downloadlink.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.link;

import java.io.File;

import org.apache.wicket.RequestCycle;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.apache.wicket.request.target.resource.ResourceStreamRequestTarget;
import org.apache.wicket.util.resource.FileResourceStream;
import org.apache.wicket.util.resource.IResourceStream;
import org.apache.wicket.util.string.Strings;


/**
 * A link that streams a file to the client. When clicked this link will prompt the save as dialog
 * in the browser.
 * 
 * NOTICE that this link will block the pagemap. That means only one link from the pagemap can be
 * downloaded at a time, and also while the download happens no pages from this pagemap can be
 * accessed. If you need to stream multiple files concurrently without blocking then you should use
 * shared resources or a non-wicket servlet.
 * 
 * @author Igor Vaynberg (ivaynberg)
 */
public class DownloadLink extends Link
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * File name to stream
	 */
	private String fileName;

	private boolean deleteAfter;


	/**
	 * Constructor. File name used will be the result of <code>file.getName()</code>
	 * 
	 * @param id
	 *            component id
	 * @param file
	 *            file to stream to client
	 */
	public DownloadLink(String id, File file)
	{
		super(id);
		if (file == null)
		{
			throw new IllegalArgumentException("file cannot be null");
		}
		setModel(new Model(file));
	}

	/**
	 * Constructor. File name used will be the result of <code>file.getName()</code>
	 * 
	 * @param id
	 *            component id
	 * @param model
	 *            model that contains the file object
	 */
	public DownloadLink(String id, IModel model)
	{
		super(id, model);
	}

	/**
	 * Constructor. File name used will be the result of <code>file.getName()</code>
	 * 
	 * @param id
	 *            component id
	 * @param model
	 *            model that contains the file object
	 * @param fileName
	 *            name of the file
	 */
	public DownloadLink(String id, IModel model, String fileName)
	{
		super(id, model);
		this.fileName = fileName;
	}


	/**
	 * Constructor
	 * 
	 * @param id
	 *            component id
	 * @param file
	 *            file to stream to client
	 * @param fileName
	 *            name of the file
	 */
	public DownloadLink(String id, File file, String fileName)
	{
		super(id);
		if (file == null)
		{
			throw new IllegalArgumentException("file cannot be null");
		}
		if (Strings.isEmpty(fileName))
		{
			throw new IllegalArgumentException("fileName cannot be an empty string");
		}
		setModel(new Model(file));
		this.fileName = fileName;
	}


	/**
	 * 
	 * @see org.apache.wicket.markup.html.link.Link#onClick()
	 */
	public void onClick()
	{
		final File file = (File)getModelObject();
		if (file == null)
		{
			throw new IllegalStateException(getClass().getName() +
					" failed to retrieve a File object from model");
		}
		final String fn = (fileName != null) ? fileName : file.getName();

		IResourceStream resourceStream = new FileResourceStream(
				new org.apache.wicket.util.file.File(file));
		getRequestCycle().setRequestTarget(new ResourceStreamRequestTarget(resourceStream)
		{
			public String getFileName()
			{
				return fn;
			}

			public void respond(RequestCycle requestCycle)
			{
				super.respond(requestCycle);

				if (deleteAfter)
					file.delete();
			}
		});
	}

	/**
	 * USE THIS METHOD WITH CAUTION!
	 * 
	 * If true, the file will be deleted! The recommended way to use this setting, is to set this
	 * DownloadLink object's model with a LoadableDetachableModel instance and the resulting file
	 * being generated in a temporary folder.
	 * 
	 * @param deleteAfter
	 *            true to delete file after download succeeds
	 * @return component
	 */
	public final DownloadLink setDeleteAfterDownload(boolean deleteAfter)
	{
		this.deleteAfter = deleteAfter;

		return this;
	}
}