button.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.markup.ComponentTag;
import org.apache.wicket.model.IModel;
import org.apache.wicket.version.undo.Change;

/**
 * A form button.
 * <p>
 * Within a form, you can nest Button components. Note that you don't have to do this to let the
 * form work (a simple &lt;input type="submit".. suffices), but if you want to have different kinds
 * of submit behavior it might be a good idea to use Buttons.
 * </p>
 * <p>
 * The model property is used to set the &quot;value&quot; attribute. It will thus be the label of
 * the button that shows up for end users. If you want the attribute to keep it's markup attribute
 * value, don't provide a model, or let it return an empty string.
 * </p>
 * <p>
 * When you add a Wicket Button to a form, and that button is clicked, by default the button's
 * onSubmit method is called first, and after that the form's onSubmit method is called. If you want
 * to change this (e.g. you don't want to call the form's onSubmit method, or you want it called
 * before the button's onSubmit method), you can override Form.delegateSubmit.
 * </p>
 * <p>
 * One other option you should know of is the 'defaultFormProcessing' property of Button components.
 * When you set this to false (default is true), all validation and formupdating is bypassed and the
 * onSubmit method of that button is called directly, and the onSubmit method of the parent form is
 * not called. A common use for this is to create a cancel button.
 * </p>
 * 
 * @author Jonathan Locke
 * @author Eelco Hillenius
 */
public class Button extends FormComponent implements IFormSubmittingComponent
{
	private static final long serialVersionUID = 1L;

	/**
	 * If false, all standard processing like validating and model updating is skipped.
	 */
	private boolean defaultFormProcessing = true;

	/**
	 * Constructor without a model. Buttons without models leave the markup attribute
	 * &quot;value&quot;. Provide a model if you want to set the button's label dynamically.
	 * 
	 * @see org.apache.wicket.Component#Component(String)
	 */
	public Button(String id)
	{
		super(id);
		setVersioned(true);
		setOutputMarkupId(true);
	}

	/**
	 * Constructor taking an model for rendering the 'label' of the button (the value attribute of
	 * the input/button tag). Use a {@link org.apache.wicket.model.StringResourceModel} for a
	 * localized value.
	 * 
	 * @param id
	 *            Component id
	 * @param model
	 *            The model property is used to set the &quot;value&quot; attribute. It will thus be
	 *            the label of the button that shows up for end users. If you want the attribute to
	 *            keep it's markup attribute value, don't provide a model, or let it return an empty
	 *            string.
	 */
	public Button(final String id, final IModel model)
	{
		super(id, model);
		setVersioned(true);
		setOutputMarkupId(true);
	}

	/**
	 * Override of the default initModel behaviour. This component <strong>will not</strong> use
	 * any compound model a parent, but only a model that is explicitly set.
	 * 
	 * @see org.apache.wicket.Component#initModel()
	 */
	protected IModel initModel()
	{
		return null;
	}

	/**
	 * Gets the defaultFormProcessing property. When false (default is true), all validation and
	 * formupdating is bypassed and the onSubmit method of that button is called directly, and the
	 * onSubmit method of the parent form is not called. A common use for this is to create a cancel
	 * button.
	 * 
	 * @return defaultFormProcessing
	 */
	public final boolean getDefaultFormProcessing()
	{
		return defaultFormProcessing;
	}

	/**
	 * Sets the defaultFormProcessing property. When false (default is true), all validation and
	 * form updating is bypassed and the onSubmit method of that button is called directly, and the
	 * onSubmit method of the parent form is not called. A common use for this is to create a cancel
	 * button.
	 * 
	 * @param defaultFormProcessing
	 *            defaultFormProcessing
	 * @return This
	 */
	public final Button setDefaultFormProcessing(boolean defaultFormProcessing)
	{
		if (this.defaultFormProcessing != defaultFormProcessing)
		{
			addStateChange(new Change()
			{
				private static final long serialVersionUID = 1L;

				boolean formerValue = Button.this.defaultFormProcessing;

				public void undo()
				{
					Button.this.defaultFormProcessing = formerValue;
				}

				public String toString()
				{
					return "DefaultFormProcessingChange[component: " + getPath() +
							", default processing: " + formerValue + "]";
				}
			});
		}

		this.defaultFormProcessing = defaultFormProcessing;
		return this;
	}

	/**
	 * This method does nothing, as any model of a button is only used to display the button's label
	 * (by setting it's markup attribute &quot;value&quot;).
	 * 
	 * @see org.apache.wicket.markup.html.form.FormComponent#updateModel()
	 */
	public void updateModel()
	{
	}

	/**
	 * Gets any script that should rendered as the &quot;onclick&quot; attribute of the button.
	 * Returns null by default, override this method to provide any script.
	 * 
	 * @return Any onClick JavaScript that should be used, returns null by default
	 */
	protected String getOnClickScript()
	{
		return null;
	}

	/**
	 * Processes the component tag. A <tt>value</tt> attribute is added with the value of the
	 * model object, if available. An <tt>onclick</tt> attribute is added if the subclass
	 * specified javascript.
	 * 
	 * <p>
	 * <b>NOTE</b>. For a <tt>&lt;button&gt;</tt> the <tt>value</tt> attribute is not rendered,
	 * markup needs to be added within the button to display the button's label.
	 * </p>
	 * 
	 * @param tag
	 *            Tag to modify
	 * @see org.apache.wicket.Component#onComponentTag(ComponentTag)
	 */
	protected void onComponentTag(final ComponentTag tag)
	{
		// Default handling for component tag
		super.onComponentTag(tag);

		try
		{
			String value = getModelObjectAsString();
			if (value != null && !"".equals(value))
			{
				tag.put("value", value);
			}
		}
		catch (Exception e)
		{
			// ignore.
		}

		// If the subclass specified javascript, use that
		final String onClickJavaScript = getOnClickScript();
		if (onClickJavaScript != null)
		{
			tag.put("onclick", onClickJavaScript);
		}
	}

	/**
	 * Override this method to provide special submit handling in a multi-button form. It is called
	 * whenever the user clicks this particular button.
	 */
	public void onSubmit()
	{
	}
}