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Java 服务器端支持断点续传的源代码【支持快车、迅雷】

来源：互联网 发布：免费的api数据接口 编辑：程序博客网 时间：2024/06/03 16:00
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?
  1. package com.defonds.cds.common; 
  2.  
  3. import java.io.BufferedOutputStream; 
  4. import java.io.File; 
  5. import java.io.IOException; 
  6. import java.io.OutputStream; 
  7. import java.io.RandomAccessFile; 
  8.  
  9. import javax.servlet.ServletException; 
  10. import javax.servlet.http.HttpServlet; 
  11. import javax.servlet.http.HttpServletRequest; 
  12. import javax.servlet.http.HttpServletResponse; 
  13.  
  14. import org.apache.commons.logging.Log; 
  15. import org.apache.commons.logging.LogFactory; 
  16.  
  17. import com.defonds.cds.common.util.CommonUtil; 
  18.  
  19. //HTTP 断点续传 demo（客户端测试工具：快车、迅雷） 
  20. public class ArcSyncHttpDownloadServletextends HttpServlet { 
  21.     private staticfinal long serialVersionUID = 1L; 
  22.     final static Log log = LogFactory.getLog(ArcSyncHttpDownloadServlet.class); 
  23.      
  24.     @Override 
  25.     protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
  26.             throws ServletException, IOException { 
  27.         this.doPost(req, resp); 
  28.     } 
  29.      
  30.     @Override 
  31.     protected void doPost(HttpServletRequest request, HttpServletResponse response) { 
  32.         File downloadFile = new File("D:/defonds/book/pattern/SteveJobsZH.pdf");//要下载的文件 
  33.         long fileLength = downloadFile.length();//记录文件大小 
  34.         long pastLength = 0;//记录已下载文件大小 
  35.         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） 
  36.         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） 
  37.         long contentLength =0;//客户端请求的字节总量 
  38.         String rangeBytes = "";//记录客户端传来的形如“bytes=27000-”或者“bytes=27000-39000”的内容 
  39.         RandomAccessFile raf = null;//负责读取数据 
  40.         OutputStream os = null;//写出数据 
  41.         OutputStream out = null;//缓冲 
  42.         byte b[] = newbyte[1024];//暂存容器 
  43.          
  44.         if (request.getHeader("Range") !=null) {// 客户端请求的下载的文件块的开始字节 
  45.             response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT); 
  46.             log.info("request.getHeader(\"Range\")=" + request.getHeader("Range")); 
  47.             rangeBytes = request.getHeader("Range").replaceAll("bytes=",""); 
  48.             if (rangeBytes.indexOf('-') == rangeBytes.length() -1) {//bytes=969998336- 
  49.                 rangeSwitch = 1; 
  50.                 rangeBytes = rangeBytes.substring(0, rangeBytes.indexOf('-')); 
  51.                 pastLength = Long.parseLong(rangeBytes.trim()); 
  52.                 contentLength = fileLength - pastLength + 1;//客户端请求的是 969998336 之后的字节 
  53.             } else {//bytes=1275856879-1275877358 
  54.                 rangeSwitch = 2; 
  55.                 String temp0 = rangeBytes.substring(0,rangeBytes.indexOf('-')); 
  56.                 String temp2 = rangeBytes.substring(rangeBytes.indexOf('-') +1, rangeBytes.length()); 
  57.                 pastLength = Long.parseLong(temp0.trim());//bytes=1275856879-1275877358，从第 1275856879 个字节开始下载 
  58.                 toLength = Long.parseLong(temp2);//bytes=1275856879-1275877358，到第 1275877358 个字节结束 
  59.                 contentLength = toLength - pastLength + 1;//客户端请求的是 1275856879-1275877358  之间的字节 
  60.             } 
  61.         } else {//从开始进行下载 
  62.             contentLength = fileLength;//客户端要求全文下载 
  63.         } 
  64.          
  65.         /**
  66.          * 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。
  67.          * 响应的格式是:
  68.          * 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]
  69.          * ServletActionContext.getResponse().setHeader("Content-Length",
  70.          * new Long(file.length() - p).toString());
  71.          */ 
  72.         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 
  73.         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 
  74.         if (pastLength != 0) { 
  75.             //不是从最开始下载, 
  76.             //响应的格式是: 
  77.             //Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小] 
  78.             log.info("----------------------------不是从开始进行下载！服务器即将开始断点续传..."); 
  79.             switch (rangeSwitch) { 
  80.                 case 1 : {//针对 bytes=27000- 的请求 
  81.                     String contentRange = new StringBuffer("bytes ").append(new Long(pastLength).toString()).append("-").append(new Long(fileLength - 1).toString()).append("/").append(new Long(fileLength).toString()).toString(); 
