标签:return springboot locale request bundle 源码 null 服务端 String
序言:
目前大多数公司都使用前后端分离的架构来搭建自己的web服务器。
这个程序是解决,当后端出现错误,由后端控制发送到前端的程序。
实现方式
@Component
public class I18NUtls {
private static MessageSource messageSource;
@Autowired
public void setMessageSource(MessageSource messageSource) {
I18NUtls.messageSource = messageSource;
}
public static String getMessage(String name) {
HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();
String lan = request.getHeader("Accept-Language");
if(lan == null) {
lan = "zh_CN";
}
return messageSource.getMessage(name, null, new Locale(lan));
}
}
spring配置
spring.messages.basename=i18n/messages
messages.properties
test=\u6D4B\u8BD5
test.properties
test=test
测试的action
package com.aming.test;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.ServletRequestAttributes;
@RestController
public class I18NTestAction {
@RequestMapping("testI18N")
public String testI18N() {
return I18NUtls.getMessage("test");
}
}
源码解读
一.关于HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();线程安全问题。
首先在前端发送请求时,会经过。
1.FramewokeServlet: processRequest
//请求发来的时候
//获取 RequestAttributes
RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
//新建requestAttributes
ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());
//初始化ContextHolders
initContextHolders(request, localeContext, requestAttributes);
在FramewokeServlet: processRequest 方法中调用了 buildRequestAttributes方法,而我们获取request就是从这个里面获取的。
2. FramewokeServlet: buildRequestAttributes 新建requestAttributes
//返回了一个ServletRequestAttributes
return new ServletRequestAttributes(request, response);
new了一个ServletRequestAttributes
3. ServletRequestAttributes
//返回的ServletRequestAttributes简单的保存了,request和response
public ServletRequestAttributes(HttpServletRequest request, HttpServletResponse response) {
this(request);
this.response = response;
}
public ServletRequestAttributes(HttpServletRequest request) {
Assert.notNull(request, "Request must not be null");
this.request = request;
}
在ServletRequestAttributes将request保存
4. FramewokeServlet:initContextHolders
//将requestAttributes放入了RequestContextHolder
if (requestAttributes != null) {
RequestContextHolder.setRequestAttributes(requestAttributes, this.threadContextInheritable);
}
然后将requestAttributes放入RequestContextHolder中
5. RequestContextHolder:setRequestAttributes
//将requestAttributes 放入了 requestAttributesHolder 而
// private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
new NamedThreadLocal<RequestAttributes>("Request attributes");
public static void setRequestAttributes(RequestAttributes attributes, boolean inheritable) {
if (attributes == null) {
resetRequestAttributes();
}
else {
if (inheritable) {
inheritableRequestAttributesHolder.set(attributes);
requestAttributesHolder.remove();
}
else {
requestAttributesHolder.set(attributes);
inheritableRequestAttributesHolder.remove();
}
}
}
使用requestAttributesHolder存储attributes 而attributes中由request
requestAttributesHolder是ThreadLocal对象。可以保证当我们在多线程环境下从RequestContextHolder获取attributes的时候,不会引发线程问题。
6:RequestContextHolder:getRequestAttributes
//从ThreadLocal中取出当前线程的request
public static RequestAttributes getRequestAttributes() {
RequestAttributes attributes = requestAttributesHolder.get();
if (attributes == null) {
attributes = inheritableRequestAttributesHolder.get();
}
return attributes;
}
总结,在FramewokeServlet的processRequest放置了当前线程的request在RequestContextHolder的requestAttributesHolder中,以为requestAttributesHolder为TheadLocal,ThreadLocal是根据当前线程获取值,所以是线程安全。
二. 关于 MeesageSource国际化获取code对应的国际化值的过程
从AbstractMessageSource:getMessage开始看
1.AbstractMessageSource:getMessage
public final String getMessage(String code, Object[] args, Locale locale) throws NoSuchMessageException {
//获取国际化信息
String msg = getMessageInternal(code, args, locale);
if (msg != null) {
return msg;
}
//没有获取到,获取默认的信息
String fallback = getDefaultMessage(code);
if (fallback != null) {
return fallback;
}
throw new NoSuchMessageException(code, locale);
}
调用AbstractMessageSource:getMessageInternal获取国际化信息
2. AbstractMessageSource:getMessageInternal
//调用resolveCodeWithoutArguments去获取国际化信息
if (code == null) {
return null;
}
if (locale == null) {
locale = Locale.getDefault();
}
Object[] argsToUse = args;
if (!isAlwaysUseMessageFormat() && ObjectUtils.isEmpty(args)) {
//没有参数就
String message = resolveCodeWithoutArguments(code, locale);
if (message != null) {
return message;
}
}
最后放回的是 resolveCodeWithoutArguments
3. AbstractMessageSource:resolveCodeWithoutArguments
//先获取spring中配置的basename
//然后根据getResourceBundle获取bundle
//然后根据code 获取对应的国际化信息
protected String resolveCodeWithoutArguments(String code, Locale locale) {
