java 下载网络文件

1.FileUtils.copyURLToFile实现：

import java.io.File;
import java.net.URL;
import org.apache.commons.io.FileUtils;

public class DownLoadFile {

    /**
     * 网络文件下载保存
     * @param url 文件url
     * @param dir 存储目录
     * @param fileName 存储文件名
     */
    public static void downloadHttpUrl(String url, String dir, String fileName) {  
        try {  
            URL httpurl = new URL(url);  
            File dirfile = new File(dir);    
            if (!dirfile.exists()) {    
                dirfile.mkdirs();  
            }  
            FileUtils.copyURLToFile(httpurl, new File(dir+fileName));
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    } 
    
    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        downloadHttpUrl("http://gtms03.alicdn.com/tps/i3/TB1VF6uGFXXXXalaXXXmh5R_VXX-237-236.png", "D:/download/", "1.png");
    }
}

图示：

               

2.常规写法：

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownLoadFile {

    /** 
     * 从网络Url中下载文件 
     *  
     * @param urlstr 文件url
     * @param fileName 存储文件名
     * @param savePath 存储路径
     * @throws IOException 
     */  
    public static String downLoadFromUrl(String urlStr, String fileName, String savePath) {  
        try {  
      
            URL url = new URL(urlStr);  
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();  
            // 设置超时间为3秒  
            conn.setConnectTimeout(3 * 1000);  
            // 防止屏蔽程序抓取而返回403错误  
            conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");  
      
            // 得到输入流  
            InputStream inputStream = conn.getInputStream();  
            // 获取自己数组  
            byte[] getData = readInputStream(inputStream);  
      
            // 文件保存位置  
            File saveDir = new File(savePath);  
            if (!saveDir.exists()) {  
                saveDir.mkdir();  
            }  
            File file = new File(saveDir + File.separator + fileName);  
            FileOutputStream fos = new FileOutputStream(file);  
            fos.write(getData);  
            if (fos != null) {  
                fos.close();  
            }  
            if (inputStream != null) {  
                inputStream.close();  
            }  
            // System.out.println("info:"+url+" download success");  
            return saveDir + File.separator + fileName;  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        return "";  
      
    }  
      
    /** 
     * 从输入流中获取字节数组 
     *  
     * @param inputStream 
     * @return 
     * @throws IOException 
     */  
    public static byte[] readInputStream(InputStream inputStream) throws IOException {  
        byte[] buffer = new byte[1024];  
        int len = 0;  
        ByteArrayOutputStream bos = new ByteArrayOutputStream();  
        while ((len = inputStream.read(buffer)) != -1) {  
            bos.write(buffer, 0, len);  
        }  
        bos.close();  
        return bos.toByteArray();  
    }  
    
    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        downLoadFromUrl("http://gtms03.alicdn.com/tps/i3/TB1VF6uGFXXXXalaXXXmh5R_VXX-237-236.png", "2.png", "D:/download/");
    }
    
}

图示：