DownloadURLFile网络文件下载

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;

         }

                   /**

              * 执行下载

              * @param rfPosit 远程文件开始下载位置

              */ 

             public static void start(long rfPosit,URL remoteFile,File storeFile){ 

                 HttpURLConnection httpConn = null; 

                 InputStream httpIn = null; 

                 try{ 

                     System.out.println("打开HttpURLConnection.");          

                     httpConn = (HttpURLConnection)remoteFile.openConnection(); 

                     httpConn.setRequestProperty("User-Agent","NetFox");  

                     httpConn.setRequestProperty("RANGE","bytes="+rfPosit+"-");    

                     System.out.println("得到HttpInputStream."); 

                     httpIn = httpConn.getInputStream(); 

                     writeFile(httpIn,storeFile); 

                     System.out.println("关闭HttpURLConnection."); 

                     httpConn.disconnect(); 

                 }catch(Exception ex){ 

                     ex.printStackTrace(); 

                 } 

             } 

              

             /**

              * 从HttpInputStream中读数据并写到本地文件中

              * @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("写本地文件."); 

                     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(); 

                 } 

             } 

            

             /**

              * 大文件下载

              * @param path

              * @param response

              */

             public static void downLoad(String path, HttpServletResponse response){

                      final int BUFFER_SIZE = 0x3000;// 缓冲区大小为3M

                      boolean isInline = false; // 是否允许直接在浏览器内打开

                            OutputStream toClient = null;

                            File f=new File(path);

                           

                 /**

                  *

                  * map(FileChannel.MapMode mode,long position, long size)

                  *

                  * mode - 根据是按只读、读取/写入或专用（写入时拷贝）来映射文件，分别为 FileChannel.MapMode 类中所定义的

                  * READ_ONLY、READ_WRITE 或 PRIVATE 之一

                  *

                  * position - 文件中的位置，映射区域从此位置开始；必须为非负数

                  *

                  * size - 要映射的区域大小；必须为非负数且不大于 Integer.MAX_VALUE

                  *

                  * 所以若想读取文件后半部分内容，如例子所写；若想读取文本后1/8内容，需要这样写map(FileChannel.MapMode.READ_ONLY,

                  * f.length()*7/8,f.length()/8)

                  *

                  * 想读取文件所有内容，需要这样写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"; // 是否内联附件

                                     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];// 每次读出3M的内容

                  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("读取文件文件内容花费：" + (end - start) + "毫秒");

             }

}