package com.nobody;

import java.util.Locale;

/**
 * @Description
 * @Author Mr.nobody
 * @Date 2021/4/15
 * @Version 1.0
 */
public class LocalTest {
    public static void main(String[] args) {
        Locale defaultLocale = Locale.getDefault();
        Locale chinaLocale = Locale.CHINA;
        Locale usLocale = Locale.US;
        Locale usLocale1 = new Locale("en", "US");
        System.out.println(defaultLocale);
        System.out.println(defaultLocale.getLanguage());
        System.out.println(defaultLocale.getCountry());
        System.out.println(chinaLocale);
        System.out.println(usLocale);
        System.out.println(usLocale1);
    }
}

//Output results
zh_CN
zh
CN
zh_CN
en_US
en_US

# In i18n_zh_CN.properties file
userName=dried tangerine peel

# In i18n_en_US.properties file
userName=Peel

Locale chinaLocale = Locale.CHINA;
ResourceBundle resourceBundle = ResourceBundle.getBundle("i18n", chinaLocale);
String userName = resourceBundle.getString("userName");
System.out.println(userName);

Locale usLocale = Locale.US;
resourceBundle = ResourceBundle.getBundle("i18n", usLocale);
userName = resourceBundle.getString("userName");
System.out.println(userName);

//Output results
dried tangerine peel
Peel

package org.springframework.boot.autoconfigure.context;

@Configuration
@ConditionalOnMissingBean(value = MessageSource.class, search = SearchStrategy.CURRENT)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Conditional(ResourceBundleCondition.class)
@EnableConfigurationProperties
public class MessageSourceAutoConfiguration {

    private static final Resource[] NO_RESOURCES = {};

    //We can do it in application Modify spring.com in the properties file The default value of the messages prefix, such as modifying the value of basename
    @Bean
    @ConfigurationProperties(prefix = "spring.messages")
    public MessageSourceProperties messageSourceProperties() {
        return new MessageSourceProperties();
    }

    //Generate a ResourceBundleMessageSource instance and inject it into the container
    @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());
        }

        //Read the configuration file under classpath *:
        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;
            }
        }

    }

}

package org.springframework.boot.autoconfigure.context;

/**
 * Configuration properties for Message Source.
 *
 * @author Stephane Nicoll
 * @author Kedar Joshi
 * @since 2.0.0
 */
public class MessageSourceProperties {

    /**
  * Comma-separated list of basenames (essentially a fully-qualified classpath
  * location), each following the ResourceBundle convention with relaxed support for
  * slash based locations. If it doesn't contain a package qualifier (such as
  * "org.mypackage"), it will be resolved from the classpath root.
  */
    private String basename = "messages";

    /**
  * Message bundles encoding.
  */
    private Charset encoding = StandardCharsets.UTF_8;

    /**
  * Loaded resource bundle files cache duration. When not set, bundles are cached
  * forever. If a duration suffix is not specified, seconds will be used.
  */
    @DurationUnit(ChronoUnit.SECONDS)
    private Duration cacheDuration;

    /**
  * Whether to fall back to the system Locale if no files for a specific Locale have
  * been found. if this is turned off, the only fallback will be the default file (e.g.
  * "messages.properties" for basename "messages").
  */
    private boolean fallbackToSystemLocale = true;

    /**
  * Whether to always apply the MessageFormat rules, parsing even messages without
  * arguments.
  */
    private boolean alwaysUseMessageFormat = false;

    /**
  * Whether to use the message code as the default message instead of throwing a
  * "NoSuchMessageException". Recommended during development only.
  */
    private boolean useCodeAsDefaultMessage = false;

    //Omit get/set
}

@Autowired
private MessageSource messageSource;

@GetMapping("test")
public GeneralResult<String> test() {
    //Obtain the Locale object of the client, that is, the value of the accept language key of the request header. We can also customize the request header key to obtain the language ID
    Locale locale = LocaleContextHolder.getLocale();
    String userName = messageSource.getMessage("userName", null, locale);
    System.out.println(userName);
    return GeneralResult.genSuccessResult(userName);
}