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Thymeleaf Layout Dialect rewritten in java.
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/*
 * Copyright 2013, Emanuel Rabina (http://www.ultraq.net.nz/)
 *
 * 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 nz.net.ultraq.thymeleaf.includes;

import java.util.List;
import java.util.Map;
import nz.net.ultraq.thymeleaf.expressions.ExpressionProcessor;
import nz.net.ultraq.thymeleaf.fragments.FragmentFinder;
import nz.net.ultraq.thymeleaf.fragments.FragmentMap;
import nz.net.ultraq.thymeleaf.fragments.FragmentParameterNamesExtractor;
import nz.net.ultraq.thymeleaf.fragments.FragmentProcessor;
import nz.net.ultraq.thymeleaf.internal.MetaClass;
import nz.net.ultraq.thymeleaf.models.TemplateModelFinder;
import org.thymeleaf.context.ITemplateContext;
import org.thymeleaf.engine.AttributeName;
import org.thymeleaf.engine.TemplateModel;
import org.thymeleaf.model.IModel;
import org.thymeleaf.model.IProcessableElementTag;
import org.thymeleaf.processor.element.AbstractAttributeModelProcessor;
import org.thymeleaf.processor.element.IElementModelStructureHandler;
import org.thymeleaf.standard.expression.Assignation;
import org.thymeleaf.standard.expression.AssignationSequence;
import org.thymeleaf.standard.expression.FragmentExpression;
import org.thymeleaf.templatemode.TemplateMode;

/**
 * Similar to Thymeleaf's {@code th:replace}, but allows the passing of entire
 * element fragments to the included template. Useful if you have some HTML that
 * you want to reuse, but whose contents are too complex to determine or
 * construct with context variables alone.
 *
 * @author Emanuel Rabina
 */
public class ReplaceProcessor extends AbstractAttributeModelProcessor {

    public static final String PROCESSOR_NAME = "replace";
    public static final int PROCESSOR_PRECEDENCE = 0;

    /**
     * Constructor, set this processor to work on the 'replace' attribute.
     *
     * @param templateMode
     * @param dialectPrefix
     */
    public ReplaceProcessor(TemplateMode templateMode, String dialectPrefix) {
        super(templateMode, dialectPrefix, null, false, PROCESSOR_NAME, true, PROCESSOR_PRECEDENCE, true);
    }

    /**
     * Locates a page fragment and uses it to replace the current element.
     *
     * @param context
     * @param model
     * @param attributeName
     * @param attributeValue
     * @param structureHandler
     */
    @Override
    protected void doProcess(ITemplateContext context, IModel model, AttributeName attributeName,
            String attributeValue, IElementModelStructureHandler structureHandler) {

        // Locate the page and fragment to use for replacement
        FragmentExpression fragmentExpression = new ExpressionProcessor(context).parseFragmentExpression(attributeValue);
        TemplateModel fragmentForReplacement = new TemplateModelFinder(context).findFragment(fragmentExpression, getDialectPrefix());

        // Gather all fragment parts within the include element, scoping them to this element
        Map includeFragments = new FragmentFinder(getDialectPrefix()).findFragments(model);
        FragmentMap.setForNode(context, structureHandler, includeFragments);

        // Keep track of what template is being processed?  Thymeleaf does this for
        // its include processor, so I'm just doing the same here.
        structureHandler.setTemplateData(fragmentForReplacement.getTemplateData());

        // Replace this element with the located fragment
        IModel fragmentForReplacementUse = fragmentForReplacement.cloneModel();
        MetaClass.replaceModel(model, 0, fragmentForReplacementUse);

        // When fragment parameters aren't named, derive the name from the fragment definition
        // TODO: Common code across all the inclusion processors
        if (fragmentExpression.hasSyntheticParameters()) {
            String fragmentDefinition = ((IProcessableElementTag) MetaClass.first(fragmentForReplacementUse)).getAttributeValue(getDialectPrefix(), FragmentProcessor.PROCESSOR_NAME);
            List parameterNames = new FragmentParameterNamesExtractor().extract(fragmentDefinition);

            AssignationSequence parameters = fragmentExpression.getParameters();
            if (parameters != null) {
                int index = 0;
                for (Assignation parameter : parameters) {
                    structureHandler.setLocalVariable(parameterNames.get(index), parameter.getRight().execute(context));
                    ++index;
                }
            }
        } else { // Otherwise, apply values as is
            AssignationSequence parameters = fragmentExpression.getParameters();
            if (parameters != null) {
                for (Assignation parameter : parameters) {
                    structureHandler.setLocalVariable((String) parameter.getLeft().execute(context), parameter.getRight().execute(context));
                }
            }
        }
    }

}