Spring MVC - 국제화(I18N: Internationalization)

15> 국제화(I18N: Internationalization)
- 로케일(locale) 에 따라 화면의 언어를 다르게 랜더링이 가능하다.
  다국어 처리가 가능하다.
- Spring 이 특정언어를 선택하는 방법
  ==> 기본적으로 LocaleResolver 를 이용해서 Locale 를 인식하여
      원하는 특정언어를 선택 가능.

  가. AcceptHeaderLocaleResolver
  - 요청 헤더값을 이용해서 locale 정보를 얻음.
  - Accept-language 헤더값 이용.
  - 기본적으로 적용되는 방법임.

  나. CookieLocaleResolver
  - 쿠키를 이용해서 locale 정보를 저장 및 얻음.
  - setLocale("ko|en");

  다. SessionLocaleResolve
  - 세션을 이용해서 locale 정보를 저장 및 얻음.
  - setLocale("ko|en");

- 구현1
(1) 리소스 번들 파일 작성(resource bundle 파일)
-> 문법:
        src/main/resources 폴더
              ㄴ파일명-언어코드.properties
-> 키=값
ex>
   기본번들파일: message.properties
                greeting=안녕하세요
   한국어 번들파일: message_ko.properties
                   greeting=안녕하세요   
   영어 번들파일: message_en.properties
                 greeting=hello
   일본어 번들파일: message_jp.properties
                   greeting=こんにちは

-> 번들파일의 인코딩은 모두 utf-8 로 변경

# message-en.properties
greerting=hello

# message-ko.properties
greerting=안녕하세요

# message.properties
greerting=안녕하세요. 기본값

(2) application.properties 에 리소스 번들 등록

# application.properties
# 리소스 번들 파일 등록
spring.messages.basename=bundle/message
spring.messages.encoding=utf-8

  # message.properties
  greeting=안녕하세요. 기본값

  # message_ko.properties
  greeting=안녕하세요

  # message_en.properties
  greeting=hello

(3) spring.messages.fallback-to-system-locale=false
기본: true.  message.properties 가 아닌 system 의 locale(제어판의 국가별 설정) 적용함.
      false. message.properties 적용.

///////////////////////////////////////////////////
#application.properties 에서 I18N 설정(종합)
# 리소스 번들 파일 등록
spring.messages.basename=bundle/message
spring.messages.encoding=utf-8

spring.messages.fallback-to-system-locale=false
///////////////////////////////////////////////////

# application.properties
logging.level.org.springframework=info

# tomcat port 번호 변경
server.port=8090

# context 명 변경
server.servlet.context-path=/app

# jsp의 경로와 확장자 지정
spring.mvc.view.prefix=/WEB-INF/views/
spring.mvc.view.suffix=.jsp

# 리소스 번들 파일 등록
spring.messages.basename=bundle/message
spring.messages.encoding=utf-8

spring.messages.fallback-to-system-locale=false

(4) SessionLocaleResolver 생성

  @Configuration
  public class WebMvc {

    // 기본인 AcceptHeaderLocaleResolver 인데
    // 기본을 SessionLocaleResolver로 변경하는 작업이다.
    @Bean
    public SessionLocaleResolver localeResolver() {
      SessionLocaleResolver locale =
          new SessionLocaleResolver();
      locale.setDefaultLocale(new Locale("ko"));
      return locale;
    }
  }

package com.exam.config;

import java.util.Locale;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.i18n.SessionLocaleResolver;

@Configuration
public class WebMvc {

	// 기본인 AcceptHeaderLocaleResolver 인데
	// 기본을 SessionLocaleResolver로 변경하는 작업이다.
	@Bean
	public SessionLocaleResolver localeResolver() {
		SessionLocaleResolver locale =
				new SessionLocaleResolver();
		locale.setDefaultLocale(new Locale("ko"));
		return locale;
	}
}

(5) Controller 에서 개발자가 직접 locale 변경(명시적)

@GetMapping("/bundle")
public String bundle( HttpServletRequest request,
              HttpServletResponse response,
          @RequestParam String lang) {

//SessionLocaleResolver의 로케일을 변경.
locale.setLocale(request, response,
new Locale(lang));

