DownloadURLFile網絡文件下載

import java.io.BufferedOutputStream; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import javax.servlet.http.HttpServletResponse; import com.hurong.credit.util.RsaHelper; public class DownloadURLFile {          private static final DownloadURLFile downloadURLFile = new DownloadURLFile();             public static DownloadURLFile getInstance()          {                    return downloadURLFile;          }                    /**               * 執行下載               * @param rfPosit 遠程文件開始下載位置               */               public static void start(long rfPosit,URL remoteFile,File storeFile){                   HttpURLConnection httpConn = null;                   InputStream httpIn = null;                   try{                       System.out.println("打開HttpURLConnection.");                                httpConn = (HttpURLConnection)remoteFile.openConnection();                       httpConn.setRequestProperty("User-Agent","NetFox");                        httpConn.setRequestProperty("RANGE","bytes="+rfPosit+"-");                          System.out.println("獲得HttpInputStream.");                       httpIn = httpConn.getInputStream();                       writeFile(httpIn,storeFile);                       System.out.println("關閉HttpURLConnection.");                       httpConn.disconnect();                   }catch(Exception ex){                       ex.printStackTrace();                   }               }                              /**               * 從HttpInputStream中讀數據並寫到本地文件中               * @param in HttpInputStream               */               private static void writeFile(InputStream in,File storeFile){                   RandomAccessFile fileOut = null;                   int buffer_len = 512;                   byte[] buffer = new byte[buffer_len];                   int readLen = 0;                   try{                       System.out.println("寫本地文件.");                       fileOut = new RandomAccessFile(storeFile, "rw");                       fileOut.seek(fileOut.length());                       while(-1 != (readLen = in.read(buffer, 0, buffer_len))){                           fileOut.write(buffer, 0, readLen);                       }                           fileOut.close();                   }catch(Exception ex){                       ex.printStackTrace();                   }               }                            /**               * 大文件下載               * @param path               * @param response               */              public static void downLoad(String path, HttpServletResponse response){                       final int BUFFER_SIZE = 0x3000;// 緩衝區大小爲3M                       boolean isInline = false; // 是否容許直接在瀏覽器內打開                             OutputStream toClient = null;                             File f=new File(path);                                              /**                   *                   * map(FileChannel.MapMode mode,long position, long size)                   *                   * mode - 根據是按只讀、讀取/寫入或專用（寫入時拷貝）來映射文件，分別爲 FileChannel.MapMode 類中所定義的                   * READ_ONLY、READ_WRITE 或 PRIVATE 之一                   *                   * position - 文件中的位置，映射區域今後位置開始；必須爲非負數                   *                   * size - 要映射的區域大小；必須爲非負數且不大於 Integer.MAX_VALUE                   *                   * 因此若想讀取文件後半部份內容，如例子所寫；若想讀取文本後1/8內容，須要這樣寫map(FileChannel.MapMode.READ_ONLY,                   * f.length()*7/8,f.length()/8)                   *                   * 想讀取文件全部內容，須要這樣寫map(FileChannel.MapMode.READ_ONLY, 0,f.length())                   *                   */                             MappedByteBuffer inputBuffer=null;                  long start = 0;                             try {                                           String filename = new String(f.getName().getBytes(), "ISO8859-1");                                      String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();                                      response.reset();                                                                            String inlineType = isInline ? "inline" : "attachment"; // 是否內聯附件                                      response.setHeader("content-disposition", "attachment;filename=\""+ filename + "\"");                                      //response.setContentType("application/pdf");                                                                          inputBuffer = new RandomAccessFile(f, "r").getChannel().map(FileChannel.MapMode.READ_ONLY, 0,f.length());                  　　　　　　　byte[] dst = new byte[BUFFER_SIZE];// 每次讀出3M的內容                   start = System.currentTimeMillis();                  // if(inputBuffer.capacity()>BUFFER_SIZE){                  for (int offset = 0; offset < inputBuffer.capacity(); offset += BUFFER_SIZE) {                           if (inputBuffer.capacity() - offset >= BUFFER_SIZE) {                          for (int i = 0; i < BUFFER_SIZE; i++)                              dst[i] = inputBuffer.get(offset + i);                                } else {                                     for (int i = 0; i < inputBuffer.capacity() - offset; i++)                                         dst[i] = inputBuffer.get(offset + i);                      }                      toClient = new BufferedOutputStream(response.getOutputStream());                                      response.setContentType("application/octet-stream;charset=gbk");                                      toClient.write(dst);                  }                   /*}else{                            //dst[0]=inputBuffer;                            toClient = new BufferedOutputStream(response.getOutputStream());                                                response.setContentType("application/octet-stream;charset=gbk");                                                toClient.write(inputBuffer.get(0));                   }*/                             } catch (FileNotFoundException e) {                                      e.printStackTrace();                             } catch (IOException e) {                                      e.printStackTrace();                             } finally {                                      try {                                                     if (null != toClient) {                                                         toClient.close();                                                         toClient.flush();                                                }                                      } catch (Exception e) {                                                e.printStackTrace();                                      }                             }                  long end = System.currentTimeMillis();                  System.out.println("讀取文件文件內容花費：" + (end - start) + "毫秒");              } }