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/*
 * =============================================================================
 * 
 *   Copyright (c) 2011-2016, 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.ITemplateContext;
import org.thymeleaf.exceptions.ConfigurationException;
import org.thymeleaf.messageresolver.AbstractMessageResolver;
import org.thymeleaf.messageresolver.IMessageResolver;
import org.thymeleaf.messageresolver.StandardMessageResolver;
import org.thymeleaf.util.Validate;



/**
 * 
 *   Implementation of {@link IMessageResolver} that
 *   integrates the standard Spring way of resolving messages into Thymeleaf.
 * 
 * 
 *   Template-based resolution is done by means of using the available Spring-configured
 *   {@link MessageSource} objects.  
 * 
 * 
 *   Origin-based resolution is done in exactly the same way as in {@link StandardMessageResolver}.
 * 
 *
 * @author Daniel Fernández
 * 
 * @since 3.0.0
 *
 */
public class SpringMessageResolver
        extends AbstractMessageResolver 
        implements MessageSourceAware {


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


    private final StandardMessageResolver standardMessageResolver;
    private MessageSource messageSource;


    public SpringMessageResolver() {
        super();
        this.standardMessageResolver = new StandardMessageResolver();
    }





    /*
     * 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 final String resolveMessage(
            final ITemplateContext context, final Class origin, final String key, final Object[] messageParameters) {

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

        /*
         * FIRST STEP: Look for the message using template-based resolution
         */
        if (context != 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, context.getTemplateData().getTemplate(), context.getLocale()});
            }

            try {
                return this.messageSource.getMessage(key, messageParameters, context.getLocale());
            } catch (NoSuchMessageException e) {
                // Try other methods
            }

        }

        /*
         * SECOND STEP: Look for the message using origin-based resolution, delegated to the StandardMessageResolver
         */
        if (origin != null) {
            // We will be using context == null when delegating so that only origin-based resolution is performed
            final String message = this.standardMessageResolver.resolveMessage(null, origin, key, messageParameters);
            if (message != null) {
                return message;
            }
        }


        /*
         * NOT FOUND, return null
         */
        return null;

    }




    public String createAbsentMessageRepresentation(
            final ITemplateContext context, final Class origin, final String key, final Object[] messageParameters) {
        return this.standardMessageResolver.createAbsentMessageRepresentation(context, origin, key, messageParameters);
    }

}