java断点续传服务端代码

此类核心续传servlet
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import java.io.BufferedOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.util.concurrent.ConcurrentSkipListMap;
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 org.springframework.util.Assert;

//HTTP 断点续传 demo（客户端测试工具：快车、迅雷）
public class MyHttpDownloadServlet 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) {
           String name = request. getParameter("filename");

            try {
                 log.info( "请求下载的连接地址为：" + request.getRequestURL() + "?" + request.getQueryString());
                Assert. hasText(name);
           } catch (IllegalArgumentException e) {
                 log.error( "请求下载的文件名参数为空！" );
                 return;
           }
           String path = "D:/Install/" + name;
            log.info( "文件拼装路径：" + path);
           File downloadFile = new File(path);
            if (downloadFile.exists()) {
                 if (downloadFile.isFile()) {
                      if (downloadFile.length() > 0) {
                     } else {
                            log.info( "请求下载的文件是一个空文件" );
                            return;
                     }
                      if (!downloadFile.canRead()) {
                            log.info( "请求下载的文件不是一个可读的文件" );
                            return;
                     } else {
                     }
                } else {
                      log.info( "请求下载的文件是一个文件夹" );
                      return;
                }
           } else {
                 log.info( "请求下载的文件不存在！" );
                 return;
           }

            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; // 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; // 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); // 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);
                           }
                            break;
                     }
                      default: {
                            break;
                     }
                     }
                     out.flush();
                      log.info( "------------------------------下载结束" );
                } 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
                      log.info( "#提醒# 向客户端传输时出现IO异常，但此异常是允许的的，有可能客户端取消了下载，导致此异常，不用关心！" );
                }
           } 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);
                     }
                }
           }
     }
}

此类是根据扩展名返回ContentType类型
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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("apk")) {
                contentType = "application/vnd.android.package-archive" ;
           } else if ( returnFileName.equals("sis")) {
                contentType = "application/vnd.symbian.install";
           } else if ( returnFileName.equals("sisx")) {
                contentType = "application/vnd.symbian.install";
           } else if ( returnFileName.equals("exe")) {
                contentType = "application/x-msdownload";
           } else if ( returnFileName.equals("msi")) {
                contentType = "application/x-msdownload";
           } 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;
     }

}

web.xml中servlet标签
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               <servlet>
             <description></ description>
             <display-name> ArcSyncHttpDownloadServlet</display-name >
             <servlet-name> ArcSyncHttpDownloadServlet</servlet-name >
             <servlet-class> com.MyHttpDownloadServlet</servlet-class >
       </servlet>
       <servlet-mapping>
             <servlet-name> ArcSyncHttpDownloadServlet</servlet-name >
             <url-pattern> /http</url-pattern >
       </servlet-mapping>

此类为测试类
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import java.io.BufferedInputStream;
import java.io.File;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLDecoder;

public class TestDownload {

    /**
     * @param args
     */
    public static void main(String[] args) {
        HttpURLConnection httpURLConnection = null;
        URL url = null;
        BufferedInputStream bis = null;
        byte[] buf = new byte[10240];
        int size = 0;
        String fileName = "a.exe";
        String filePath = "C:/Documents and Settings/Administrator/桌面";
        StringremoteUrl= "http://10.10.129.99:8080/project/http?filename=a.exe" ;
        
        // 检查本地文件
        RandomAccessFile rndFile = null;
        File file = new File(filePath + "\\" + fileName);
//        long remoteFileSize = getRemoteFileSzie(remoteUrl);
//        long nPos = 0;
        long localFileSzie =0;
        if (file.exists()) {                      
           localFileSzie = file.length();
        } else {
            // 建立文件
            try {
                file.createNewFile();
            } catch (Exception e) {
                e.printStackTrace();
            }          
        }
      
        // 下载文件
        try {
            url = new URL(remoteUrl);      
            httpURLConnection = (HttpURLConnection)url.openConnection();
            // 设置User-Agent
            httpURLConnection.setRequestProperty( "User-Agent", "Net");
            // 设置续传开始
            System. out.println( "本地文件大小：" +localFileSzie);
            httpURLConnection.setRequestProperty( "Range", "bytes=" + localFileSzie  + "-" );
            // 获取输入流
            bis = new BufferedInputStream(httpURLConnection.getInputStream());  
           
            long remoteFileSize = httpURLConnection.getContentLength();
            System. out.println( "返回结果码：" +httpURLConnection.getHeaderField("result"));
            //System.out.println("文件名："+httpURLConnection.getHeaderField("Content-Disposition"));
                 if (localFileSzie < remoteFileSize) {
                      if (localFileSzie==0) {
                           System. out.println( "文件不存在，开始下载..." );
                     } else{
                           System. out.println( "文件续传..." );
                     }
                } else {
                     System. out.println( "文件存在，重新下载..." );
                     file.delete();
                      try {
                           file.createNewFile();
                     } catch (Exception e) {
                           e.printStackTrace();
                     }
                }
           
            rndFile = new RandomAccessFile(filePath + "\\" + fileName, "rw");
       
            rndFile.seek(localFileSzie);
            int i = 0;
            while ((size = bis.read(buf)) != -1) {
                //if (i > 500) break;              
                rndFile.write(buf, 0, size);
                i++;
            }
            System. out.println( "i=" + i);
            httpURLConnection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static long getRemoteFileSzie(String url) {
        long size = 0;
        try {
            HttpURLConnection httpUrl = (HttpURLConnection)( new URL(url)).openConnection();
            size = httpUrl.getContentLength();
            httpUrl.disconnect();          
        } catch (Exception e) {
            e.printStackTrace();
        }
        return size;
    }
}