void setLocaleAttributeName(String localeAttributeName) {
this.localeAttributeName = localeAttributeName;
}
/**
* 在 HttpSession 中指定相应属性的名称，保存当前的 TimeZone 值
* 默认值为 TIME_ZONE_SESSION_ATTRIBUTE_NAME
*/
public void setTimeZoneAttributeName(String timeZoneAttributeName) {
this.timeZoneAttributeName = timeZoneAttributeName;
}
@Override
public Locale resolveLocale(HttpServletRequest request) {
Locale locale = (Locale) WebUtils.getSessionAttribute(request, this.localeAttributeName);
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, localeAttributeName);
if (locale == null) {
locale = determineDefaultLocale(request);
}
return locale;
}
@Override
@Nullable
public TimeZone getTimeZone() {
TimeZone timeZone = (TimeZone) WebUtils.getSessionAttribute(request, timeZoneAttributeName);
if (timeZone == null) {
timeZone = determineDefaultTimeZone(request);
}
return timeZone;
}
};
}
@Override
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();
}
}
// 将 Locale 与 TimeZone 保存到 HttpSession
WebUtils.setSessionAttribute(request, this.localeAttributeName, locale);
WebUtils.setSessionAttribute(request, this.timeZoneAttributeName, timeZone);
}
/**
* 确定给定请求的默认语言环境，如果没有找到 Locale 会话属性，则调用
* 默认实现返回指定的默认语言环境（如果有的话）返回到请求的Accept-Header 语言环境
*/
protected Locale determineDefaultLocale(HttpServletRequest request) {
Locale defaultLocale = getDefaultLocale();
if (defaultLocale == null) {
defaultLocale = request.getLocale();
}
return defaultLocale;
}
/**
* 确定给定请求的默认时区，如果未找到TimeZone会话属性，则调用
* 默认实现返回指定的默认时区（如果有），否则返回null
*/
@Nullable
protected TimeZone determineDefaultTimeZone(HttpServletRequest request) {
return getDefaultTimeZone();
}
}
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