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improved FileServlet

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This commit is contained in:
Walter Oggioni
2016-07-06 23:03:19 +02:00
parent 3385cafc32
commit 63794fff53
2 changed files with 660 additions and 34 deletions
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656
src/main/java/org/jpacrepo/frontend/servlet/AbstractFileServlet.java Normal file
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@@ -0,0 +1,656 @@
package org.jpacrepo.frontend.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import java.util.regex.Pattern;
import static java.nio.charset.StandardCharsets.UTF_8;
/**
* <p>
* The well known "<a href="http://balusc.omnifaces.org/2009/02/fileservlet-supporting-resume-and.html">BalusC FileServlet</a>",
* as an abstract template, slightly refactored, rewritten and modernized with a.o. fast NIO stuff instead of legacy
* RandomAccessFile.
* <p>
* This servlet properly deals with <code>ETag</code>, <code>If-None-Match</code> and <code>If-Modified-Since</code>
* caching requests, hereby improving browser caching. This servlet also properly deals with <code>Range</code> and
* <code>If-Range</code> ranging requests (<a href="https://tools.ietf.org/html/rfc7233">RFC7233</a>), which is required
* by most media players for proper audio/video streaming, and by webbrowsers and for a proper resume of an paused
* download, and by download accelerators to be able to request smaller parts simultaneously. This servlet is ideal when
* you have large files like media files placed outside the web application and you can't use the default servlet.
* <p>
* <h3>Usage</h3>
* <p>
* Just extend this class and override the {@link #getFile(HttpServletRequest)} method to return the desired file. If
* you want to trigger a HTTP 400 "Bad Request" error, simply throw {@link IllegalArgumentException}. If you want to
* trigger a HTTP 404 "Not Found" error, simply return <code>null</code>, or a non-existent file.
* <p>
* Here's a concrete example which serves it via an URL like <code>/media/foo.ext</code>:
* <p>
* <pre>
* &#64;WebServlet("/media/*")
* public class MediaFileServlet extends FileServlet {
*
* private File folder;
*
* &#64;Override
* public void init() throws ServletException {
* folder = new File("/var/webapp/media");
* }
*
* &#64;Override
* protected File getFile(HttpServletRequest request) throws IllegalArgumentException {
* String pathInfo = request.getPathInfo();
*
* if (pathInfo == null || pathInfo.isEmpty() || "/".equals(pathInfo)) {
* throw new IllegalArgumentException();
* }
*
* return new File(folder, pathInfo);
* }
*
* }
* </pre>
* <p>
* You can embed it in e.g. HTML5 video tag as below:
* <pre>
* &lt;video src="#{request.contextPath}/media/video.mp4" controls="controls" /&gt;
* </pre>
* <p>
* <h3>Customizing <code>FileServlet</code></h3>
* <p>
* If more fine grained control is desired for handling "file not found" error, determining the cache expire time, the
* content type, whether the file should be supplied as an attachment and the attachment's file name, then the developer
* can opt to override one or more of the following protected methods:
* <ul>
* <li>{@link #handleFileNotFound(HttpServletRequest, HttpServletResponse)}
* <li>{@link #getExpireTime(HttpServletRequest, File)}
* <li>{@link #getContentType(HttpServletRequest, File)}
* <li>{@link #isAttachment(HttpServletRequest, String)}
* <li>{@link #getAttachmentName(HttpServletRequest, File)}
* </ul>
* <p>
* <p><strong>See also</strong>:
* <ul>
* <li><a href="http://stackoverflow.com/q/13588149/157882">How to stream audio/video files such as MP3, MP4, AVI, etc using a Servlet</a>
* <li><a href="http://stackoverflow.com/a/29991447/157882">Abstract template for a static resource servlet</a>
* </ul>
*
* @author Bauke Scholtz
* @since 2.2
*/
public abstract class AbstractFileServlet extends HttpServlet
{
// Constants ------------------------------------------------------------------------------------------------------
private static final long serialVersionUID = 1L;
private static final int DEFAULT_STREAM_BUFFER_SIZE = 10240;
private static final String ERROR_UNSUPPORTED_ENCODING = "UTF-8 is apparently not supported on this platform.";
