java下载网络文件的几种方式

java下载网络文件包括：基本的字节流下载，apache的FileUtils工具包下载，NIO下载

package com.dsp.rpc.metricelf;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.net.HttpURLConnection;
import java.net.URL;


public class DownloadZipUtil {

    /**
     * FileUtils下载网络文件
     *
     * @param serverUrl   ：网络文件地址
     * @param savePath：本地保存路径
     * @param zipSavePath ：压缩文件保存路径
     * @return
     */
    public static String downloadFile(String serverUrl, String savePath, String zipSavePath) throws Exception {
        String result;
        File f = new File(savePath);
        if (!f.exists()) {
            if (!f.mkdirs()) {
                throw new Exception("makdirs: '" + savePath + "'fail");
            }
        }
        URL url = new URL(serverUrl);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(3 * 1000);
        //防止屏蔽程序抓取而放回403错误
        conn.setRequestProperty("User-Agent", "Mozilla/4.0(compatible;MSIE 5.0;Windows NT;DigExt)");
        Long totalSize = Long.parseLong(conn.getHeaderField("Content-Length"));
        if (totalSize > 0) {
            FileUtils.copyURLToFile(url, new File(zipSavePath));
            result = "success";
        } else {
            throw new Exception("can not find serverUrl :{}" + serverUrl);
        }
        return result;
    }

 /**
     * 字节流下载压缩文件
     * @param serverUrl :网络地址
     * @param savePath ：保持路径
     * @param zipSavePath ：压缩文件保持路径
     * @return ：下载结果
     * @throws Exception ：异常
     */
    public static String downloadZip(String serverUrl,String savePath,String zipSavePath) throws Exception{
        String result = "fail";
        File f = new File(savePath);
        if(!f.exists()){
            if (!f.mkdirs()) {
                throw new Exception("makdirs: '" + savePath + "'fail");
            }
        }
        //Sardine是WebDAV的工具包
        Sardine sardine = SardineFactory.begin("test","test");
        if(sardine.exists(serverUrl)){
            URL url = new URL(serverUrl);
            URLConnection conn = url.openConnection();
            int length = conn.getContentLength();
            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)");
            InputStream is = sardine.getInputStream(serverUrl);
            BufferedInputStream bis = new BufferedInputStream(is);
            FileOutputStream fos = new FileOutputStream(zipSavePath);
            BufferedOutputStream bos = new BufferedOutputStream(fos);
            int len;
            byte[] bytes = new byte[length/5];
            while ((len = bis.read(bytes)) != -1) {
                bos.write(bytes, 0, len);
            }
            //清除缓存
            bos.flush();
            //关闭流
            fos.close();
            is.close();
            bis.close();
            bos.close();
            result = "success";

        }else {
             throw new Exception("can not find file");
        }
        return result;
    }



}