java實現斷點續傳

用java的URL實現了一個簡單的斷點續傳的列子，不為別的，假如你對斷點續傳不了解一看就明白了呵呵，算不上高深啊

package test;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
/* @className:TestDown.java

@classDescription: 簡單的java斷點續傳
@author:jiangmianyue
@createTime:2011-11-29
*/
public class TestDown {
 public static void main(String[] args) {
 URL url = null;
 try {
     url = new URL("http://172.16.1.33/newfile/e358beb5367341929614332e1a390dfb.apk");
 } catch (MalformedURLException e) {
     e.printStackTrace();
 }
 URLConnection httpConnection = null;
 try {
     // 建立連接
     httpConnection = url.openConnection();
 } catch (IOException e) {
     e.printStackTrace();
 }
  // 設置ua
  httpConnection.setRequestProperty("User-Agent","NetFox"); 
 // 設置斷點續傳的開始位置 從100k開始
 httpConnection.setRequestProperty("RANGE","bytes=102400-");
 // 獲得輸入流 
 InputStream input = null;
 try {
     input = httpConnection.getInputStream();
 } catch (IOException e) {
     e.printStackTrace();
 } 
 // 可以從多少字節開始寫的文件類
 RandomAccessFile oSavedFile = null;
 try {
     oSavedFile = new RandomAccessFile("d://down.apk","rw");
 } catch (FileNotFoundException e) {
     e.printStackTrace();
 } 
 // 從第100K開始寫
 long nPos = 102400; 
 // 定位文件指針到 nPos 位置 
 try {
 // 文件指針移動到那個位置
     oSavedFile.seek(nPos);
 } catch (IOException e) {
     e.printStackTrace();
 } 
 byte[] b = new byte[1024]; 
 int nRead; 
 // 從輸入流中讀入字節流，然后寫到文件中 
 try {
     // int n =0;
     while((nRead=input.read(b,0,1024)) > 0) 
     { 
     oSavedFile.write(b,0,nRead); 
     /**
      * 第一次的時設置n的值到100的時候斷開
      * if(100 == n){
      *     break;
      * }
      */
     }
 } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
 } 

 }
 // 下面是一些請求頭信息可以根據需要添加
 private static void setHeader(URLConnection con) {
 con.setRequestProperty("User-Agent", "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.3) Gecko/2008092510 Ubuntu/8.04 (hardy) Firefox/3.0.3");
 con.setRequestProperty("Accept-Language", "en-us,en;q=0.7,zh-cn;q=0.3");
 con.setRequestProperty("Accept-Encoding", "aa");
 con.setRequestProperty("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");
 con.setRequestProperty("Keep-Alive", "300");
 con.setRequestProperty("Connection", "keep-alive");
 con.setRequestProperty("If-Modified-Since", "Fri, 02 Jan 2009 17:00:05 GMT");
 con.setRequestProperty("If-None-Match", "\"1261d8-4290-df64d224\"");
 con.setRequestProperty("Cache-Control", "max-age=0");
 con.setRequestProperty("Referer", "http://www.dianping.com");

 }
}</pre>轉自： 
http://xuehanxin.iteye.com/blog/1284272