private static final Long DEFAULT_EXPIRE_TIME_IN_SECONDS = TimeUnit.DAYS.toSeconds(30);
private static final long ONE_SECOND_IN_MILLIS = TimeUnit.SECONDS.toMillis(1);
private static final String ETAG = "W/\"%s-%s\"";
private static final Pattern RANGE_PATTERN = Pattern.compile("^bytes=[0-9]*-[0-9]*(,[0-9]*-[0-9]*)*$");
private static final String CONTENT_DISPOSITION_HEADER = "%s;filename=\"%2$s\"; filename*=UTF-8''%2$s";
private static final String MULTIPART_BOUNDARY = UUID.randomUUID().toString();
private static long stream(InputStream input, OutputStream output) throws IOException
{
try (ReadableByteChannel inputChannel = Channels.newChannel(input);
WritableByteChannel outputChannel = Channels.newChannel(output))
{
ByteBuffer buffer = ByteBuffer.allocateDirect(DEFAULT_STREAM_BUFFER_SIZE);
long size = 0;
while (inputChannel.read(buffer) != -1)
{
buffer.flip();
size += outputChannel.write(buffer);
buffer.clear();
}
return size;
}
}
/**
* Stream a specified range of the given file to the given output via NIO {@link Channels} and a directly allocated
* NIO {@link ByteBuffer}. The output stream will only implicitly be closed after streaming when the specified range
* represents the whole file, regardless of whether an exception is been thrown or not.
*
* @param file The file.
* @param output The output stream.
* @param start The start position (offset).
* @param length The (intented) length of written bytes.
* @return The (actual) length of the written bytes. This may be smaller when the given length is too large.
* @throws IOException When an I/O error occurs.
* @since 2.2
*/
public static long stream(File file, OutputStream output, long start, long length) throws IOException
{
if (start == 0 && length >= file.length())
{
return stream(new FileInputStream(file), output);
}
try (FileChannel fileChannel = (FileChannel) Files.newByteChannel(file.toPath(), StandardOpenOption.READ))
{
WritableByteChannel outputChannel = Channels.newChannel(output);
ByteBuffer buffer = ByteBuffer.allocateDirect(DEFAULT_STREAM_BUFFER_SIZE);
long size = 0;
while (fileChannel.read(buffer, start + size) != -1)
{
buffer.flip();
if (size + buffer.limit() > length)
{
buffer.limit((int) (length - size));
}
size += outputChannel.write(buffer);
if (size >= length)
{
break;
}
buffer.clear();
}
return size;
}
}
private static String encodeURL(String string)
{
if (string == null)
{
return null;
}
try
{
return URLEncoder.encode(string, UTF_8.name());
}
catch (UnsupportedEncodingException e)
{
throw new UnsupportedOperationException(ERROR_UNSUPPORTED_ENCODING, e);
}
}
private static String encodeURI(String string)
{
if (string == null)
{
return null;
}
return encodeURL(string)
.replace("+", "%20")
.replace("%21", "!")
.replace("%27", "'")
.replace("%28", "(")
.replace("%29", ")")
.replace("%7E", "~");
}
// Actions --------------------------------------------------------------------------------------------------------
@Override
protected void doHead(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doRequest(request, response, true);
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doRequest(request, response, false);
}
private void doRequest(HttpServletRequest request, HttpServletResponse response, boolean head) throws IOException
{
response.reset();
Resource resource;
try
{
resource = new Resource(getFile(request));
}
catch (IllegalArgumentException e)
{
response.sendError(HttpServletResponse.SC_BAD_REQUEST);
return;
}
if (resource.file == null)
{
handleFileNotFound(request, response);
return;
}
if (preconditionFailed(request, resource))
{
response.sendError(HttpServletResponse.SC_PRECONDITION_FAILED);
return;
}
setCacheHeaders(response, resource, getExpireTime(request, resource.file));
if (notModified(request, resource))
{
response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
return;
}
List<Range> ranges = getRanges(request, resource);
if (ranges == null)
{
response.setHeader("Content-Range", "bytes */" + resource.length);
response.sendError(HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE);
return;
}
if (!ranges.isEmpty())
{
response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
}
else
{
ranges.add(new Range(0, resource.length - 1)); // Full content.
