choicerenderer.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 org.apache.wicket.util.lang.PropertyResolver;

/**
 * Default implementation of {@link org.apache.wicket.markup.html.form.IChoiceRenderer}. Usage:
 * <p>
 * 
 * <pre>
 * new DropDownChoice(&quot;users&quot;, new Model(selectedUser), listOfUsers)
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be toString() and the id the index
 * of the object in the ListOfUsers.
 * </p>
 * <p>
 * 
 * <pre>
 * new DropDownChoice(&quot;users&quot;, new Model(selectedUser), listOfUsers, new ChoiceRenderer(&quot;name&quot;))
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be looked up by property expression
 * ("name") and the id the index of the object in the ListOfUsers
 * </p>
 * <p>
 * 
 * <pre>
 * new DropDownChoice(&quot;users&quot;, new Model(selectedUser), listOfUsers, new ChoiceRenderer(&quot;name&quot;, &quot;id&quot;))
 * </pre>
 * 
 * creates a DropDownChoice of users and the display value will be looked up by property expression
 * ("name") and the id will be looked up by the property expression "id"
 * </p>
 * 
 * @author jcompagner
 */
public class ChoiceRenderer implements IChoiceRenderer
{
	private static final long serialVersionUID = 1L;

	/** expression for getting the display value. */
	private final String displayExpression;

	/** expression for getting the id. */
	private final String idExpression;

	/**
	 * Construct. When you use this constructor, the display value will be determined by calling
	 * toString() on the list object, and the id will be based on the list index. the id value will
	 * be the index
	 */
	public ChoiceRenderer()
	{
		super();
		this.displayExpression = null;
		this.idExpression = null;
	}

	/**
	 * Construct. When you use this constructor, the display value will be determined by executing
	 * the given property expression on the list object, and the id will be based on the list index.
	 * The display value will be calculated by the given property expression
	 * 
	 * @param displayExpression
	 *            A property expression to get the display value
	 */
	public ChoiceRenderer(String displayExpression)
	{
		super();
		this.displayExpression = displayExpression;
		this.idExpression = null;
	}

	/**
	 * Construct. When you use this constructor, both the id and the display value will be
	 * determined by executing the given property expressions on the list object.
	 * 
	 * @param displayExpression
	 *            A property expression to get the display value
	 * @param idExpression
	 *            A property expression to get the id value
	 */
	public ChoiceRenderer(String displayExpression, String idExpression)
	{
		super();
		this.displayExpression = displayExpression;
		this.idExpression = idExpression;
	}

	/**
	 * @see org.apache.wicket.markup.html.form.IChoiceRenderer#getDisplayValue(java.lang.Object)
	 */
	public Object getDisplayValue(Object object)
	{
		Object returnValue = object;
		if ((displayExpression != null) && (object != null))
		{
			returnValue = PropertyResolver.getValue(displayExpression, object);
		}

		if (returnValue == null)
		{
			return "";
		}

		return returnValue;
	}

	/**
	 * @see org.apache.wicket.markup.html.form.IChoiceRenderer#getIdValue(java.lang.Object, int)
	 */
	public String getIdValue(Object object, int index)
	{
		if (idExpression == null)
		{
			return Integer.toString(index);
		}

		if (object == null)
		{
			return "";
		}

		Object returnValue = PropertyResolver.getValue(idExpression, object);
		if (returnValue == null)
		{
			return "";
		}

		return returnValue.toString();
	}
}