Java tutorial
package net.dorokhov.pony.web.server.common; /** * net/balusc/webapp/FileServlet.java * * Copyright (C) 2009 BalusC * * This program is free software: you can redistribute it and/or modify it under the terms of the * GNU Lesser General Public License as published by the Free Software Foundation, either version 3 * of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License along with this library. * If not, see . */ import org.springframework.util.StringUtils; import org.springframework.web.servlet.view.AbstractView; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; import java.util.*; /** * LGPL code from http://balusc.blogspot.in/2009/02/fileservlet-supporting-resume-and.html adopted * as Spring View for streaming binary files. * * @author Atul M Dambalkar (Adapted for Spring View) */ public class StreamingViewRenderer extends AbstractView { // Constants ---------------------------------------------------------------------------------- private static final int DEFAULT_BUFFER_SIZE = 20480; // ..bytes = 20KB. private static final long DEFAULT_EXPIRE_TIME = 604800000L; // ..ms = 1 week. private static final String MULTIPART_BOUNDARY = "MULTIPART_BYTERANGES"; @Override protected void renderMergedOutputModel(Map objectMap, HttpServletRequest request, HttpServletResponse response) throws Exception { InputStream dataStream = (InputStream) objectMap.get(DownloadConstants.INPUT_STREAM); if (dataStream == null) { response.sendError(HttpServletResponse.SC_NOT_FOUND); return; } long length = (Long) objectMap.get(DownloadConstants.CONTENT_LENGTH); String fileName = (String) objectMap.get(DownloadConstants.FILENAME); Date lastModifiedObj = (Date) objectMap.get(DownloadConstants.LAST_MODIFIED); if (StringUtils.isEmpty(fileName) || lastModifiedObj == null) { response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR); return; } long lastModified = lastModifiedObj.getTime(); String contentType = (String) objectMap.get(DownloadConstants.CONTENT_TYPE); // Validate request headers for caching --------------------------------------------------- // If-None-Match header should contain "*" or ETag. If so, then return 304. String ifNoneMatch = request.getHeader("If-None-Match"); if (ifNoneMatch != null && matches(ifNoneMatch, fileName)) { response.setHeader("ETag", fileName); // Required in 304. response.sendError(HttpServletResponse.SC_NOT_MODIFIED); return; } // If-Modified-Since header should be greater than LastModified. If so, then return 304. // This header is ignored if any If-None-Match header is specified. long ifModifiedSince = request.getDateHeader("If-Modified-Since"); if (ifNoneMatch == null && ifModifiedSince != -1 && ifModifiedSince + 1000 > lastModified) { response.setHeader("ETag", fileName); // Required in 304. response.sendError(HttpServletResponse.SC_NOT_MODIFIED); return; } // Validate request headers for resume ---------------------------------------------------- // If-Match header should contain "*" or ETag. If not, then return 412. String ifMatch = request.getHeader("If-Match"); if (ifMatch != null && !matches(ifMatch, fileName)) { response.sendError(HttpServletResponse.SC_PRECONDITION_FAILED); return; } // If-Unmodified-Since header should be greater than LastModified. If not, then return 412. long ifUnmodifiedSince = request.getDateHeader("If-Unmodified-Since"); if (ifUnmodifiedSince != -1 && ifUnmodifiedSince + 1000 <= lastModified) { response.sendError(HttpServletResponse.SC_PRECONDITION_FAILED); return; } // Validate and process range ------------------------------------------------------------- // Prepare some variables. The full Range represents the complete file. Range full = new Range(0, length - 1, length); List<Range> ranges = new ArrayList<>(); // Validate and process Range and If-Range headers. String range = request.getHeader("Range"); if (range != null) { // Range header should match format "bytes=n-n,n-n,n-n...". If not, then return 416. if (!range.matches("^bytes=\\d*-\\d*(,\\d*-\\d*)*$")) { response.setHeader("Content-Range", "bytes */" + length); // Required in 416. response.sendError(HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE); return; } String ifRange = request.getHeader("If-Range"); if (ifRange != null && !ifRange.equals(fileName)) { try { long ifRangeTime = request.getDateHeader("If-Range"); // Throws IAE if invalid. if (ifRangeTime != -1) { ranges.add(full); } } catch (IllegalArgumentException ignore) { ranges.add(full); } } // If any valid If-Range header, then process each part of byte range. if (ranges.isEmpty()) { for (String part : range.substring(6).split(",")) { // Assuming a file with length of 100, the following examples returns bytes at: // 50-80 (50 to 80), 40- (40 to length=100), -20 (length-20=80 to length=100). long start = sublong(part, 0, part.indexOf("-")); long end = sublong(part, part.indexOf("-") + 1, part.length()); if (start == -1) { start = length - end; end = length - 1; } else if (end == -1 || end > length - 1) { end = length - 1; } // Check if Range is syntactically valid. If not, then return 416. if (start > end) { response.setHeader("Content-Range", "bytes */" + length); // Required in 416. response.sendError(HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE); return; } // Add range. ranges.add(new Range(start, end, length)); } } } // Prepare and initialize response -------------------------------------------------------- // Get content type by file name and set content disposition. String disposition = "inline"; // If content type is unknown, then set the default value. // For all content types, see: http://www.w3schools.com/media/media_mimeref.asp // To add new content types, add new mime-mapping entry in web.xml. if (contentType == null) { contentType = "application/octet-stream"; } else if (!contentType.startsWith("image")) { // Else, expect for images, determine content disposition. If content type is supported by // the browser, then set to inline, else