}
String contentType = setContentHeaders(request, response, resource, ranges);
if (head)
{
return;
}
writeContent(response, resource, ranges, contentType);
}
/**
* Returns the file associated with the given HTTP servlet request.
* If this method throws {@link IllegalArgumentException}, then the servlet will return a HTTP 400 error.
* If this method returns <code>null</code>, or if {@link File#isFile()} returns <code>false</code>, then the
* servlet will invoke {@link #handleFileNotFound(HttpServletRequest, HttpServletResponse)}.
*
* @param request The involved HTTP servlet request.
* @return The file associated with the given HTTP servlet request.
* @throws IllegalArgumentException When the request is mangled in such way that it's not recognizable as a valid
* file request. The servlet will then return a HTTP 400 error.
*/
protected abstract File getFile(HttpServletRequest request) throws IllegalArgumentException;
/**
* Handles the case when the file is not found.
* <p>
* The default implementation sends a HTTP 404 error.
*
* @param request The involved HTTP servlet request.
* @param response The involved HTTP servlet response.
* @throws IOException When something fails at I/O level.
* @since 2.3
*/
protected void handleFileNotFound(HttpServletRequest request, HttpServletResponse response) throws IOException
{
response.sendError(HttpServletResponse.SC_NOT_FOUND);
}
/**
* Returns how long the resource may be cached by the client before it expires, in seconds.
* <p>
* The default implementation returns 30 days in seconds.
*
* @param request The involved HTTP servlet request.
* @param file The involved file.
* @return The client cache expire time in seconds (not milliseconds!).
*/
protected long getExpireTime(HttpServletRequest request, File file)
{
return DEFAULT_EXPIRE_TIME_IN_SECONDS;
}
/**
* Returns the content type associated with the given HTTP servlet request and file.
* <p>
* The default implementation delegates {@link File#getName()} to {@link ServletContext#getMimeType(String)} with a
* fallback default value of <code>application/octet-stream</code>.
*
* @param request The involved HTTP servlet request.
* @param file The involved file.
* @return The content type associated with the given HTTP servlet request and file.
*/
protected String getContentType(HttpServletRequest request, File file)
{
String type = request.getServletContext().getMimeType(file.getName());
if (type != null)
{
return type;
}
else
{
return "application/octet-stream";
}
}
/**
* Returns <code>true</code> if we must force a "Save As" dialog based on the given HTTP servlet request and content
* type as obtained from {@link #getContentType(HttpServletRequest, File)}.
* <p>
* The default implementation will return <code>true</code> if the content type does <strong>not</strong> start with
* <code>text</code> or <code>image</code>, and the <code>Accept</code> request header is either <code>null</code>
* or does not match the given content type.
*
* @param request The involved HTTP servlet request.
* @param contentType The content type of the involved file.
* @return <code>true</code> if we must force a "Save As" dialog based on the given HTTP servlet request and content
* type.
*/
protected boolean isAttachment(HttpServletRequest request, String contentType)
{
String accept = request.getHeader("Accept");
return (!contentType.startsWith("text") && !contentType.startsWith("image")) && (accept == null || !accepts(accept, contentType));
}
/**
* Returns the file name to be used in <code>Content-Disposition</code> header.
* This does not need to be URL-encoded as this will be taken care of.
* <p>
* The default implementation returns {@link File#getName()}.
*
* @param request The involved HTTP servlet request.
* @param file The involved file.
* @return The file name to be used in <code>Content-Disposition</code> header.
* @since 2.3
*/
protected String getAttachmentName(HttpServletRequest request, File file)
{
return file.getName();
}
// Sub-actions ----------------------------------------------------------------------------------------------------
/**
* Returns true if it's a conditional request which must return 412.
