dropdownchoice.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * 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.html.form;

import java.util.List;

import org.apache.wicket.RequestContext;
import org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.model.IModel;
import org.apache.wicket.protocol.http.portlet.PortletRequestContext;


/**
 * A choice implemented as a dropdown menu/list.
 * <p>
 * Java:
 * 
 * <pre>
 * List SITES = Arrays.asList(new String[] { &quot;The Server Side&quot;, &quot;Java Lobby&quot;, &quot;Java.Net&quot; });
 * 
 * // Add a dropdown choice component that uses Input's 'site' property to designate the
 * // current selection, and that uses the SITES list for the available options.
 * // Note that when the selection is null, Wicket will lookup a localized string to
 * // represent this null with key: &quot;id + '.null'&quot;. In this case, this is 'site.null'
 * // which can be found in DropDownChoicePage.properties
 * form.add(new DropDownChoice(&quot;site&quot;, SITES));
 * </pre>
 * 
 * HTML:
 * 
 * <pre>
 *   	&lt;select wicket:id=&quot;site&quot;&gt;
 *   		&lt;option&gt;site 1&lt;/option&gt;
 *   		&lt;option&gt;site 2&lt;/option&gt;
 *   	&lt;/select&gt;
 * </pre>
 * 
 * </p>
 * 
 * <p>
 * You can can extend this class and override method wantOnSelectionChangedNotifications() to force
 * server roundtrips on each selection change.
 * </p>
 * 
 * @author Jonathan Locke
 * @author Eelco Hillenius
 * @author Johan Compagner
 */
public class DropDownChoice extends AbstractSingleSelectChoice implements IOnChangeListener
{
	private static final long serialVersionUID = 1L;

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String)
	 */
	public DropDownChoice(final String id)
	{
		super(id);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, List)
	 */
	public DropDownChoice(final String id, final List choices)
	{
		super(id, choices);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String,
	 *      List,IChoiceRenderer)
	 */
	public DropDownChoice(final String id, final List data, final IChoiceRenderer renderer)
	{
		super(id, data, renderer);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, IModel, List)
	 */
	public DropDownChoice(final String id, IModel model, final List choices)
	{
		super(id, model, choices);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, IModel, List,
	 *      IChoiceRenderer)
	 */
	public DropDownChoice(final String id, IModel model, final List data,
			final IChoiceRenderer renderer)
	{
		super(id, model, data, renderer);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, IModel)
	 */
	public DropDownChoice(String id, IModel choices)
	{
		super(id, choices);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, IModel,IModel)
	 */
	public DropDownChoice(String id, IModel model, IModel choices)
	{
		super(id, model, choices);
	}

	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String,
	 *      IModel,IChoiceRenderer)
	 */
	public DropDownChoice(String id, IModel choices, IChoiceRenderer renderer)
	{
		super(id, choices, renderer);
	}


	/**
	 * @see org.apache.wicket.markup.html.form.AbstractChoice#AbstractChoice(String, IModel,
	 *      IModel,IChoiceRenderer)
	 */
	public DropDownChoice(String id, IModel model, IModel choices, IChoiceRenderer renderer)
	{
		super(id, model, choices, renderer);
	}

	/**
	 * Called when a selection changes.
	 */
	public final void onSelectionChanged()
	{
		convertInput();
		updateModel();
		onSelectionChanged(getModelObject());
	}

	/**
	 * Processes the component tag.
	 * 
	 * @param tag
	 *            Tag to modify
	 * @see org.apache.wicket.Component#onComponentTag(org.apache.wicket.markup.ComponentTag)
	 */
	protected void onComponentTag(final ComponentTag tag)
	{
		checkComponentTag(tag, "select");

		// Should a roundtrip be made (have onSelectionChanged called) when the
		// selection changed?
		if (wantOnSelectionChangedNotifications())
		{
			// url that points to this components IOnChangeListener method
			CharSequence url = urlFor(IOnChangeListener.INTERFACE);

			Form form = (Form)findParent(Form.class);
			if (form != null)
			{
				RequestContext rc = RequestContext.get();
				if (rc.isPortletRequest())
				{
					// restore url back to real wicket path as its going to be interpreted by the
					// form itself
					url = ((PortletRequestContext)rc).getLastEncodedPath();
				}
				tag.put("onchange", form.getJsForInterfaceUrl(url));
			}
			else
			{
				// TODO: following doesn't work with portlets, should be posted to a dynamic hidden
				// form
				// with an ActionURL or something
				tag.put("onchange", "window.location.href='" + url +
						(url.toString().indexOf('?') > -1 ? "&amp;" : "?") + getInputName() +
						"=' + this.options[this.selectedIndex].value;");
			}
		}

		super.onComponentTag(tag);
	}

	/**
	 * Template method that can be overridden by clients that implement IOnChangeListener to be
	 * notified by onChange events of a select element. This method does nothing by default.
	 * <p>
	 * Called when a option is selected of a dropdown list that wants to be notified of this event.
	 * This method is to be implemented by clients that want to be notified of selection events.
	 * 
	 * @param newSelection
	 *            The newly selected object of the backing model NOTE this is the same as you would
	 *            get by calling getModelObject() if the new selection were current
	 */
	protected void onSelectionChanged(final Object newSelection)
	{
	}

	/**
	 * Whether this component's onSelectionChanged event handler should be called using javascript
	 * <tt>window.location</tt> if the selection changes. If true, a roundtrip will be generated
	 * with each selection change, resulting in the model being updated (of just this component) and
	 * onSelectionChanged being called. This method returns false by default. If you wish to use
	 * Ajax instead, let {@link #wantOnSelectionChangedNotifications()} return false and add an
	 * {@link AjaxFormComponentUpdatingBehavior} to the component using the <tt>onchange</tt>
	 * event.
	 * 
	 * @return True if this component's onSelectionChanged event handler should called using
	 *         javascript if the selection changes
	 */
	protected boolean wantOnSelectionChangedNotifications()
	{
		return false;
	}

	/**
	 * @see org.apache.wicket.MarkupContainer#getStatelessHint()
	 */
	protected boolean getStatelessHint()
	{
		if (wantOnSelectionChangedNotifications())
		{
			return false;
		}
		return super.getStatelessHint();
	}
}