通过url 下载文件详解编程语言

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:[email protected]", "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:[email protected]","2x.png",request);