at.molindo.wicketutils.dev.MarkupSourceAttributeAppender.java Source code

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Here is the source code for at.molindo.wicketutils.dev.MarkupSourceAttributeAppender.java

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/**
 * Copyright 2010 Molindo GmbH
 *
 * 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 at.molindo.wicketutils.dev;

import java.lang.reflect.Field;

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.application.IComponentInstantiationListener;
import org.apache.wicket.markup.MarkupStream;
import org.apache.wicket.markup.html.panel.Fragment;
import org.apache.wicket.model.LoadableDetachableModel;
import org.apache.wicket.util.resource.IResourceStream;

/**
 * adds an {@link AttributeModifier} to every component with asscociated markup,
 * i.e., objects of any class extending
 * {@link WebMarkupContainerWithAssociatedMarkup}.
 * 
 * @author stf@molindo.at
 */
public final class MarkupSourceAttributeAppender implements IComponentInstantiationListener {

    private final String attribute;

    public MarkupSourceAttributeAppender(String attribute) {

        if (attribute == null) {
            throw new NullPointerException("attribute");
        }
        this.attribute = attribute;
    }

    @Override
    public void onInstantiation(final Component component) {
        if (component instanceof MarkupContainer) {
            component.add(new AttributeModifier(attribute, new MarkupSourceModel((MarkupContainer) component)));
        }
    }

    private static final class MarkupSourceModel extends LoadableDetachableModel<CharSequence> {

        private static final long serialVersionUID = 1L;

        private final MarkupContainer component;

        private MarkupSourceModel(MarkupContainer component) {
            this.component = component;
        }

        @Override
        protected CharSequence load() {
            MarkupStream stream = component.getAssociatedMarkupStream(false);
            if (stream == null || stream.getResource() == null) {
                return AttributeModifier.VALUELESS_ATTRIBUTE_REMOVE;
            }

            String resource = toString(stream.getResource());

            if (component instanceof Fragment) {
                resource += " [wicket:fragment=" + getFragmentId((Fragment) component) + "]";
            }

            return resource;
        }

        private String getFragmentId(Fragment fragment) {
            Field field;
            try {
                field = Fragment.class.getDeclaredField("markupId");
                field.setAccessible(true);
                return (String) field.get(fragment);
            } catch (NoSuchFieldException e) {
                throw new WicketRuntimeException("field 'markupId' of Fragment doesn't exist", e);
            } catch (Exception e) {
                return "<unknown>";
            }
        }

        /**
         * @param resource
         *            never null
         * @return a string describing this resource's location
         */
        private String toString(IResourceStream resource) {
            return resource.toString();
        }
    }
}