HTTP协议实现文件下载

package com.dcfs.teller.event;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;/** * 从网络获取图片到本地 */public class GetImage { /**  * 测试  * @param args  */ public static void main(String[] args) {  String url = "http://www.baidu.com/img/baidu_test.gif";  byte[] btImg = getImageByUrl(url);  if(null != btImg && btImg.length > 0){   System.out.println("读取到：" + btImg.length + " 字节");   String fileName = "百度.gif";   writeImageToDisk(btImg, fileName);  }else{   System.out.println("没有从该连接获得内容");  } } /**  * 将图片写入到磁盘  * @param img 图片数据流  * @param fileName 文件保存时的名称  */ public static void writeImageToDisk(byte[] img, String fileName){  try {   File file = new File("D:\\" + fileName);   FileOutputStream fops = new FileOutputStream(file);   fops.write(img);   fops.flush();   fops.close();   System.out.println("图片已经写入到D盘");  } catch (Exception e) {   e.printStackTrace();  } } /**  * 根据地址获得数据的字节流  * @param strUrl 网络连接地址  * @return  */ public static byte[] getImageByUrl(String strUrl){  try {   URL url = new URL(strUrl);   HttpURLConnection conn = (HttpURLConnection)url.openConnection();   conn.setRequestMethod("GET");   conn.setConnectTimeout(5 * 1000);   InputStream inStream = conn.getInputStream();//通过输入流获取图片数据   byte[] btImg = readInputStream(inStream);//得到图片的二进制数据   return btImg;  } catch (Exception e) {   e.printStackTrace();  }  return null; } /**  * 从输入流中获取数据  * @param inStream 输入流  * @return  * @throws Exception  */ public static byte[] readInputStream(InputStream inStream) throws Exception{  ByteArrayOutputStream outStream = new ByteArrayOutputStream();  byte[] buffer = new byte[1024];  int len = 0;  while( (len=inStream.read(buffer)) != -1 ){   outStream.write(buffer, 0, len);  }  inStream.close();  return outStream.toByteArray(); }}