錯誤處理URLConnection

Question

我有這種方法，從雅虎財務下載.csv文件並將它們保存在本地。它在一個循環中被訪問，所以它從列表中下載了許多文件。但是有時候符號輸入不正確，不再存在，或連接超時。如何修改此方法，以便連接超時被重試，並且不正確的符號（意味着URL不起作用）只是跳過而不結束程序？

public static void get_file(String symbol){ 

    OutputStream outStream = null; 
    URLConnection uCon = null; 
    InputStream is = null; 

    String finance_url = "http://ichart.finance.yahoo.com/table.csv?s="+symbol; 
    String destination = "C:/"+symbol+"_table.csv"; 

    try { 
     URL Url; 
     byte[] buf; 
     int ByteRead,ByteWritten=0; 
     Url= new URL(finance_url); 

     outStream = new BufferedOutputStream(new FileOutputStream(destination)); 

     uCon = Url.openConnection(); 
     is = uCon.getInputStream();   
     buf = new byte[size]; 

     while ((ByteRead = is.read(buf)) != -1) { 
      outStream.write(buf, 0, ByteRead); 
      ByteWritten += ByteRead; 
     } 

    }catch (Exception e) { 
     System.out.println("Error while downloading "+symbol); 
     e.printStackTrace(); 
    }finally { 
     try { 
      is.close(); 
      outStream.close(); 
     }catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 
} 

Answer 1

爲什麼在拋出異常時再次調用該方法。您可以縮小異常類型以指示何時應該啓動重試。

public static void get_file(String symbol){ 

    OutputStream outStream = null; 
    URLConnection uCon = null; 
    InputStream is = null; 

    String finance_url = "http://ichart.finance.yahoo.com/table.csv?s="+symbol; 
    String destination = "C:/"+symbol+"_table.csv"; 

    try { 
     URL Url; 
     byte[] buf; 
     int ByteRead,ByteWritten=0; 
     Url= new URL(finance_url); 

     outStream = new BufferedOutputStream(new FileOutputStream(destination)); 

     uCon = Url.openConnection(); 
     is = uCon.getInputStream();   
     buf = new byte[size]; 

     while ((ByteRead = is.read(buf)) != -1) { 
      outStream.write(buf, 0, ByteRead); 
      ByteWritten += ByteRead; 
     } 

    }catch (Exception e) { 
     getFile(symbol); 
    }finally { 
     try { 
      is.close(); 
      outStream.close(); 
     }catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 
}