Locale xxx =  LocaleContextHolder.getLocale();
System.out.println("현재 로케일2:" +  xxx);

return "show";
}

package com.exam.controller;

import java.util.Locale;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.i18n.SessionLocaleResolver;

@Controller
public class MainController {
	
	Logger logger = LoggerFactory.getLogger(getClass());
	
	@Autowired
	SessionLocaleResolver locale;
	
	@GetMapping("/main")
	public String main() {
		Locale xxx =  LocaleContextHolder.getLocale();
		System.out.println("현재 로케일1:" +  xxx);
		return "main";
	}
	
	@GetMapping("/bundle")
	public String bundle( HttpServletRequest request,
			              HttpServletResponse response,
			          @RequestParam String lang) {
		
		//SessionLocaleResolver의 로케일을 변경.
		locale.setLocale(request, response,
				new Locale(lang));
		
		Locale xxx =  LocaleContextHolder.getLocale();
		System.out.println("현재 로케일2:" +  xxx);
		
		return "show";
	}
	
}

package com.exam;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;


@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
}

<%@ page 
         contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8"        
%>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>main.jsp</h2>
<p>안녕하세요</p>
<a href="bundle?lang=en">영어</a><br>
<a href="bundle?lang=ko">한국어</a><br>
<a href="bundle?lang=jp">일본어</a><br>
</body>
</html>

<%@ page 
         contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8"        
%>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>show.jsp</h2>
bundle message:<spring:message code="greerting" 
                text="default값"></spring:message>
</body>
</html>

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
	http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.18</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.exam</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>11</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
		<dependency>
		    <groupId>org.springframework.boot</groupId>
		    <artifactId>spring-boot-devtools</artifactId>
		</dependency>
	<dependency>
		<groupId>org.apache.tomcat.embed</groupId>
		<artifactId>tomcat-embed-jasper</artifactId>
		<scope>provided</scope>
	</dependency> 
	<dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>jstl</artifactId>
	</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

- 구현2
(1) LocalechangeInterceptor 이용해서 로케일 변경해줌.
    따라서 Controller 에서 명시적으로 setLocale(new Locale("값")) 할 필요가 없음.

  @Configuration
  public class WebMvc implements WebMvcConfigurer {

    // 기본인 AcceptHeaderLocaleResolver 인데
    // 기본을 SessionLocaleResolver로 변경하는 작업이다.
    @Bean
    public SessionLocaleResolver localeResolver() {
      SessionLocaleResolver locale =
          new SessionLocaleResolver();
      locale.setDefaultLocale(new Locale("ko"));
      return locale;
    }
    
    // LocalChangeInterceptor 생성
    @Bean
    public LocaleChangeInterceptor changeInterceptor() {
      
      LocaleChangeInterceptor xxx = new LocaleChangeInterceptor();
      // ?lang=en|ko|jp 의 값을 changeInterceptor 자동으로 세팅해줌.
      xxx.setParamName("lang"); // lange 의 값을 changeInterceptor 세팅해줌.
      
      return xxx;
    }
    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
      registry.addInterceptor(changeInterceptor());
    }
    
  }

package com.exam.config;

import java.util.Locale;

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

@Configuration
public class WebMvc implements WebMvcConfigurer {

	// 기본인 AcceptHeaderLocaleResolver 인데
	// 기본을 SessionLocaleResolver로 변경하는 작업이다.
	@Bean
	public SessionLocaleResolver localeResolver() {
		SessionLocaleResolver locale =
				new SessionLocaleResolver();
		locale.setDefaultLocale(new Locale("ko"));
		return locale;
	}
	
	// LocalChangeInterceptor 생성
	@Bean
	public LocaleChangeInterceptor changeInterceptor() {
		
		LocaleChangeInterceptor xxx = new LocaleChangeInterceptor();
		// ?lang=en|ko|jp 의 값을 changeInterceptor 자동으로 세팅해줌.
		xxx.setParamName("lang"); // lange 의 값을 changeInterceptor 세팅해줌.
		
		return xxx;
	}
	
	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		registry.addInterceptor(changeInterceptor());
	}
	
}