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/*
 * =============================================================================
 * 
 *   Copyright (c) 2011-2014, The THYMELEAF team (http://www.thymeleaf.org)
 * 
 *   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 org.thymeleaf.spring4.messageresolver;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceAware;
import org.springframework.context.NoSuchMessageException;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.ITemplateProcessingContext;
import org.thymeleaf.exceptions.ConfigurationException;
import org.thymeleaf.messageresolver.AbstractMessageResolver;
import org.thymeleaf.messageresolver.MessageResolution;
import org.thymeleaf.util.Validate;



/**
 * 
 *   Implementation of {@link org.thymeleaf.messageresolver.IMessageResolver} that
 *   integrates the standard Spring way of resolving messages into Thymeleaf.
 * 
 * 
 *   This resolution is done by means of using the available Spring-configured
 *   {@link MessageSource} objects.  
 * 
 *
 * @author Daniel Fernández
 * 
 * @since 1.0 (reimplemented in 3.0.0)
 *
 */
public final class SpringMessageResolver
        extends AbstractMessageResolver 
        implements MessageSourceAware {


    private static final Logger logger = LoggerFactory.getLogger(SpringMessageResolver.class);


    private MessageSource messageSource;


    public SpringMessageResolver() {
        super();
    }





    /*
     * Check the message source has been set.
     */
    private void checkMessageSourceInitialized() {
        if (this.messageSource == null) {
            throw new ConfigurationException(
                    "Cannot initialize " + SpringMessageResolver.class.getSimpleName() +
                            ": MessageSource has not been set. Either define this object as " +
                            "a Spring bean (which will automatically set the MessageSource) or, " +
                            "if you instance it directly, set the MessageSource manually using its "+
                            "corresponding setter method.");
        }
    }





    /**
     * 
     *   Returns the message source ({@link MessageSource}) to be
     *   used for message resolution.
     * 
     *
     * @return the message source
     */
    public final MessageSource getMessageSource() {
        return this.messageSource;
    }


    /**
     * 
     *   Sets the message source to be used for message resolution
     * 
     *
     * @param messageSource the message source
     */
    public final void setMessageSource(final MessageSource messageSource) {
        this.messageSource = messageSource;
    }





    public MessageResolution resolveMessage(
            final ITemplateProcessingContext processingContext, final String key, final Object[] messageParameters) {

        Validate.notNull(processingContext, "Processing Context cannot be null");
        Validate.notNull(processingContext.getLocale(), "Locale in context cannot be null");
        Validate.notNull(key, "Message key cannot be null");

        checkMessageSourceInitialized();

        if (logger.isTraceEnabled()) {
            logger.trace(
                    "[THYMELEAF][{}] Resolving message with key \"{}\" for template \"{}\" and locale \"{}\". " +
                            "Messages will be retrieved from Spring's MessageSource infrastructure.",
                    new Object[] {TemplateEngine.threadIndex(), key, processingContext.getTemplateResolution().getTemplateName(), processingContext.getLocale()});
        }

        try {

            final String resolvedMessage =
                    this.messageSource.getMessage(key, messageParameters, processingContext.getLocale());

            return new MessageResolution(resolvedMessage);

        } catch (NoSuchMessageException e) {
            return null;
        }

    }



}