jakarta.mvc.locale.LocaleResolver Maven / Gradle / Ivy

Go to download
/*
 * Copyright (c) 2016-2017 JSR 371 expert group and contributors
 * Copyright (c) 2020 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */
package jakarta.mvc.locale;

import jakarta.mvc.MvcContext;
import java.util.Locale;

/**
 * Locale resolvers are used to determine the locale of the current request and are discovered
 * using Jakarta Contexts and Dependency Injection.
 *
 * The Jakarta MVC implementation is required to resolve the locale for each request following this
 * algorithm:
 *
 * 
 * Gather the set of all implementations of this interface available for injection via
 * CDI.
 * Sort the set of implementations using priorities in descending order. Locale resolvers
 * can be decorated with {@link jakarta.annotation.Priority} to indicate their priority. If no
 * priority is explicitly defined, the priority is assumed to be 1000.
 * Call the method {@link #resolveLocale(LocaleResolverContext)}. If the resolver returns
 * a valid locale, use this locale as the request locale. If the resolver returns
 * null, proceed with the next resolver in the ordered set.
 * 
 *
 * Controllers, view engines and other components can access the resolved locale by calling
 * {@link MvcContext#getLocale()}.
 *
 * The MVC implementation is required to provide a default locale resolver with a priority
 * of 0 which uses the Accept-Language request header to obtain the
 * locale. If resolving the locale this way isn't possible, the default resolver must return
 * {@link Locale#getDefault()}.
 *
 * @author Christian Kaltepoth
 * @author Ivar Grimstad
 * @see jakarta.mvc.locale.LocaleResolverContext
 * @see MvcContext#getLocale()
 * @see java.util.Locale
 * @since 1.0
 */
public interface LocaleResolver {

    /**
     * Resolve the locale of the current request given a {@link LocaleResolverContext}.
     *
     * If the implementation is able to resolve the locale for the request, the corresponding
     * locale must be returned. If the implementation cannot resolve the locale, it must return
     * null. In this case the resolving process will continue with the next
     * resolver.
     *
     * @param context the context needed for processing.
     * @return The resolved locale or null.
     */
    Locale resolveLocale(LocaleResolverContext context);

}