  82.                     response.setHeader("Content-Range", contentRange); 
  83.                     break; 
  84.                 } 
  85.                 case 2 : {//针对 bytes=27000-39000 的请求 
  86.                     String contentRange = rangeBytes + "/" + new Long(fileLength).toString(); 
  87.                     response.setHeader("Content-Range", contentRange); 
  88.                     break; 
  89.                 } 
  90.                 default : { 
  91.                     break; 
  92.                 } 
  93.             } 
  94.         } else { 
  95.             //是从开始下载 
  96.             log.info("----------------------------是从开始进行下载！"); 
  97.         } 
  98.          
  99.         try { 
  100.             response.addHeader("Content-Disposition","attachment; filename=\"" + downloadFile.getName() +"\""); 
  101.             response.setContentType( CommonUtil.setContentType(downloadFile.getName()));// set the MIME type. 
  102.             response.addHeader("Content-Length", String.valueOf(contentLength)); 
  103.             os = response.getOutputStream(); 
  104.             out = new BufferedOutputStream(os); 
  105.             raf = new RandomAccessFile(downloadFile,"r"); 
  106.             try { 
  107.                 switch (rangeSwitch) { 
  108.                     case 0 : {//普通下载，或者从头开始的下载 
  109.                         //同1 
  110.                     } 
  111.                     case1 : {//针对 bytes=27000- 的请求 
  112.                         raf.seek(pastLength);//形如 bytes=969998336- 的客户端请求，跳过 969998336  个字节 
  113.                         int n =0; 
  114.                         while ((n = raf.read(b,0, 1024)) != -1) { 
  115.                             out.write(b, 0, n); 
  116.                         } 
  117.                         break; 
  118.                     } 
  119.                     case2 : {//针对 bytes=27000-39000 的请求 
  120.                         raf.seek(pastLength - 1);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节 
  121.                         int n =0; 
  122.                         long readLength =0;//记录已读字节数 
  123.                         while (readLength <= contentLength -1024) {//大部分字节在这里读取 
  124.                             n = raf.read(b, 0,1024); 
  125.                             readLength += 1024; 
  126.                             out.write(b, 0, n); 
  127.                         } 
  128.                         if (readLength <= contentLength) {//余下的不足 1024 个字节在这里读取 
  129.                             n = raf.read(b, 0, (int)(contentLength - readLength)); 
  130.                             out.write(b, 0, n); 
  131.                         } 
  132. //                       
  133. //                      raf.seek(pastLength);//形如 bytes=1275856879-1275877358 的客户端请求，找到第 1275856879 个字节 
  134. //                      while (raf.getFilePointer() < toLength) { 
  135. //                          out.write(raf.read()); 
  136. //                      } 
  137.                         break; 
  138.                     } 
  139.                     default : { 
  140.                         break; 
  141.                     } 
  142.                 } 
  143.                 out.flush(); 
  144.             } catch(IOException ie) { 
  145.                 /**
  146.                  * 在写数据的时候，
  147.                  * 对于 ClientAbortException 之类的异常，
  148.                  * 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，
  149.                  * 抛出这个异常，这个是正常的。
  150.                  * 尤其是对于迅雷这种吸血的客户端软件，
  151.                  * 明明已经有一个线程在读取 bytes=1275856879-1275877358，
  152.                  * 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，
  153.                  * 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，
  154.                  * 强行中止字节读出，造成服务器抛 ClientAbortException。
  155.                  * 所以，我们忽略这种异常
  156.                  */ 
  157.                 //ignore 
  158.             } 
  159.         } catch (Exception e) { 
  160.             log.error(e.getMessage(), e); 
  161.         } finally { 
  162.             if (out != null) { 
  163.                 try { 
  164.                     out.close(); 
  165.                 } catch (IOException e) { 
  166.                     log.error(e.getMessage(), e); 
  167.                 } 
  168.             } 
  169.             if (raf != null) { 
  170.                 try { 
  171.                     raf.close(); 
  172.                 } catch (IOException e) { 
  173.                     log.error(e.getMessage(), e); 
  174.                 } 
  175.             } 
  176.         } 
  177.     } 
  178. } 


