通过url下载文件

package com.zcr.until;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.util.Properties;public class GetFilePlace {    /**     * 读取文件，获取保存的根目录     * @return  保存的根目录     */    public   String getFilePath(String fileProperties)    {        String dir = System.getProperty("user.dir");  //获得tomcat所在的工作路径                  //获取到存储了文件存储位置的filedir.properties 文件路径       // String realDir = dir + File.separator + "src" + File.separator +"META-INF" + File.separator + "config" + File.separator + "picture.properties";       String realDir = dir.substring(0, dir.length()-4) + File.separator +"webapps" + File.separator + "appDataGenerate" +File.separator + "WEB-INF"                + File.separator + "classes" + File.separator + "META-INF" + File.separator + "config" + File.separator + fileProperties;              /* String realDir = dir.substring(0, dir.length()-4) + File.separator +"webapps" + File.separator + "appDataGenerate"                       + File.separator + "classes" + File.separator + "META-INF" + File.separator + "config" + File.separator + fileProperties;    */        System.out.println("realDir = " + realDir);        return realDir;    }            /**     * 获取filePath路径【properities文件】中key对应的值，     * @param filePath properities文件路径【包含properities文件】     * @param key 要查找的key值     * @return key对应的value     */     public   String GetValueByKey(String filePath, String key)      {         Properties pps = new Properties();         try {              InputStream in = new BufferedInputStream (new FileInputStream(filePath));                pps.load(in);             String value = pps.getProperty(key);             in.close();             return value;                      }catch (IOException e) {             e.printStackTrace();             return null;         }     }        /**     * 查询properities文件中可以对应的存储地点     * @param key 查询主键     * @return    key对应的存储地址     */    public  String getFileDirFromProperties(String key,String fileProperties)    {        return GetValueByKey(getFilePath(fileProperties),key);    }        public static void main(String[] args)    {        System.out.println(new GetFilePlace().getFileDirFromProperties("brandLogo","picture.properties"));    }}

package com.zcr.until;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;import javax.servlet.http.HttpServletRequest;public class URLConnectionDownloader{    
    //单纯测试下载    public static void main(String[] args)    {        download("http://stocardapp.s3-external-3.amazonaws.com/ios/icons/1001tur@2x.png", "E://xiazai.jpg");    }        /**     * 将urlString的文件下载到     * @param filePathName        properties文件中的文件存储名     * @param fileProperties    查找的properties文件         * @param urlString            待下载的文件url     * @param fileName             生成的文件名称     */    public static void downloadToSelectedFolder(String filePathName,String fileProperties,String urlString,String fileName,HttpServletRequest request)    {        //获得picture.properties 文件中，key为android_banner_url的值        String pathSavePath = new GetFilePlace().getFileDirFromProperties("android_banner_url","picture.properties");                //获得服务器（tomcat）pathSavePath的相对位置        String path = request.getsession().getServletContext().getRealPath(pathSavePath);                //获得文件存储的绝对路径        String generateFileName = path + File.separator + fileName;                download(urlString,generateFileName);    }                /**       * 下载文件到本地       *       * @param urlString       *          被下载的文件地址       * @param filename       *          本地文件名       */    public static void download(String urlString, String filename)      {        // 构造URL        URL url;        try        {            url = new URL(urlString);             // 打开连接            URLConnection con = url.openConnection();            // 输入流            InputStream is = con.getInputStream();            // 1K的数据缓冲            byte[] bs = new byte[1024];            // 读取到的数据长度            int len;            // 输出的文件流s            OutputStream os = new FileOutputStream(filename);            // 开始读取            while ((len = is.read(bs)) != -1) {              os.write(bs, 0, len);            }            // 完毕，关闭所有链接            os.close();            is.close();        }        catch (MalformedURLException e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }        catch (IOException e)        {            // TODO Auto-generated catch block            e.printStackTrace();        }    }   }

URLConnectionDownloader.downloadToSelectedFolder("android_banner_url","picture.properties","http://stocardapp.s3-external-3.amazonaws.com/ios/icons/1001tur@2x.png","2x.png",request);