Java 服务器端支持断点续传的源代码

Java 服务器端支持断点续传的源代码【支持快车、迅雷】（仅支持 HTTP 协议）

网上关于 Java 支持 HTTP 断点续传的文章不少，但关于 Java 服务器端支持 HTTP 断点续传的却比较少。
本文是 Java 服务器端支持 HTTP 断点续传的源代码，支持快车、迅雷。
本文使用一个简单的 Servlet 来作为支持断点续传的下载示例，在 Java Web 项目下部署好后，可以使用诸如 http://localhost/cds/http 的链接来调用 Servlet，进而被快车/迅雷监听进行下载。

ArcSyncHttpDownloadServlet 源代码：  [java] view plaincopyprint?  package com.defonds.cds.common;    import java.io.BufferedOutputStream;  import java.io.File;  import java.io.IOException;  import java.io.OutputStream;  import java.io.RandomAccessFile;    import javax.servlet.ServletException;  import javax.servlet.http.HttpServlet;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;    import org.apache.commons.logging.Log;  import org.apache.commons.logging.LogFactory;    import com.defonds.cds.common.util.CommonUtil;    //HTTP 断点续传 demo（客户端测试工具：快车、迅雷）  public class ArcSyncHttpDownloadServlet extends HttpServlet {  private static final long serialVersionUID = 1L;  final static Log log = LogFactory.getLog(ArcSyncHttpDownloadServlet.class);    @Override  protected void doGet(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, IOException {  this.doPost(req, resp);  }    @Override  protected void doPost(HttpServletRequest request, HttpServletResponse response) {  File downloadFile = new File("D:/defonds/book/pattern/SteveJobsZH.pdf");//要下载的文件  long fileLength = downloadFile.length();//记录文件大小  long pastLength = 0;//记录已下载文件大小  int rangeSwitch = 0;//0：从头开始的全文下载；1：从某字节开始的下载（bytes=27000-）；2：从某字节开始到某字节结束的下载（bytes=27000-39000）  long toLength = 0;//记录客户端需要下载的字节段的最后一个字节偏移量（比如bytes=27000-39000，则这个值是为39000）  long contentLength = 0;//客户端请求的字节总量  String rangeBytes = "";//记录客户端传来的形如“bytes=27000-”或者“bytes=27000-39000”的内容  RandomAccessFile raf = null;//负责读取数据  OutputStream os = null;//写出数据  OutputStream out = null;//缓冲  byte b[] = new byte[1024];//暂存容器    if (request.getHeader("Range") != null) {// 客户端请求的下载的文件块的开始字节  response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT);  log.info("request.getHeader(\"Range\")=" + request.getHeader("Range"));  rangeBytes = request.getHeader("Range").replaceAll("bytes=", "");  if (rangeBytes.indexOf('-') == rangeBytes.length() - 1) {//bytes=969998336-  rangeSwitch = 1;  rangeBytes = rangeBytes.substring(0, rangeBytes.indexOf('-'));  pastLength = Long.parseLong(rangeBytes.trim());  contentLength = fileLength - pastLength + 1;//客户端请求的是 969998336 之后的字节  } else {//bytes=1275856879-1275877358  rangeSwitch = 2;  String temp0 = rangeBytes.substring(0,rangeBytes.indexOf('-'));  String temp2 = rangeBytes.substring(rangeBytes.indexOf('-') + 1, rangeBytes.length());  pastLength = Long.parseLong(temp0.trim());//bytes=1275856879-1275877358，从第 1275856879 个字节开始下载  toLength = Long.parseLong(temp2);//bytes=1275856879-1275877358，到第 1275877358 个字节结束  contentLength = toLength - pastLength + 1;//客户端请求的是 1275856879-1275877358 之间的字节  }  } else {//从开始进行下载  contentLength = fileLength;//客户端要求全文下载  }    /**  * 如果设设置了Content-Length，则客户端会自动进行多线程下载。如果不希望支持多线程，则不要设置这个参数。  * 响应的格式是:  * Content-Length: [文件的总大小] - [客户端请求的下载的文件块的开始字节]  * ServletActionContext.getResponse().setHeader("Content-Length",  * new Long(file.length() - p).toString());  */  response.reset();//告诉客户端允许断点续传多线程连接下载,响应的格式是:Accept-Ranges: bytes  response.setHeader("Accept-Ranges", "bytes");//如果是第一次下,还没有断点续传,状态是默认的 200,无需显式设置;响应的格式是:HTTP/1.1 200 OK  if (pastLength != 0) {  //不是从最开始下载,  //响应的格式是:  //Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]  log.info("----------------------------不是从开始进行下载！