SpringBoot本身提供了很好的国际化的封装，通过简单的配置即可使用，极大提高了开发效率。
使用
在配置文件中增加以下配置：
spring:
messages:
basename: i18n/messages
fallbackToSystemLocale: false然后就可以在src/main/resources下增加相关的i18n文件了，如下：
这里messages.properties是作为兜底策略存在的，当根据一定的查找策略找不到i18n文件后，会使用该文件的信息返回。那么框架本身是基于什么样的策略查找i18n文件的呢？继续往下看。
技术实现
自动配置
SpringBoot是基于MessageSourceAutoConfiguration进行自动配置初始化，代码如下：
@AutoConfiguration
@ConditionalOnMissingBean(name = AbstractApplicationContext.MESSAGE_SOURCE_BEAN_NAME, search = SearchStrategy.CURRENT)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Conditional(ResourceBundleCondition.class)
@EnableConfigurationProperties
public class MessageSourceAutoConfiguration {
private static final Resource[] NO_RESOURCES = {};
@Bean
@ConfigurationProperties(prefix = "spring.messages")
public MessageSourceProperties messageSourceProperties() {
return new MessageSourceProperties();
}
@Bean
public MessageSource messageSource(MessageSourceProperties properties) {
ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
if (StringUtils.hasText(properties.getBasename())) {
messageSource.setBasenames(StringUtils
.commaDelimitedListToStringArray(StringUtils.trimAllWhitespace(properties.getBasename())));
}
if (properties.getEncoding() != null) {
messageSource.setDefaultEncoding(properties.getEncoding().name());
}
messageSource.setFallbackToSystemLocale(properties.isFallbackToSystemLocale());
Duration cacheDuration = properties.getCacheDuration();
if (cacheDuration != null) {
messageSource.setCacheMillis(cacheDuration.toMillis());
}
messageSource.setAlwaysUseMessageFormat(properties.isAlwaysUseMessageFormat());
messageSource.setUseCodeAsDefaultMessage(properties.isUseCodeAsDefaultMessage());
return messageSource;
}
protected static class ResourceBundleCondition extends SpringBootCondition {
private static ConcurrentReferenceHashMap<String, ConditionOutcome> cache = new ConcurrentReferenceHashMap<>();
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
String basename = context.getEnvironment().getProperty("spring.messages.basename", "messages");
ConditionOutcome outcome = cache.get(basename);
if (outcome == null) {
outcome = getMatchOutcomeForBasename(context, basename);
cache.put(basename, outcome);
}
return outcome;
}
private ConditionOutcome getMatchOutcomeForBasename(ConditionContext context, String basename) {
ConditionMessage.Builder message = ConditionMessage.forCondition("ResourceBundle");
for (String name : StringUtils.commaDelimitedListToStringArray(StringUtils.trimAllWhitespace(basename))) {
for (Resource resource : getResources(context.getClassLoader(), name)) {
if (resource.exists()) {
return ConditionOutcome.match(message.found("bundle").items(resource));
}
}
}
return ConditionOutcome.noMatch(message.didNotFind("bundle with basename " + basename).atAll());
}
private Resource[] getResources(ClassLoader classLoader, String name) {
String target = name.replace('.', '/');
try {
return new PathMatchingResourcePatternResolver(classLoader)
.getResources("classpath*:" + target + ".properties");
}
catch (Exception ex) {
return NO_RESOURCES;
}
}
}
}i18n文件查找策略
在开始查找策略之前先介绍下几个概念：
language：语种，例如：中文、英文script：洲，例如亚洲、拉丁美洲等country：国家，例如中国variant：方言，例如闽南语、四川话等
i18n文件查找策略详见java.util.ResourceBundle，优先级如下：
baseName + "_" + language + "_" + script + "_" + country + "_" + variant
baseName + "_" + language + "_" + script + "_" + country
baseName + "_" + language + "_" + script
baseName + "_" + language + "_" + country + "_" + variant
baseName + "_" + language + "_" + country
baseName + "_" + language举例来说：
MyResource_en_Latn_US_WINDOWS_VISTA
MyResource_en_Latn_US_WINDOWS
MyResource_en_Latn_US
MyResource_en_Latn
MyResource_en_US_WINDOWS_VISTA
MyResource_en_US_WINDOWS
MyResource_en_US
MyResource_en
