/*
* $Id: $
*
* 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.struts.actions;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* This is an abstract base class that minimizes the amount of special coding
* that needs to be written to download a file. All that is required to use
* this class is to extend it and implement the <code>getStreamInfo()</code>
* method so that it returns the relevant information for the file (or other
* stream) to be downloaded. Optionally, the <code>getBufferSize()</code>
* method may be overridden to customize the size of the buffer used to
* transfer the file.
*
* @since Struts 1.2.6
*/
public abstract class DownloadAction extends BaseAction {
/**
* If the <code>getBufferSize()</code> method is not overridden, this is
* the buffer size that will be used to transfer the data to the servlet
* output stream.
*/
protected static final int DEFAULT_BUFFER_SIZE = 4096;
/**
* Returns the information on the file, or other stream, to be downloaded
* by this action. This method must be implemented by an extending class.
*
* @param mapping The ActionMapping used to select this instance.
* @param form The optional ActionForm bean for this request (if
* any).
* @param request The HTTP request we are processing.
* @param response The HTTP response we are creating.
* @return The information for the file to be downloaded.
* @throws Exception if an exception occurs.
*/
protected abstract StreamInfo getStreamInfo(ActionMapping mapping,
ActionForm form, HttpServletRequest request,
HttpServletResponse response)
throws Exception;
/**
* Returns the size of the buffer to be used in transferring the data to
* the servlet output stream. This method may be overridden by an
* extending class in order to customize the buffer size.
*
* @return The size of the transfer buffer, in bytes.
*/
protected int getBufferSize() {
return DEFAULT_BUFFER_SIZE;
}
/**
* Process the specified HTTP request, and create the corresponding HTTP
* response (or forward to another web component that will create it).
* Return an <code>ActionForward</code> instance describing where and how
* control should be forwarded, or <code>null</code> if the response has
* already been completed.
*
* @param mapping The ActionMapping used to select this instance.
* @param form The optional ActionForm bean for this request (if
* any).
* @param request The HTTP request we are processing.
* @param response The HTTP response we are creating.
* @return The forward to which control should be transferred, or
* <code>null</code> if the response has been completed.
* @throws Exception if an exception occurs.
*/
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
StreamInfo info = getStreamInfo(mapping, form, request, response);
String contentType = info.getContentType();
InputStream stream = info.getInputStream();
try {
response.setContentType(contentType);
copy(stream, response.getOutputStream());
} finally {
if (stream != null) {
stream.close();
}
}
// Tell Struts that we are done with the response.
return null;
}
/**
* Copy bytes from an <code>InputStream</code> to an
* <code>OutputStream</code>.
*
* @param input The <code>InputStream</code> to read from.
* @param output The <code>OutputStream</code> to write to.
* @return the number of bytes copied
* @throws IOException In case of an I/O problem
*/
public int copy(InputStream input, OutputStream output)
throws IOException {
byte[] buffer = new byte[getBufferSize()];
int count = 0;
int n = 0;
while (-1 != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
/**
* The information on a file, or other stream, to be downloaded by the
* <code>DownloadAction</code>.
*/
public static interface StreamInfo {
/**
* Returns the content type of the stream to be downloaded.
*
* @return The content type of the stream.
*/
String getContentType();
/**
* Returns an input stream on the content to be downloaded. This
* stream will be closed by the <code>DownloadAction</code>.
*
* @return The input stream for the content to be downloaded.
* @throws IOException if an error occurs
*/
InputStream getInputStream()
throws IOException;
}
/**
* A concrete implementation of the <code>StreamInfo</code> interface
* which simplifies the downloading of a file from the disk.
*/
public static class FileStreamInfo implements StreamInfo {
/**
* The content type for this stream.
*/
private String contentType;
/**
* The file to be downloaded.
*/
private File file;
/**
* Constructs an instance of this class, based on the supplied
* parameters.
*
* @param contentType The content type of the file.
* @param file The file to be downloaded.
*/
public FileStreamInfo(String contentType, File file) {
this.contentType = contentType;
this.file = file;
}
/**
* Returns the content type of the stream to be downloaded.
*
* @return The content type of the stream.
*/
public String getContentType() {
return this.contentType;
}
/**
* Returns an input stream on the file to be downloaded. This stream
* will be closed by the <code>DownloadAction</code>.
*
* @return The input stream for the file to be downloaded.
* @throws IOException if an error occurs
*/
public InputStream getInputStream()
throws IOException {
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
return bis;
}
}
/**
* A concrete implementation of the <code>StreamInfo</code> interface
* which simplifies the downloading of a web application resource.
*/
public static class ResourceStreamInfo implements StreamInfo {
/**
* The content type for this stream.
*/
private String contentType;
/**
* The servlet context for the resource to be downloaded.
*/
private ServletContext context;
/**
* The path to the resource to be downloaded.
*/
private String path;
/**
* Constructs an instance of this class, based on the supplied
* parameters.
*
* @param contentType The content type of the file.
* @param context The servlet context for the resource.
* @param path The path to the resource to be downloaded.
*/
public ResourceStreamInfo(String contentType, ServletContext context,
String path) {
this.contentType = contentType;
this.context = context;
this.path = path;
}
/**
* Returns the content type of the stream to be downloaded.
*
* @return The content type of the stream.
*/
public String getContentType() {
return this.contentType;
}
/**
* Returns an input stream on the resource to be downloaded. This
* stream will be closed by the <code>DownloadAction</code>.
*
* @return The input stream for the resource to be downloaded.
* @throws IOException if an error occurs
*/
public InputStream getInputStream()
throws IOException {
return context.getResourceAsStream(path);
}
}
}