org.apache.wicket.markup.repeater.AbstractRepeater.java Source code

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Here is the source code for org.apache.wicket.markup.repeater.AbstractRepeater.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket.markup.repeater;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.apache.wicket.Component;
import org.apache.wicket.DequeueContext;
import org.apache.wicket.DequeueContext.Bookmark;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.markup.IMarkupFragment;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.model.IModel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Base class for repeaters. This container renders each of its children using its own markup.
 * 
 * The children are collected using {@link #renderIterator()} method. This class will take care of
 * properly positioning and rewinding its markup stream so before each child renders it points to
 * the beginning of this component. Each child is rendered by a call to
 * {@link #renderChild(Component)}. A typical implementation simply does
 * <code>child.render();</code>.
 *
 * <strong>Note</strong>: the children are added during the render phase (in {@linkplain #beforeRender()} so
 * most of the specializations of this class should not be used as parents of
 * {@link org.apache.wicket.markup.html.form.FormComponent}s in stateless pages because the form components
 * will not be available during the action phase (i.e. at
 * {@link org.apache.wicket.markup.html.form.StatelessForm#onSubmit()}). Use
 * {@link org.apache.wicket.markup.repeater.RepeatingView} in these cases.
 *
 * @author Igor Vaynberg (ivaynberg)
 */
public abstract class AbstractRepeater extends WebMarkupContainer {
    private static final long serialVersionUID = 1L;

    private static final Logger log = LoggerFactory.getLogger(AbstractRepeater.class);

    /**
     * Constructor
     * 
     * @param id
     */
    public AbstractRepeater(String id) {
        super(id);
    }

    /**
     * Constructor
     * 
     * @param id
     * @param model
     */
    public AbstractRepeater(String id, IModel<?> model) {
        super(id, model);
    }

    /**
     * Returns an iterator for the collection of child components to be rendered. Users can override
     * this to change order of rendered children.
     * 
     * @return iterator over child components to be rendered
     */
    protected abstract Iterator<? extends Component> renderIterator();

    /**
     * Renders all child items in no specified order
     */
    @Override
    protected final void onRender() {
        Iterator<? extends Component> it = renderIterator();
        while (it.hasNext()) {
            Component child = it.next();
            if (child == null) {
                throw new IllegalStateException("The render iterator returned null for a child. Container: "
                        + this.toString() + "; Iterator=" + it.toString());
            }
            renderChild(child);
        }
    }

    /**
     * Render a single child. This method can be overridden to modify how a single child component
     * is rendered.
     * 
     * @param child
     *            Child component to be rendered
     */
    protected void renderChild(final Component child) {
        child.render();
    }

    /**
     * @see org.apache.wicket.Component#onBeforeRender()
     */
    @Override
    protected void onBeforeRender() {
        onPopulate();

        if (getApplication().usesDevelopmentConfig()) {
            Set<String> usedComponentIds = new HashSet<>();
            Iterator<? extends Component> i = iterator();
            while (i.hasNext()) {
                Component c = i.next();
                String componentId = c.getId();
                if (usedComponentIds.add(componentId) == false) {
                    log.warn("Repeater '{}' has multiple children with the same component id: '{}'",
                            getPageRelativePath(), componentId);
                    // do not flood the log
                    break;
                }
            }
        }
        super.onBeforeRender();
    }

    /**
     * @see org.apache.wicket.MarkupContainer#getMarkup(org.apache.wicket.Component)
     */
    @Override
    public IMarkupFragment getMarkup(final Component child) {
        // each direct child gets the markup of this repeater
        return getMarkup();
    }

    /**
     * Callback to let the repeater know it should populate itself with its items.
     */
    protected abstract void onPopulate();

    @Override
    public void dequeue(DequeueContext dequeue) {
        if (size() > 0) {
            // essentially what we do is for every child replace the repeater with the child in
            // dequeue container stack and run the dequeue on the child. we also take care to reset
            // the state of the dequeue context after we process every child.

            Bookmark bookmark = dequeue.save();

            for (Component child : this) {
                if (child instanceof MarkupContainer) {
                    dequeue.popContainer(); // pop the repeater
                    MarkupContainer container = (MarkupContainer) child;
                    dequeue.pushContainer(container);
                    container.dequeue(dequeue);
                    dequeue.restore(bookmark);
                }
            }
        }

        dequeue.skipToCloseTag();

    }
}