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feat: add translation file request handler (#18680)
This PR adds a request handler to serve translation properties files. For the request to be handled by this handler, the request type should be i18n. There is one optional parameter to construct the locale: langtag. If a translation properties file that corresponds to the locale, the response contains the translation entries in JSON format. Otherwise, it contains the default file or returns a not found response. The default file is the bundle for the root locale. The system default locale is not considered to be the default, and is not used for fallback. The response header also contains information regarding the retrieved file locale. Fixes #18641
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flow-server/src/main/java/com/vaadin/flow/i18n/TranslationFileRequestHandler.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,229 @@ | ||
| /* | ||
| * Copyright 2000-2024 Vaadin Ltd. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not | ||
| * use this file except in compliance with the License. You may obtain a copy of | ||
| * the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| * License for the specific language governing permissions and limitations under | ||
| * the License. | ||
| */ | ||
| package com.vaadin.flow.i18n; | ||
|
|
||
| import com.vaadin.flow.server.HandlerHelper; | ||
| import com.vaadin.flow.server.HttpStatusCode; | ||
| import com.vaadin.flow.server.SynchronizedRequestHandler; | ||
| import com.vaadin.flow.server.VaadinRequest; | ||
| import com.vaadin.flow.server.VaadinResponse; | ||
| import com.vaadin.flow.server.VaadinSession; | ||
| import elemental.json.Json; | ||
| import elemental.json.JsonObject; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
|
|
||
| import java.io.IOException; | ||
| import java.util.Locale; | ||
| import java.util.MissingResourceException; | ||
| import java.util.Objects; | ||
| import java.util.Optional; | ||
| import java.util.ResourceBundle; | ||
| import java.util.Set; | ||
|
|
||
| /** | ||
| * Handles translation file requests. Translation file requests are internal | ||
| * requests sent by the client-side to retrieve the translation file for the | ||
| * specified language tag. The response contains the translations in JSON | ||
| * format. Also, the language tag of the retrieved translation file is included | ||
| * as a header with the name {@code X-Vaadin-Retrieved-Locale}. The language tag | ||
| * parameter {@code langtag} supports both dash and underscore as separators. | ||
| * <p> | ||
| * The translation file to return is determined by matching the requested locale | ||
| * to the available bundles with the following prioritization order: | ||
| * <ul> | ||
| * <li>Exact match</li> | ||
| * <li>Language and country match</li> | ||
| * <li>Language match</li> | ||
| * <li>Default bundle (root bundle)</li> | ||
| * </ul> | ||
| * <p> | ||
| * For internal use only. May be renamed or removed in a future release. | ||
| * | ||
| * @author Vaadin Ltd | ||
| * @since 24.4 | ||
| */ | ||
| public class TranslationFileRequestHandler extends SynchronizedRequestHandler { | ||
|
|
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| static final String LANGUAGE_TAG_PARAMETER_NAME = "langtag"; | ||
|
|
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| static final String RETRIEVED_LOCALE_HEADER_NAME = "X-Vaadin-Retrieved-Locale"; | ||
|
|
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| private static final Locale FALLBACK_LOCALE = Locale.ROOT; | ||
|
|
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| private final DefaultI18NProvider i18NProvider; | ||
|
|
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| private final boolean hasFallbackBundle; | ||
|
|
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| public TranslationFileRequestHandler(I18NProvider i18NProvider) { | ||
| boolean hasDefaultI18NProvider = i18NProvider != null | ||
| && DefaultI18NProvider.class.equals(i18NProvider.getClass()); | ||
| this.i18NProvider = hasDefaultI18NProvider | ||
| ? (DefaultI18NProvider) i18NProvider | ||
| : null; | ||
| this.hasFallbackBundle = hasFallbackBundle(); | ||
| } | ||
|
|
||
| @Override | ||
| public boolean synchronizedHandleRequest(VaadinSession session, | ||
| VaadinRequest request, VaadinResponse response) throws IOException { | ||
| if (i18NProvider == null) { | ||
| handleCustomI18NProvider(session, response); | ||
| return true; | ||
| } | ||
| Locale locale = getLocale(request); | ||
| ResourceBundle translationPropertyFile = getTranslationPropertyFile( | ||
| locale); | ||
| if (translationPropertyFile == null) { | ||
| handleNotFound(response); | ||
| } else { | ||
| handleFound(response, translationPropertyFile); | ||
| } | ||
| return true; | ||
| } | ||
|
|
||
| @Override | ||
| protected boolean canHandleRequest(VaadinRequest request) { | ||
| return HandlerHelper.isRequestType(request, | ||