attachment which will pop a 'save as' dialogue. String accept = request.getHeader("Accept"); disposition = accept != null && accepts(accept, contentType) ? "inline" : "attachment"; } // Initialize response. response.reset(); response.setBufferSize(DEFAULT_BUFFER_SIZE); response.setHeader("Content-Disposition", disposition + ";filename=\"" + fileName + "\""); response.setHeader("Accept-Ranges", "bytes"); response.setHeader("ETag", fileName); response.setDateHeader("Last-Modified", lastModified); response.setDateHeader("Expires", System.currentTimeMillis() + DEFAULT_EXPIRE_TIME); // Send requested file (part(s)) to client ------------------------------------------------ // Prepare streams. InputStream input = null; OutputStream output = null; try { // Open streams. input = new BufferedInputStream(dataStream); output = response.getOutputStream(); if (ranges.isEmpty() || ranges.get(0) == full) { // Return full file. response.setContentType(contentType); response.setHeader("Content-Range", "bytes " + full.start + "-" + full.end + "/" + full.total); response.setHeader("Content-Length", String.valueOf(full.length)); copy(input, output, length, full.start, full.length); } else if (ranges.size() == 1) { // Return single part of file. Range r = ranges.get(0); response.setContentType(contentType); response.setHeader("Content-Range", "bytes " + r.start + "-" + r.end + "/" + r.total); response.setHeader("Content-Length", String.valueOf(r.length)); response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT); // 206. // Copy single part range. copy(input, output, length, r.start, r.length); } else { // Return multiple parts of file. response.setContentType("multipart/byteranges; boundary=" + MULTIPART_BOUNDARY); response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT); // 206. // Cast back to ServletOutputStream to get the easy println methods. ServletOutputStream sos = (ServletOutputStream) output; // Copy multi part range. for (Range r : ranges) { // Add multipart boundary and header fields for every range. sos.println(); sos.println("--" + MULTIPART_BOUNDARY); sos.println("Content-Type: " + contentType); sos.println("Content-Range: bytes " + r.start + "-" + r.end + "/" + r.total); // Copy single part range of multi part range. copy(input, output, length, r.start, r.length); } // End with multipart boundary. sos.println(); sos.println("--" + MULTIPART_BOUNDARY + "--"); } } finally { // Gently close streams. close(output); close(input); close(dataStream); } } /** * Close the given resource. * @param resource The resource to be closed. */ private static void close(Closeable resource) { if (resource != null) { try { resource.close(); } catch (IOException ignore) { // Ignore IOException. If you want to handle this anyway, it might be useful to know // that this will generally only be thrown when the client aborted the request. } } } /** * Copy the given byte range of the given input to the given output. * @param input The input to copy the given range to the given output for. * @param output The output to copy the given range from the given input for. * @param start Start of the byte range. * @param length Length of the byte range. * @throws IOException If something fails at I/O level. */ private static void copy(InputStream input, OutputStream output, long inputSize, long start, long length) throws IOException { byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; int read; if (inputSize == length) { // Write full range. while ((read = input.read(buffer)) > 0) { output.write(buffer, 0, read); output.flush(); } } else { //noinspection ResultOfMethodCallIgnored input.skip(start); long toRead = length; while ((read = input.read(buffer)) > 0) { if ((toRead -= read) > 0) { output.write(buffer, 0, read); output.flush(); } else { output.write(buffer, 0, (int) toRead + read); output.flush(); break; } } } } /** * Returns true if the given accept header accepts the given value. * @param acceptHeader The accept header. * @param toAccept The value to be accepted. * @return 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; } /** * Returns true if the given match header matches the given value. * @param matchHeader The match header. * @param toMatch The value to be matched. * @return True if the given match header matches the given value. */ private static boolean matches(String matchHeader, String toMatch) { String[] matchValues = matchHeader.split("\\s*,\\s*"); Arrays.sort(matchValues); return Arrays.binarySearch(matchValues, toMatch) > -1 || Arrays.binarySearch(matchValues, "*") > -1; } /** * 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 * @param value The string value to return a substring as long for. * @param beginIndex The begin index of the substring to be returned as long. * @param endIndex The end index of the substring to be returned as long. * @return A substring of the given string value as long or -1 if substring is empty. */ private static long sublong(String value, int beginIndex, int endIndex) { String substring = value.substring(beginIndex, endIndex); return (substring.length() > 0) ? Long.parseLong(substring) : -1; } // Inner classes ------------------------------------------------------------------------------ /** * This class represents a byte range. */ protected class Range { long start; long end; long length; long total; /** * Construct a byte range. * @param start Start of the byte range. * @param end End of the byte range. * @param total Total length of the byte source. */ public Range(long start, long end, long total) { this.start = start; this.end = end; this.length = end - start + 1; this.total = total; } } public class DownloadConstants { public static final String INPUT_STREAM = "inputStream"; public static final String CONTENT_TYPE = "contentType"; public static final String CONTENT_LENGTH = "contentLength"; public static final String FILENAME = "filename"; public static final String LAST_MODIFIED = "lastModified"; } }