从网上下载文件在java中

Question

我正在使用下面的Java代码从网上下载数据。有些情况下，它工作正常。但是，有时会出现错误。可能是什么原因？

有一个在URL没有什么区别，因为我从他们的网站上复制它还有： http://www.nseindia.com/content/equities/scripvol/datafiles/07-04-2010-TO-01-04-2011TCSALLN.csv

我的网址是： http://www.nseindia.com/content/equities/scripvol/datafiles/07-04-2010-TO-01-04-2011TCSALLN.csv

所以，我看不出有什么差别。

错误：未找到：请求的对象在此服务器上不存在。您所遵循的链接要么过时，不准确，要么服务器已被指示不让您拥有它。

import java.io.FileOutputStream; 
import java.io.IOException; 
import java.net.URL; 
import java.nio.channels.Channels; 
import java.nio.channels.ReadableByteChannel; 
import java.text.DateFormat; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Date; 

public class AutomatedDownloader 
{ 
    private static FileOutputStream fos; 

    public static void main(String args[]) throws IOException, ParseException 
    { 
     String combo = "TCS"; 
     String userDate = "02-04-2011"; 

     Date date1, date2, date3; 

     SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy"); 
     DateFormat df = new SimpleDateFormat("dd-MM-yyyy"); 
     Calendar cal = Calendar.getInstance();  

     date1 = formatter.parse(userDate); 

     cal.setTime(date1); 
     cal.add(Calendar.DATE, -1); 
     date2 = cal.getTime(); 
     String endDate = df.format(date2); 
     System.out.println(endDate); 

     cal.setTime(date1); 
     cal.add(Calendar.DATE, - 360); 
     date3 = cal.getTime(); 
     String startDate = df.format(date3); 
     System.out.println(startDate); 

     String url ="http://www.nseindia.com/content/equities/scripvol/datafiles/"+startDate+"-TO-"+endDate+combo+"ALLN.csv"; 
     String fileName = "C:\\Users\\Parin\\Documents\\ParinAndroid\\StockPredictor\\DownloadedData\\"+combo+".csv"; 

     URL website = new URL(url); 
     ReadableByteChannel rbc = Channels.newChannel(website.openStream()); 
     fos = new FileOutputStream(fileName); 
     fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE); 
     System.out.print("done"); 
    } 

异常：

Exception: Exception in thread "main" java.io.FileNotFoundException: http://www.nseindia.com/content/equities/scripvol/datafiles/07-12-2013-TO-01-12-2014TCSALLN.csv 
     at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1243) 
     at java.net.URL.openStream(URL.java:1009) 
     at Predictor.AutomatedDownloader.main(AutomatedDownloader.java:46) 

Answer 1

我使用Jsoup库文件。下载Jsoup jar文件并将其添加到您的类路径中。下面的代码：

进口：

import java.io.FileOutputStream; 
import org.jsoup.Connection.Response; 
import org.jsoup.Jsoup; 

代码：

//Open a URL Stream 
Response resultImageResponse = Jsoup 
       .connect("http://www.nseindia.com/content/equities/scripvol/datafiles/07-04-2010-TO-01-04-2011TCSALLN.csv") 
       .ignoreContentType(true) 
       .userAgent("Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:25.0) Gecko/20100101 Firefox/25.0") 
       .execute(); 

// output here 
FileOutputStream out = (new FileOutputStream(new java.io.File("" + "file.csv"))); 
out.write(resultImageResponse.bodyAsBytes());   
out.close(); 

Answer 2

public static void main(String args[]) { 
    String index = "cnx nifty junior"; 
    String from_date = "01-03-2015"; 
    String to_date = "20-03-2015"; 
    download(index, from_date, to_date); 
} 

public static void download(String index, String from_date, String to_date) { 
    String link = "http://www.nseindia.com/products/dynaContent/equities/indices/historicalindices.jsp?indexType=" + index.replaceAll(" ", "%20").toUpperCase() + "&fromDate=" + from_date + "&toDate=" + to_date; 
    try { 
     URL url = new URL(link); 
     URLConnection connection = url.openConnection(); 
     connection.setReadTimeout(5000); 
     BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream())); 
     StringBuilder html = new StringBuilder(); 
     String line = reader.readLine(); 
     while (line != null) { 
      html.append(line); 
      line = reader.readLine(); 
     } 
     reader.close(); 
     Document document = Jsoup.parse(html.toString()); 
     Elements elements = document.getElementsByTag("a"); 
     Iterator<Element> iterator = elements.iterator(); 
     String downloadLink = null; 
     if (iterator.hasNext()) { 
      Element element = iterator.next(); 
      downloadLink = "http://www.nseindia.com" + element.attr("href"); 
     } 
     if (downloadLink != null) { 
       Runtime rt = Runtime.getRuntime(); 
       rt.exec("rundll32 url.dll,FileProtocolHandler " + downloadLink); 
     } 
    } catch (Exception ex) { 
     ex.printStackTrace(System.err); 
    } 
} 

它下载成功。您需要添加jsoup.jar库。但它只会在Windows操作系统上工作。