文件下载的 HTTP 协议实现

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();
 }
}