*/
private boolean preconditionFailed(HttpServletRequest request, Resource resource)
{
String match = request.getHeader("If-Match");
long unmodified = request.getDateHeader("If-Unmodified-Since");
return (match != null) ? !matches(match, resource.eTag) : (unmodified != -1 && modified(unmodified, resource.lastModified));
}
/**
* Set cache headers.
*/
private void setCacheHeaders(HttpServletResponse response, Resource resource, long expires)
{
//Servlets.setCacheHeaders(response, expires);
response.setHeader("ETag", resource.eTag);
response.setDateHeader("Last-Modified", resource.lastModified);
}
/**
* Returns true if it's a conditional request which must return 304.
*/
private boolean notModified(HttpServletRequest request, Resource resource)
{
String noMatch = request.getHeader("If-None-Match");
long modified = request.getDateHeader("If-Modified-Since");
return (noMatch != null) ? matches(noMatch, resource.eTag) : (modified != -1 && !modified(modified, resource.lastModified));
}
/**
* Get requested ranges. If this is null, then we must return 416. If this is empty, then we must return full file.
*/
private List<Range> getRanges(HttpServletRequest request, Resource resource)
{
List<Range> ranges = new ArrayList<>(1);
String rangeHeader = request.getHeader("Range");
if (rangeHeader == null)
{
return ranges;
}
else if (!RANGE_PATTERN.matcher(rangeHeader).matches())
{
return null; // Syntax error.
}
String ifRange = request.getHeader("If-Range");
if (ifRange != null && !ifRange.equals(resource.eTag))
{
try
{
long ifRangeTime = request.getDateHeader("If-Range");
if (ifRangeTime != -1 && modified(ifRangeTime, resource.lastModified))
{
return ranges;
}
}
catch (IllegalArgumentException ifRangeHeaderIsInvalid)
{
return ranges;
}
}
for (String rangeHeaderPart : rangeHeader.split("=")[1].split(","))
{
Range range = parseRange(rangeHeaderPart, resource.length);
if (range == null)
{
return null; // Logic error.
}
ranges.add(range);
}
return ranges;
}
/**
* Parse range header part. Returns null if there's a logic error (i.e. start after end).
*/
private Range parseRange(String range, long length)
{
long start = sublong(range, 0, range.indexOf('-'));
long end = sublong(range, range.indexOf('-') + 1, range.length());
if (start == -1)
{
start = length - end;
end = length - 1;
}
else if (end == -1 || end > length - 1)
{
end = length - 1;
}
if (start > end)
{
return null; // Logic error.
}
return new Range(start, end);
}
/**
* Set content headers.
*/
private String setContentHeaders(HttpServletRequest request, HttpServletResponse response, Resource resource, List<Range> ranges)
{
String contentType = getContentType(request, resource.file);
String disposition = isAttachment(request, contentType) ? "attachment" : "inline";
String filename = encodeURI(getAttachmentName(request, resource.file));
response.setHeader("Content-Disposition", String.format(CONTENT_DISPOSITION_HEADER, disposition, filename));
response.setHeader("Accept-Ranges", "bytes");
if (ranges.size() == 1)
{
Range range = ranges.get(0);
response.setContentType(contentType);
response.setHeader("Content-Length", String.valueOf(range.length));
if (response.getStatus() == HttpServletResponse.SC_PARTIAL_CONTENT)
{
response.setHeader("Content-Range", "bytes " + range.start + "-" + range.end + "/" + resource.length);
}
}
else
{
response.setContentType("multipart/byteranges; boundary=" + MULTIPART_BOUNDARY);
}
return contentType;
}
/**
* Write given file to response with given content type and ranges.
*/
private void writeContent(HttpServletResponse response, Resource resource, List<Range> ranges, String contentType) throws IOException
{
ServletOutputStream output = response.getOutputStream();
if (ranges.size() == 1)
{
Range range = ranges.get(0);
stream(resource.file, output, range.start, range.length);
}
else
{
for (Range range : ranges)
{
output.println();
output.println("--" + MULTIPART_BOUNDARY);
output.println("Content-Type: " + contentType);
output.println("Content-Range: bytes " + range.start + "-" + range.end + "/" + resource.length);
stream(resource.file, output, range.start, range.length);
}
output.println();
output.println("--" + MULTIPART_BOUNDARY + "--");
}
}
// Helpers --------------------------------------------------------------------------------------------------------
/**
* Returns true if the given match header matches the given ETag value.