        ArcSyncHttpDownloadServlet 的 web.xml 配置清单：

[html] view plaincopyprint?
  1.     <!-- HTTP 断点续传 demo:127.0.0.1/cds/http --> 
  2. <servlet> 
  3.     <servlet-name>httpServlet</servlet-name> 
  4.     <servlet-class>com.defonds.cds.common.ArcSyncHttpDownloadServlet</servlet-class> 
  5. </servlet>     
  6. <servlet-mapping> 
  7.     <servlet-name>httpServlet</servlet-name> 
  8.     <url-pattern>/http</url-pattern> 
  9. </servlet-mapping>     


        ArcSyncHttpDownloadServlet 调用到的工具类 com.defonds.cds.common.util.CommonUtil 源代码：

[java] view plaincopyprint?
  1. package com.defonds.cds.common.util; 
  2.  
  3. public class CommonUtil { 
  4.  
  5.     public static String setContentType(String returnFileName){ 
  6.         String contentType = "application/octet-stream"; 
  7.         if (returnFileName.lastIndexOf(".") <0) 
  8.             return contentType; 
  9.         returnFileName = returnFileName.toLowerCase(); 
  10.         returnFileName = returnFileName.substring(returnFileName.lastIndexOf(".")+1); 
  11.          
  12.         if (returnFileName.equals("html") || returnFileName.equals("htm") || returnFileName.equals("shtml")){ 
  13.             contentType = "text/html"; 
  14.         } else if (returnFileName.equals("css")){ 
  15.             contentType = "text/css"; 
  16.         } else if (returnFileName.equals("xml")){ 
  17.             contentType = "text/xml"; 
  18.         } else if (returnFileName.equals("gif")){ 
  19.             contentType = "image/gif"; 
  20.         } else if (returnFileName.equals("jpeg") || returnFileName.equals("jpg")){ 
  21.             contentType = "image/jpeg"; 
  22.         } else if (returnFileName.equals("js")){ 
  23.             contentType = "application/x-javascript"; 
  24.         } else if (returnFileName.equals("atom")){ 
  25.             contentType = "application/atom+xml"; 
  26.         } else if (returnFileName.equals("rss")){ 
  27.             contentType = "application/rss+xml"; 
  28.         } else if (returnFileName.equals("mml")){ 
  29.             contentType = "text/mathml";  
  30.         } else if (returnFileName.equals("txt")){ 
  31.             contentType = "text/plain"; 
  32.         } else if (returnFileName.equals("jad")){ 
  33.             contentType = "text/vnd.sun.j2me.app-descriptor"; 
  34.         } else if (returnFileName.equals("wml")){ 
  35.             contentType = "text/vnd.wap.wml"; 
  36.         } else if (returnFileName.equals("htc")){ 
  37.             contentType = "text/x-component"; 
  38.         } else if (returnFileName.equals("png")){ 
  39.             contentType = "image/png"; 
  40.         } else if (returnFileName.equals("tif") || returnFileName.equals("tiff")){ 
  41.             contentType = "image/tiff"; 
  42.         } else if (returnFileName.equals("wbmp")){ 
  43.             contentType = "image/vnd.wap.wbmp"; 
  44.         } else if (returnFileName.equals("ico")){ 
  45.             contentType = "image/x-icon"; 
  46.         } else if (returnFileName.equals("jng")){ 
  47.             contentType = "image/x-jng"; 
  48.         } else if (returnFileName.equals("bmp")){ 
  49.             contentType = "image/x-ms-bmp"; 
  50.         } else if (returnFileName.equals("svg")){ 
  51.             contentType = "image/svg+xml"; 
  52.         } else if (returnFileName.equals("jar") || returnFileName.equals("var") || returnFileName.equals("ear")){ 
  53.             contentType = "application/java-archive"; 
  54.         } else if (returnFileName.equals("doc")){ 