服务器即将开始断点续传...");  switch (rangeSwitch) {  case 1 : {//针对 bytes=27000- 的请求  String contentRange = new StringBuffer("bytes ").append(new Long(pastLength).toString()).append("-").append(new Long(fileLength - 1).toString()).append("/").append(new Long(fileLength).toString()).toString();  response.setHeader("Content-Range", contentRange);  break;  }  case 2 : {//针对 bytes=27000-39000 的请求  String contentRange = rangeBytes + "/" + new Long(fileLength).toString();  response.setHeader("Content-Range", contentRange);  break;  }  default : {  break;  }  }  } else {  //是从开始下载  log.info("----------------------------是从开始进行下载！");  }    try {  response.addHeader("Content-Disposition", "attachment; filename=\"" + downloadFile.getName() + "\"");  response.setContentType( CommonUtil.setContentType(downloadFile.getName()));// set the MIME type.  response.addHeader("Content-Length", String.valueOf(contentLength));  os = response.getOutputStream();  out = new BufferedOutputStream(os);  raf = new RandomAccessFile(downloadFile, "r");  try {  switch (rangeSwitch) {  case 0 : {//普通下载，或者从头开始的下载  //同1  }  case 1 : {//针对 bytes=27000- 的请求  raf.seek(pastLength);//形如 bytes=969998336- 的客户端请求，跳过 969998336 个字节  int n = 0;  while ((n = raf.read(b, 0, 1024)) != -1) {  out.write(b, 0, n);  }  break;  }  case 2 : {//针对 bytes=27000-39000 的请求  raf.seek(pastLength - 1);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节  int n = 0;  long readLength = 0;//记录已读字节数  while (readLength <= contentLength - 1024) {//大部分字节在这里读取  n = raf.read(b, 0, 1024);  readLength += 1024;  out.write(b, 0, n);  }  if (readLength <= contentLength) {//余下的不足 1024 个字节在这里读取  n = raf.read(b, 0, (int)(contentLength - readLength));  out.write(b, 0, n);  }  //  // raf.seek(pastLength);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节  // while (raf.getFilePointer() < toLength) {  // out.write(raf.read());  // }  break;  }  default : {  break;  }  }  out.flush();  } catch(IOException ie) {  /**  * 在写数据的时候，  * 对于 ClientAbortException 之类的异常，  * 是因为客户端取消了下载，而服务器端继续向浏览器写入数据时，  * 抛出这个异常，这个是正常的。  * 尤其是对于迅雷这种吸血的客户端软件，  * 明明已经有一个线程在读取 bytes=1275856879-1275877358，  * 如果短时间内没有读取完毕，迅雷会再启第二个、第三个。。。线程来读取相同的字节段，  * 直到有一个线程读取完毕，迅雷会 KILL 掉其他正在下载同一字节段的线程，  * 强行中止字节读出，造成服务器抛 ClientAbortException。  * 所以，我们忽略这种异常  */  //ignore  }  } catch (Exception e) {  log.error(e.getMessage(), e);  } finally {  if (out != null) {  try {  out.close();  } catch (IOException e) {  log.error(e.getMessage(), e);  }  }  if (raf != null) {  try {  raf.close();  } catch (IOException e) {  log.error(e.getMessage(), e);  }  }  }  }  }      ArcSyncHttpDownloadServlet 的 web.xml 配置清单：  [html] view plaincopyprint?  <!-- HTTP 断点续传 demo:127.0.0.1/cds/http -->  <servlet>  <servlet-name>httpServlet</servlet-name>  <servlet-class>com.defonds.cds.common.ArcSyncHttpDownloadServlet</servlet-class>  </servlet>  <servlet-mapping>  <servlet-name>httpServlet</servlet-name>  <url-pattern>/http</url-pattern>  </servlet-mapping>      ArcSyncHttpDownloadServlet 调用到的工具类 com.defonds.cds.common.util.CommonUtil 源代码：  [java] view plaincopyprint?  package com.defonds.cds.common.util;    public class CommonUtil {    public static String setContentType(String returnFileName){  String contentType = "application/octet-stream";  if (returnFileName.lastIndexOf(".") < 0)  return contentType;  returnFileName = returnFileName.toLowerCase();  returnFileName = returnFileName.substring(returnFileName.lastIndexOf(".")