Set<String> basenames = getBasenameSet();
for (String basename : basenames) {
ResourceBundle bundle = getResourceBundle(basename, locale);
if (bundle != null) {
String result = getStringOrNull(bundle, code);
if (result != null) {
return result;
}
}
}
return null;
}
调用了ResourceBundleMessageSource:getStringOrNul
4.getStringOrNul:ResourceBundleMessageSource
return bundle.getString(key);
5. ResourceBundle:getString
return (String) getObject(key);
- ResourceBundle :getObject
Object obj = handleGetObject(key);
- PropertyResourceBundle:handleGetObject
private Map<String,Object> lookup;
return lookup.get(key);
最后使用的是lookup.loopup是一个 hashMap
总结:MessageSource是内部村粗了一个hashmap来存储键值对,
然后通过hashMap.get获取。
三. 关于PropertyResourceBundle中lookup的初始化
1.实例化hashMap
public PropertyResourceBundle (Reader reader) throws IOException {
Properties properties = new Properties();
properties.load(reader);
lookup = new HashMap(properties);
}
2.Properties.load:load0
String key = loadConvert(lr.lineBuf, 0, keyLen, convtBuf);
String value = loadConvert(lr.lineBuf, valueStart, limit - valueStart, convtBuf);
put(key, value);
Properties 是根据hastable实现的。
总结:
在ResourceBundleMessageSource中存储了一个loopup的hashMap变量。
每次getMessage就是从这个HahsMap中获取。
而这个reader是根据spring.messages.basename 配置的值去实例化的。
四. 关于ResourceBundleMessageSource加载文件过程:接着第二个分析的第3个步骤开始
那么ResourceBundleMessageSource是在什么时候加载文件的呢
4. ResourceBundleMessageSource:getResourceBundle
//锁住当前缓存的cachedResourceBundles保证线程安全
//从baseName中获取当前的 localeMap
//根据locale获取bundle
//如果没有获取到缓存里面的bundle则通过doGetBundle去本地加载bundle然后再放入缓存当中。
//
protected ResourceBundle getResourceBundle(String basename, Locale locale) {
if (getCacheMillis() >= 0) {
return doGetBundle(basename, locale);
}
else {
synchronized (this.cachedResourceBundles) {
Map<Locale, ResourceBundle> localeMap = this.cachedResourceBundles.get(basename);
if (localeMap != null) {
ResourceBundle bundle = localeMap.get(locale);
if (bundle != null) {
return bundle;
}
}
try {
ResourceBundle bundle = doGetBundle(basename, locale);
if (localeMap == null) {
localeMap = new HashMap<Locale, ResourceBundle>();
this.cachedResourceBundles.put(basename, localeMap);
}
localeMap.put(locale, bundle);
return bundle;
}
catch (MissingResourceException ex) {
if (logger.isWarnEnabled()) {
logger.warn("ResourceBundle [" + basename + "] not found for MessageSource: " + ex.getMessage());
}
return null;
}
}
}
}
5. ResourceBundleMessageSource:doGetBundle
//返回了ResourceBundle.getBundle
protected ResourceBundle doGetBundle(String basename, Locale locale) throws MissingResourceException {
return ResourceBundle.getBundle(basename, locale, getBundleClassLoader(), new MessageSourceControl());
}
6:ResourceBu ndle.getBundle
//通过findBundle去加载bundle
public static ResourceBundle getBundle(String baseName, Locale targetLocale,
ClassLoader loader, Control control) {
if (loader == null || control == null) {
throw new NullPointerException();
}
return getBundleImpl(baseName, targetLocale, loader, control);
}
private static ResourceBundle getBundleImpl(String baseName, Locale locale,
ClassLoader loader, Control control) {
bundle = findBundle(cacheKey, candidateLocales, formats, 0, control, baseBundle);
return bundle;
}
7.ResourceBundle:findBundle
bundle = loadBundle(cacheKey, formats, control, expiredBundle);
8. ResourceBundle :findBundleInCache
bundle = control.newBundle(cacheKey.getName(), targetLocale, format,
cacheKey.getLoader(), reload);
9. ResourceBundleMessageSource :newBundle
return super.newBundle(baseName, locale, format, loader, reload);
10. ResourceBundle: newBundle
return loadBundle(new InputStreamReader(stream, encoding));
11. ResourceBundle: loadBundle
protected ResourceBundle loadBundle(Reader reader) throws IOException {
return new PropertyResourceBundle(reader);
}
12. PropertyResourceBundle
//接下来就是第三点
public PropertyResourceBundle (Reader reader) throws IOException {
Properties properties = new Properties();
properties.load(reader);
lookup = new HashMap(properties);
}
总结:message从cash中获取bundle ,缓存(cash)中没有的就去加载bundle,
用synchronized锁住cashbundle来保证线程安全。
大总结:
中上所述,在spring启动的时候,将ResourceBundleMessageSource实例化。
在每次请求到controller的时候 首先保存request到contextholder中。
在调用ResourceBundleMessageSource.getMessage的时候,
实现从caches中获取bundler 匹配到对应的bundl直接从bundl中的lookup(map)中获取值。
否则就去本地通过PropertyResourceBundle构造函数中Properties.load0去加载本地化资源。
加载的资源放置于缓存中。以便下次再来加载的时候更快。
标签:return,springboot,locale,request,bundle,源码,null,服务端,String 来源: https://blog.csdn.net/qq_27471259/article/details/97529231
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