こうした上で、クエリ文字列に language=言語(JP)などを入れないと、クッキーに出力されない。

WebConfig.java

import javax.servlet.ServletContext;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.ServletContextAware;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.i18n.CookieLocaleResolver;
import org.springframework.web.servlet.i18n.LocaleChangeInterceptor;

@Configuration
public class WebConfig implements ServletContextAware, WebMvcConfigurer {

	ServletContext context;

	@Bean
	public LocaleResolver localeResolver() {
		CookieLocaleResolver resolver = new CookieLocaleResolver();
		resolver.setCookiePath(context.getContextPath());
		resolver.setDefaultLocale(Locale.JAPAN);
		resolver.setCookieName("sampleLocaleResolveCookie");
		return resolver;
	}

	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		registry.addInterceptor(localeChangeInterceptor());
	}

	@Bean
	public LocaleChangeInterceptor localeChangeInterceptor() {
		LocaleChangeInterceptor localeChangeInterceptor = new LocaleChangeInterceptor();
		localeChangeInterceptor.setParamName("language");
		return localeChangeInterceptor;
	}

	@Override
	public void setServletContext(ServletContext servletContext) {
		this.context = servletContext;
	}

}