+1);    if (returnFileName.equals("html") || returnFileName.equals("htm") || returnFileName.equals("shtml")){  contentType = "text/html";  } else if (returnFileName.equals("css")){  contentType = "text/css";  } else if (returnFileName.equals("xml")){  contentType = "text/xml";  } else if (returnFileName.equals("gif")){  contentType = "image/gif";  } else if (returnFileName.equals("jpeg") || returnFileName.equals("jpg")){  contentType = "image/jpeg";  } else if (returnFileName.equals("js")){  contentType = "application/x-javascript";  } else if (returnFileName.equals("atom")){  contentType = "application/atom+xml";  } else if (returnFileName.equals("rss")){  contentType = "application/rss+xml";  } else if (returnFileName.equals("mml")){  contentType = "text/mathml";  } else if (returnFileName.equals("txt")){  contentType = "text/plain";  } else if (returnFileName.equals("jad")){  contentType = "text/vnd.sun.j2me.app-descriptor";  } else if (returnFileName.equals("wml")){  contentType = "text/vnd.wap.wml";  } else if (returnFileName.equals("htc")){  contentType = "text/x-component";  } else if (returnFileName.equals("png")){  contentType = "image/png";  } else if (returnFileName.equals("tif") || returnFileName.equals("tiff")){  contentType = "image/tiff";  } else if (returnFileName.equals("wbmp")){  contentType = "image/vnd.wap.wbmp";  } else if (returnFileName.equals("ico")){  contentType = "image/x-icon";  } else if (returnFileName.equals("jng")){  contentType = "image/x-jng";  } else if (returnFileName.equals("bmp")){  contentType = "image/x-ms-bmp";  } else if (returnFileName.equals("svg")){  contentType = "image/svg+xml";  } else if (returnFileName.equals("jar") || returnFileName.equals("var") || returnFileName.equals("ear")){  contentType = "application/java-archive";  } else if (returnFileName.equals("doc")){  contentType = "application/msword";  } else if (returnFileName.equals("pdf")){  contentType = "application/pdf";  } else if (returnFileName.equals("rtf")){  contentType = "application/rtf";  } else if (returnFileName.equals("xls")){  contentType = "application/vnd.ms-excel";  } else if (returnFileName.equals("ppt")){  contentType = "application/vnd.ms-powerpoint";  } else if (returnFileName.equals("7z")){  contentType = "application/x-7z-compressed";  } else if (returnFileName.equals("rar")){  contentType = "application/x-rar-compressed";  } else if (returnFileName.equals("swf")){  contentType = "application/x-shockwave-flash";  } else if (returnFileName.equals("rpm")){  contentType = "application/x-redhat-package-manager";  } else if (returnFileName.equals("der") || returnFileName.equals("pem") || returnFileName.equals("crt")){  contentType = "application/x-x509-ca-cert";  } else if (returnFileName.equals("xhtml")){  contentType = "application/xhtml+xml";  } else if (returnFileName.equals("zip")){  contentType = "application/zip";  } else if (returnFileName.equals("mid") || returnFileName.equals("midi") || returnFileName.equals("kar")){  contentType = "audio/midi";  } else if (returnFileName.equals("mp3")){  contentType = "audio/mpeg";  } else if (returnFileName.equals("ogg")){  contentType = "audio/ogg";  } else if (returnFileName.equals("m4a")){  contentType = "audio/x-m4a";  } else if (returnFileName.equals("ra")){  contentType = "audio/x-realaudio";  } else if (returnFileName.equals("3gpp") || returnFileName.equals("3gp")){  contentType = "video/3gpp";  } else if (returnFileName.equals("mp4") ){  contentType = "video/mp4";  } else if (returnFileName.equals("mpeg") || returnFileName.equals("mpg") ){  contentType = "video/mpeg";  } else if (returnFileName.equals("mov")){  contentType = "video/quicktime";  } else if (returnFileName.equals("flv")){  contentType = "video/x-flv";  } else if (returnFileName.equals("m4v")){  contentType = "video/x-m4v";  } else if (returnFileName.equals("mng")){  contentType = "video/x-mng";  } else if (returnFileName.equals("asx") || returnFileName.equals("asf")){  contentType = "video/x-ms-asf";  } else if (returnFileName.equals("wmv")){  contentType = "video/x-ms-wmv";  } else if (returnFileName.equals("avi")){  contentType = "video/x-msvideo";  }    return contentType;  }      }