关于JAVA如何正确的处理静态文件，数据流的断点续传，查阅许多资料后，还是在tomcat中找到了灵感，具体请参考org.apache.catalina.servlets.DefaultServlet
简单说明下，关于tomcat处理资源请求的主要包括：
1 处理流程在 protected void serveResource(HttpServletRequest request,HttpServletResponse response,boolean content) 中
2 使用缓存进行处理 CacheEntry cacheEntry = resources.lookupCache(path);
3 解析Range的正确方式请参考 // Parse range specifier
765 ranges = parseRange(request, response, cacheEntry.attributes);
766
767 // ETag header
768 response.setHeader("ETag", cacheEntry.attributes.getETag());
769
770 // Last-Modified header
771 response.setHeader("Last-Modified",
772 cacheEntry.attributes.getLastModifiedHttp());
773
774 // Get content length
775 contentLength = cacheEntry.attributes.getContentLength();
776 // Special case for zero length files, which would cause a
777 // (silent) ISE when setting the output buffer size
778 if (contentLength == 0L) {
779 content = false;
780 }
这个方法才是重点 protected Range parseContentRange(HttpServletRequest request,HttpServletResponse response)
经测试，完美支持CHROME,IE,FF,ANDROID,IPAD,IPHONE,SAFARI。
大家可以参考来处理静态资源或是数据流
下面的是整合后的代码，有删改
public String readFile(){ long start = System.currentTimeMillis(); //open virtual dir file in cloud mongodbfile cloudStore = new mongodbfile(); BufferedOutputStream bos = null; String fileId = ""; getResponse().reset(); getResponse().resetBuffer(); int bufferSize = 1024; getResponse().setBufferSize(bufferSize); try { getResponse().setContentType("image/");//请相应修改 getResponse().setHeader("Accept-Ranges", "bytes"); log.debug("readCloudStoreFile fileId = {}",fileId); int readResult = cloudStore.ReadBegin(fileId); if(readResult == 0){//文件读取成功 long contentLength = cloudStore.GetFileLength(fileId); //模拟Etag的信息 getResponse().setHeader("Etag", "W/\""+contentLength+"-1316052976000\""); getResponse().setHeader("Last-Modified", "Thu, 15 Sep 2011 02:16:16 GMT"); byte[] buffer = new byte[bufferSize]; bos = new BufferedOutputStream(getResponse().getOutputStream()); long pos = 0; ArrayList ranges = null; long s = System.currentTimeMillis(); // Parse range specifier ranges = parseRange(request, response, contentLength); long requestLength = 0; if ( (((ranges == null) || (ranges.isEmpty())) && (request.getHeader("Range") == null) ) || (ranges == FULL) ){ if (contentLength < Integer.MAX_VALUE) { getResponse().setContentLength((int) contentLength); } else { // Set the content-length as String to be able to use a long getResponse().setHeader("content-length", "" + contentLength); } requestLength = contentLength; }else{ // 若客户端传来Range，说明之前下载了一部分，设置206状态(SC_PARTIAL_CONTENT) getResponse().setStatus(HttpServletResponse.SC_PARTIAL_CONTENT); log.debug("=======ranges.size() {}",ranges.size()); if (ranges.size() == 1) { Range range = (Range) ranges.get(0); response.addHeader("Content-Range", "bytes " + range.start + "-" + range.end + "/" + range.length); log.debug("Content-Range: {}","bytes " + range.start + "-" + range.end + "/" + range.length); //重点在这里对实时请求的数据长度和数据流剩余长度，和写回Response数据长度的判断 long length = range.end - range.start + 1; if (length < Integer.MAX_VALUE) { response.setContentLength((int) length); } else { // Set the content-length as String to be able to use a long response.setHeader("content-length", "" + length); } log.debug("request range length = {}",length); pos = range.start; requestLength = length; } else { //这里未处理range数组的情况 response.setContentType("multipart/byteranges; boundary=" + mimeSeparation); log.warn("@@@@@@@@@@@ for multipart transfer todo"); } } log.debug("###########skip pos = {}",pos); if (pos != 0) { // 略过已经传输过的字节 long sk = System.currentTimeMillis(); cloudStore.Skip(pos); } long ws = System.currentTimeMillis(); if(requestLength < bufferSize){ bufferSize = (int)requestLength; } int readedLen = 0; for(long len = 0;len<requestLength;){ readedLen = cloudStore.Read(buffer, bufferSize); bos.write(buffer,0,readedLen); len+=readedLen; } bos.flush(); log.debug("write data spent {}",System.currentTimeMillis()-ws); } log.debug("write to response file success fileId = {}",fileId); } catch (Exception e) { }finally{ //关闭资源 return null; } /** * MIME multipart separation string */ protected static final String mimeSeparation = "CATALINA_MIME_BOUNDARY"; /** * Full range marker. */ protected static ArrayList FULL = new ArrayList(); /** * Parse the range header. * * @param request The servlet request we are processing * @param response The servlet response we are creating * @return Vector of ranges */ protected ArrayList parseRange(HttpServletRequest request, HttpServletResponse response,long length) throws IOException { // Checking If-Range String headerValue = request.getHeader("If-Range"); log.debug("headerValue = ",headerValue); if (headerValue != null) { long headerValueTime = (-1L); try { headerValueTime = request.getDateHeader("If-Range"); } catch (IllegalArgumentException e) { ; } String eTag = "W/\""+length+"-1316052976000\""; long lastModified = 1316052976000L; log.debug("headerValueTime = ",headerValueTime); if (headerValueTime == (-1L)) { // If the ETag the client gave does not match the entity // etag, then the entire entity is returned. if (!eTag.equals(headerValue.trim())){ log.debug("If the ETag the client gave does not match the entity etag, " +"then the entire entity is returned."); return FULL; } } else { // If the timestamp of the entity the client got is older than // the last modification date of the entity, the entire entity // is returned. if (lastModified > (headerValueTime + 1000)){ log.debug("If the timestamp of the entity the client got is older " +"than the last modification date of the entity, the entire entity is returned"); return FULL; } } } long fileLength = length; if (fileLength == 0) return null; // Retrieving the range header (if any is specified String rangeHeader = request.getHeader("Range"); log.debug("rangeHeader = ",rangeHeader); if (rangeHeader == null){ return null; } // bytes is the only range unit supported (and I don't see the point // of adding new ones). if (!rangeHeader.startsWith("bytes")) { response.addHeader("Content-Range", "bytes */" + fileLength); response.sendError (HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE); return null; } rangeHeader = rangeHeader.substring(6); // Vector which will contain all the ranges which are successfully // parsed. ArrayList<range> result = new ArrayList</range><range>(); StringTokenizer commaTokenizer = new StringTokenizer(rangeHeader, ","); // Parsing the range list while (commaTokenizer.hasMoreTokens()) { String rangeDefinition = commaTokenizer.nextToken().trim(); Range currentRange = new Range(); currentRange.length = fileLength; int dashPos = rangeDefinition.indexOf('-'); if (dashPos == -1) { response.addHeader("Content-Range", "bytes */" + fileLength); response.sendError (HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE); return null; } if (dashPos == 0) { try { long offset = Long.parseLong(rangeDefinition); currentRange.start = fileLength + offset; currentRange.end = fileLength - 1; } catch (NumberFormatException e) { response.addHeader("Content-Range", "bytes */" + fileLength); response.sendError (HttpServletResponse .SC_REQUESTED_RANGE_NOT_SATISFIABLE); return null; } } else { try { currentRange.start = Long.parseLong (rangeDefinition.substring(0, dashPos)); if (dashPos < rangeDefinition.length() - 1) currentRange.end = Long.parseLong (rangeDefinition.substring (dashPos + 1, rangeDefinition.length())); else currentRange.end = fileLength - 1; } catch (NumberFormatException e) { response.addHeader("Content-Range", "bytes */" + fileLength); response.sendError (HttpServletResponse .SC_REQUESTED_RANGE_NOT_SATISFIABLE); return null; } } if (!currentRange.validate()) { response.addHeader("Content-Range", "bytes */" + fileLength); response.sendError (HttpServletResponse.SC_REQUESTED_RANGE_NOT_SATISFIABLE); return null; } result.add(currentRange); } return result; } // ------------------------------------------------------ Range Inner Class protected class Range { public long start; public long end; public long length; /** * Validate range. */ public boolean validate() { if (end >= length) end = length - 1; return ( (start >= 0) && (end >= 0) && (start < = end) && (length > 0) ); } public void recycle() { start = 0; end = 0; length = 0; } } </range> |
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