*/
private static boolean matches(String matchHeader, String eTag)
{
String[] matchValues = matchHeader.split("\\s*,\\s*");
Arrays.sort(matchValues);
return Arrays.binarySearch(matchValues, eTag) > -1
|| Arrays.binarySearch(matchValues, "*") > -1;
}
/**
* Returns true if the given modified header is older than the given last modified value.
*/
private static boolean modified(long modifiedHeader, long lastModified)
{
return (modifiedHeader + ONE_SECOND_IN_MILLIS <= lastModified); // That second is because the header is in seconds, not millis.
}
/**
* Returns a substring of the given string value from the given begin index to the given end index as a long.
* If the substring is empty, then -1 will be returned.
*/
private static long sublong(String value, int beginIndex, int endIndex)
{
String substring = value.substring(beginIndex, endIndex);
return substring.isEmpty() ? -1 : Long.parseLong(substring);
}
/**
* Returns true if the given accept header accepts the given value.
*/
private static boolean accepts(String acceptHeader, String toAccept)
{
String[] acceptValues = acceptHeader.split("\\s*(,|;)\\s*");
Arrays.sort(acceptValues);
return Arrays.binarySearch(acceptValues, toAccept) > -1
|| Arrays.binarySearch(acceptValues, toAccept.replaceAll("/.*$", "/*")) > -1
|| Arrays.binarySearch(acceptValues, "*/*") > -1;
}
// Nested classes -------------------------------------------------------------------------------------------------
/**
* Convenience class for a file resource.
*/
private static class Resource
{
private final File file;
private final long length;
private final long lastModified;
private final String eTag;
public Resource(File file)
{
if (file != null && file.isFile())
{
this.file = file;
length = file.length();
lastModified = file.lastModified();
eTag = String.format(ETAG, encodeURL(file.getName()), lastModified);
}
else
{
this.file = null;
length = 0;
lastModified = 0;
eTag = null;
}
}
}
/**
* Convenience class for a byte range.
*/
private static class Range
{
private final long start;
private final long end;
private final long length;
public Range(long start, long end)
{
this.start = start;
this.end = end;
length = end - start + 1;
}
}
}

38
src/main/java/org/jpacrepo/frontend/servlet/FileServlet.java
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@@ -23,46 +23,16 @@ import java.util.logging.Logger;
@WebServlet("/archive/*")
public class FileServlet extends HttpServlet
public class FileServlet extends AbstractFileServlet
{
@Inject
@DefaultConfiguration
private ApplicationContext ctx;
private Logger log = Logger.getLogger(FileServlet.class.getName());
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
@Override
protected File getFile(HttpServletRequest request) throws IllegalArgumentException
{
String fileName = request.getPathInfo().substring(1);
if (fileName == null || fileName.equals(""))
{
throw new ServletException("File Name can't be null or empty");
}
File file = new File(ctx.getSystemProperties().getProperty("RepoFolder"), fileName);
if (!file.exists())
{
response.sendError(HttpServletResponse.SC_NOT_FOUND);
//response.sendRedirect("../404.xhtml");
return;
}
log.fine("File location on server::" + file.getAbsolutePath());
ServletContext ctx = getServletContext();
InputStream fis = new FileInputStream(file);
String mimeType = ctx.getMimeType(file.getAbsolutePath());
response.setContentType(mimeType != null ? mimeType : "application/octet-stream");
response.setContentLength((int) file.length());
response.setHeader("Content-Disposition", String.format("attachment; filename=\"%s\"", fileName));
ServletOutputStream os = response.getOutputStream();
byte[] bufferData = new byte[1024];
int read;
while ((read = fis.read(bufferData)) != -1)
{
os.write(bufferData, 0, read);
}
os.close();
fis.close();
log.fine("File successfully downloaded to client");
return new File(ctx.getSystemProperties().getProperty("RepoFolder"), request.getPathInfo().substring(1));
}
}