  55.             contentType = "application/msword"; 
  56.         } else if (returnFileName.equals("pdf")){ 
  57.             contentType = "application/pdf"; 
  58.         } else if (returnFileName.equals("rtf")){ 
  59.             contentType = "application/rtf"; 
  60.         } else if (returnFileName.equals("xls")){ 
  61.             contentType = "application/vnd.ms-excel";  
  62.         } else if (returnFileName.equals("ppt")){ 
  63.             contentType = "application/vnd.ms-powerpoint"; 
  64.         } else if (returnFileName.equals("7z")){ 
  65.             contentType = "application/x-7z-compressed"; 
  66.         } else if (returnFileName.equals("rar")){ 
  67.             contentType = "application/x-rar-compressed"; 
  68.         } else if (returnFileName.equals("swf")){ 
  69.             contentType = "application/x-shockwave-flash"; 
  70.         } else if (returnFileName.equals("rpm")){ 
  71.             contentType = "application/x-redhat-package-manager"; 
  72.         } else if (returnFileName.equals("der") || returnFileName.equals("pem") || returnFileName.equals("crt")){ 
  73.             contentType = "application/x-x509-ca-cert"; 
  74.         } else if (returnFileName.equals("xhtml")){ 
  75.             contentType = "application/xhtml+xml"; 
  76.         } else if (returnFileName.equals("zip")){ 
  77.             contentType = "application/zip"; 
  78.         } else if (returnFileName.equals("mid") || returnFileName.equals("midi") || returnFileName.equals("kar")){ 
  79.             contentType = "audio/midi"; 
  80.         } else if (returnFileName.equals("mp3")){ 
  81.             contentType = "audio/mpeg"; 
  82.         } else if (returnFileName.equals("ogg")){ 
  83.             contentType = "audio/ogg"; 
  84.         } else if (returnFileName.equals("m4a")){ 
  85.             contentType = "audio/x-m4a"; 
  86.         } else if (returnFileName.equals("ra")){ 
  87.             contentType = "audio/x-realaudio"; 
  88.         } else if (returnFileName.equals("3gpp") || returnFileName.equals("3gp")){ 
  89.             contentType = "video/3gpp"; 
  90.         } else if (returnFileName.equals("mp4") ){ 
  91.             contentType = "video/mp4"; 
  92.         } else if (returnFileName.equals("mpeg") || returnFileName.equals("mpg") ){ 
  93.             contentType = "video/mpeg"; 
  94.         } else if (returnFileName.equals("mov")){ 
  95.             contentType = "video/quicktime"; 
  96.         } else if (returnFileName.equals("flv")){ 
  97.             contentType = "video/x-flv"; 
  98.         } else if (returnFileName.equals("m4v")){ 
  99.             contentType = "video/x-m4v"; 
  100.         } else if (returnFileName.equals("mng")){ 
  101.             contentType = "video/x-mng"; 
  102.         } else if (returnFileName.equals("asx") || returnFileName.equals("asf")){ 
  103.             contentType = "video/x-ms-asf"; 
  104.         } else if (returnFileName.equals("wmv")){ 
  105.             contentType = "video/x-ms-wmv"; 
  106.         } else if (returnFileName.equals("avi")){ 
  107.             contentType = "video/x-msvideo"; 
  108.         } 
  109.          
  110.         return contentType; 
  111.     } 
  112.      
  113.      
  114. } 


        本文示例代码在客户端使用快车(FlashGet)3、迅雷7 进行断点续传的环境下测试 OK。

        本文仅为用来技术交流的演示 Demo，技术水平及知识面所限，其中错误和不当之处在所难免，敬请谅解。欢迎联系作者进行批评指正，技术交流 MSN：defonds#hotmail.com(#=@)，也可以给我发邮件，email：defonds#163.com(#=@)。

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