добавил пример локализации

http/examples.http

@@ -0,0 +1,3 @@
+### Запрос эндпойнта hello
+GET http://localhost:8080/hello?name=Петька
+Language: en

src/main/java/dev/struchkov/example/spring/i18n/AppConfig.java

@@ -0,0 +1,25 @@
+package dev.struchkov.example.spring.i18n;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.support.ReloadableResourceBundleMessageSource;
+import org.springframework.web.servlet.LocaleResolver;
+
+@Configuration
+public class AppConfig {
+
+    @Bean
+    public ReloadableResourceBundleMessageSource messageSource() {
+        ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
+        messageSource.setBasename("classpath:messages");
+        messageSource.setCacheSeconds(3600);
+        messageSource.setDefaultEncoding("UTF-8");
+        return messageSource;
+    }
+
+    @Bean
+    public LocaleResolver localeResolver() {
+        return new UserLocaleResolver();
+    }
+
+}

src/main/java/dev/struchkov/example/spring/i18n/HelloController.java

@@ -0,0 +1,23 @@
+package dev.struchkov.example.spring.i18n;
+
+import jakarta.servlet.http.HttpServletRequest;
+import lombok.RequiredArgsConstructor;
+import org.springframework.context.MessageSource;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.LocaleResolver;
+
+@RestController
+@RequiredArgsConstructor
+public class HelloController {
+
+    private final MessageSource messageSource;
+    private final LocaleResolver localeResolver;
+
+    @GetMapping("/hello")
+    public String hello(@RequestParam("name") String name, HttpServletRequest request) {
+        return messageSource.getMessage("welcome", new Object[]{name}, localeResolver.resolveLocale(request));
+    }
+
+}

src/main/java/dev/struchkov/example/spring/i18n/SpringBootI18nApplication.java

@@ -1,4 +1,4 @@
-package dev.struchkov.example.springbooti18n;
+package dev.struchkov.example.spring.i18n;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;

src/main/java/dev/struchkov/example/spring/i18n/UserLocaleResolver.java

@@ -0,0 +1,22 @@
+package dev.struchkov.example.spring.i18n;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.web.servlet.LocaleResolver;
+
+import java.util.Locale;
+
+public class UserLocaleResolver implements LocaleResolver {
+
+    @Override
+    public Locale resolveLocale(HttpServletRequest request) {
+        final String lang = request.getHeader("Language");
+        return Locale.forLanguageTag(lang);
+    }
+
+    @Override
+    public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
+        // Not needed for this example
+    }
+
+}

src/main/resources/application.yml

@@ -1 +0,0 @@
-

src/main/resources/messages_en.properties

@@ -0,0 +1 @@
+welcome=Hello, {0}!

src/main/resources/messages_ru.properties

@@ -0,0 +1 @@
+welcome=??????, {0}!