LanguageUtils.java

package com.salesmanager.admin.common.utils;

import com.salesmanager.admin.constants.Constants;
import com.salesmanager.core.business.services.reference.language.LanguageService;
import com.salesmanager.core.model.merchant.MerchantStore;
import com.salesmanager.core.model.reference.language.Language;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.stereotype.Service;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.support.RequestContextUtils;

import java.util.Locale;

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

/**
 * Created by umesh on 3/27/17.
 */
@Service
public class LanguageUtils {

    @Inject
    LanguageService languageService;

    /**
     * Determines request language based on store rules
     * @param request
     * @return
     */
    public Language getRequestLanguage(HttpServletRequest request, HttpServletResponse response) {

        Locale locale = null;

        Language language = (Language) request.getSession().getAttribute(Constants.LANGUAGE);


        if(language==null) {
            try {

                locale = LocaleContextHolder.getLocale();//should be browser locale


                MerchantStore store = (MerchantStore)request.getSession().getAttribute(Constants.MERCHANT_STORE);
                if(store!=null) {
                    language = store.getDefaultLanguage();
                    if(language!=null) {
                        locale = languageService.toLocale(language);
                        if(locale!=null) {
                            LocaleContextHolder.setLocale(locale);
                        }
                        request.getSession().setAttribute(Constants.LANGUAGE, language);
                    }

                    if(language==null) {
                        language = languageService.toLanguage(locale);
                        request.getSession().setAttribute(Constants.LANGUAGE, language);
                    }

                }

            } catch(Exception e) {
                if(language==null) {
                    try {
                        language = languageService.getByCode(Constants.DEFAULT_LANGUAGE);
                    } catch(Exception ignore) {}
                }
            }
        } else {


            Locale localeFromContext = LocaleContextHolder.getLocale();//should be browser locale
            if(!language.getCode().equals(localeFromContext.getLanguage())) {
                //get locale context
                language = languageService.toLanguage(localeFromContext);
            }

        }

        if(language != null) {
            locale = languageService.toLocale(language);
        } else {
            language = languageService.toLanguage(locale);
        }

        LocaleResolver localeResolver = RequestContextUtils.getLocaleResolver(request);
        if(localeResolver!=null) {
            localeResolver.setLocale(request, response, locale);
        }
        response.setLocale(locale);

        return language;
    }

    /**
     * Should be used by rest web services
     * @param request
     * @param store
     * @return
     * @throws Exception
     */
    public Language getRESTLanguage(HttpServletRequest request, MerchantStore store) throws Exception {

        Validate.notNull(request,"HttpServletRequest must not be null");
        Validate.notNull(store,"MerchantStore must not be null");

        Language language = null;


        String lang = request.getParameter(Constants.LANG);

        if(StringUtils.isBlank(lang)) {
            //try with HttpSession
            language = (Language) request.getSession().getAttribute(Constants.LANGUAGE);
            if(language==null) {
                language = store.getDefaultLanguage();
            }

            if(language==null) {
                language = languageService.defaultLanguage();
            }
        } else {
            language = languageService.getByCode(lang);
            if(language==null) {
                language = (Language) request.getSession().getAttribute(Constants.LANGUAGE);
                if(language==null) {
                    language = store.getDefaultLanguage();
                }

                if(language==null) {
                    language = languageService.defaultLanguage();
                }
            }
        }

        return language;
    }
}