| HandlerHelper.RequestType.TRANSLATION_FILE); | ||
| } | ||
|
|
||
| private void handleFound(VaadinResponse response, | ||
| ResourceBundle translationPropertyFile) throws IOException { | ||
| response.setStatus(HttpStatusCode.OK.getCode()); | ||
| response.setHeader(RETRIEVED_LOCALE_HEADER_NAME, | ||
| translationPropertyFile.getLocale().toLanguageTag()); | ||
| writeFileToResponse(response, translationPropertyFile); | ||
| } | ||
|
|
||
| private void handleNotFound(VaadinResponse response) { | ||
| response.setStatus(HttpStatusCode.NOT_FOUND.getCode()); | ||
| } | ||
|
|
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| private void handleCustomI18NProvider(VaadinSession session, | ||
| VaadinResponse response) throws IOException { | ||
| String errorMessage = "Loading translations is not supported when using a custom i18n provider."; | ||
| if (session.getService().getDeploymentConfiguration() | ||
| .isProductionMode()) { | ||
| response.setStatus(HttpStatusCode.NOT_FOUND.getCode()); | ||
| } else { | ||
| response.sendError(HttpStatusCode.NOT_IMPLEMENTED.getCode(), | ||
| errorMessage); | ||
| } | ||
| getLogger().debug(errorMessage); | ||
| } | ||
|
|
||
| private void writeFileToResponse(VaadinResponse response, | ||
| ResourceBundle translationPropertyFile) throws IOException { | ||
| JsonObject json = Json.createObject(); | ||
| translationPropertyFile.keySet().forEach( | ||
| key -> json.put(key, translationPropertyFile.getString(key))); | ||
| response.getWriter().write(json.toJson()); | ||
| } | ||
|
|
||
| private Locale getLocale(VaadinRequest request) { | ||
| String languageTag = Objects.requireNonNullElse( | ||
| request.getParameter(LANGUAGE_TAG_PARAMETER_NAME), ""); | ||
| if (languageTag.contains("_")) { | ||
| String[] tokens = languageTag.split("_"); | ||
| String language = tokens[0]; | ||
| String country = tokens.length > 1 ? tokens[1] : ""; | ||
| String variant = tokens.length > 2 ? tokens[2] : ""; | ||
| return new Locale(language, country, variant); | ||
| } | ||
| return Locale.forLanguageTag(languageTag); | ||
| } | ||
|
|
||
| private ResourceBundle getTranslationPropertyFile(Locale locale) { | ||
| Locale bestMatchLocale = getBestMatchLocale(locale); | ||
| if (bestMatchLocale == null) { | ||
| if (FALLBACK_LOCALE.equals(locale)) { | ||
| getLogger().debug( | ||
| "Missing the requested default bundle for {}.", | ||
| DefaultI18NProvider.BUNDLE_PREFIX); | ||
| } else { | ||
| getLogger().debug( | ||
| "Missing resource bundles for {}, both the requested locale {} and the default bundle.", | ||
| DefaultI18NProvider.BUNDLE_PREFIX, | ||
| locale.getDisplayName()); | ||
| } | ||
| return null; | ||
| } | ||
| if (!locale.equals(bestMatchLocale)) { | ||
| if (FALLBACK_LOCALE.equals(bestMatchLocale)) { | ||
| getLogger().debug( | ||
| "Missing resource bundle for {} and locale {}. Using the default bundle.", | ||
| DefaultI18NProvider.BUNDLE_PREFIX, | ||
| locale.getDisplayName()); | ||
| } else { | ||
| getLogger().debug( | ||
| "Missing resource bundle for {} and locale {}. Using the best match locale {}.", | ||
| DefaultI18NProvider.BUNDLE_PREFIX, | ||
| locale.getDisplayName(), | ||
| bestMatchLocale.getDisplayName()); | ||
| } | ||
| } | ||
| return i18NProvider.getBundle(bestMatchLocale, | ||
| ResourceBundle.Control.getNoFallbackControl( | ||
| ResourceBundle.Control.FORMAT_PROPERTIES)); | ||
| } | ||
|
|
||
| private Locale getBestMatchLocale(Locale locale) { | ||
| Set<Locale> providedLocales = Set | ||
| .copyOf(i18NProvider.getProvidedLocales()); | ||
| if (providedLocales.contains(locale)) { | ||
| return locale; | ||
| } | ||
| Optional<Locale> languageAndCountryMatch = providedLocales.stream() | ||
| .filter(providedLocale -> providedLocale.getLanguage() | ||
| .equals(locale.getLanguage()) | ||
| && providedLocale.getCountry() | ||
| .equals(locale.getCountry())) | ||
| .findAny(); | ||
| if (languageAndCountryMatch.isPresent()) { | ||
| return languageAndCountryMatch.get(); | ||
| } | ||
| Optional<Locale> languageMatch = providedLocales.stream() | ||
| .filter(providedLocale -> providedLocale.getLanguage() | ||
| .equals(locale.getLanguage())) | ||
| .findAny(); | ||
| if (languageMatch.isPresent()) { | ||
| return languageMatch.get(); | ||
| } | ||
| if (hasFallbackBundle) { | ||
| return FALLBACK_LOCALE; | ||
| } | ||
| return null; | ||
| } | ||
|
|
||
| private boolean hasFallbackBundle() { | ||
| if (this.i18NProvider != null) { | ||
| try { | ||
| this.i18NProvider.getBundle(FALLBACK_LOCALE, | ||
| ResourceBundle.Control.getNoFallbackControl( | ||
| ResourceBundle.Control.FORMAT_PROPERTIES)); | ||
| return true; | ||
| } catch (MissingResourceException e) { | ||
| // NO-OP | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
|
|
||
| private Logger getLogger() { | ||
| return LoggerFactory.getLogger(TranslationFileRequestHandler.class); | ||
| } | ||
| } |
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