調用一個將csv文件讀入servlet的類方法

Question

我正在編寫一個代碼，用於以連續循環的方式將多個發件人的電子郵件發送給一個收件人。我要讀的發件人csv文件EMAILID的，我已經寫了代碼raeding如下：

public class ReadFile { 

    CsvReader senders; 

    public CsvReader read(){ 

     try { 
      senders = new CsvReader("C:/Users/D/Documents/Senderlist.csv"); 
      senders.readHeaders(); 

      while (senders.readRecord()) 
      { 
       String SenderID = senders.get("SenderID"); 
       String ReceiverID = senders.get("ReceiverID"); 

       // perform program logic here 
       System.out.println(SenderID + " : " + ReceiverID); 
      } 

      senders.close(); 

     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     ArrayList<String> al=new ArrayList<String>(); 
     al.add("senders"); 
     //traversing list through iterator 
     Iterator itr=al.iterator(); 

     while(itr.hasNext()){ 
      System.out.println(itr.next()); 
     } 
     return senders; 

    } 

} 

現在我該如何調用這個方法在我的servlet讀取和連續循環發送電子郵件，servlet的是如下：

public class MailController extends HttpServlet { 

    private static final long serialVersionUID = 1L; 
    private String ExchangeIP; 
    private String port; 

    public MailController() { 
     super(); 
     // TODO Auto-generated constructor stub 
    } 

    public void init() { 
     // reads SMTP server setting from web.xml file 
     ServletContext context = getServletContext(); 
     ExchangeIP = context.getInitParameter("ExchangeIP"); 
     port = context.getInitParameter("port"); 
    } 

    /** 
    * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) 
    */ 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     // TODO Auto-generated method stub 
     doPost(request, response); 
    } 

    /** 
    * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) 
    */ 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
     // read from field 
     List<File> uploadedFiles= saveUploadedFiles(request); 
     String sender=request.getParameter("sender");// reading from the form page 
     String recipient=request.getParameter("recipient"); 
     String subject=request.getParameter("subject"); 
     String content=request.getParameter("content"); 
     String resultMessage = ""; 

     try { 
      EmailUtility.sendEmail(ExchangeIP, port,user, recipient, subject, content, uploadedFiles); 
     resultMessage = "The e-mail has been sent successfully"; 
     } catch (Exception ex) { 
      ex.printStackTrace(); 
      resultMessage = "There were an error: " + ex.getMessage(); 
     } finally { 
      //deleteUploadFiles(uploadedFiles); 
      request.setAttribute("Message", resultMessage); 
    getServletContext().getRequestDispatcher("/Result.jsp").forward(request, response); 
     } 

} 

Answer 1

如果你唯一擔心的是讀取CSV文件，重複你在Servlet該文件中讀取那麼你爲什麼不只需調用servlet中read()方法的項目？並改變read()方法這樣

public List<String> getSenderEmails() { 
     CsvReader senders = new CsvReader("C:/Users/D/Documents/Senderlist.csv"); 
     senders.readHeaders(); 

     List<String> senderEmails = new ArrayList<>(); 

     while (senders.readRecord()) { 
      String senderID = senders.get("SenderID"); 
      String receiverID = senders.get("ReceiverID"); 

      // perform program logic here 
      System.out.println(senderID + " : " + receiverID); 
      senderEmails.add(senderID); 
     } 

     return senderEmails; 
} 

NB：

• 我不知道什麼是您的CsvReader在做什麼。但假設它是一種圖書館或實用程序。所以必要的需要Exception handeling。
• 但我建議的主要想法是，而不是返回CsvReader或類似的東西，只是返回您只是關心的電子郵件地址列表。

接下來的事情是，你可以從servlet呼叫getSenderEmails()和遍歷它來發送電子郵件

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    // read from field 
    List<File> uploadedFiles = saveUploadedFiles(request); 
    String sender = request.getParameter("sender");// reading from the form page 
    String recipient = request.getParameter("recipient"); 
    String subject = request.getParameter("subject"); 
    String content = request.getParameter("content"); 
    String resultMessage = "";  

    try { 
     List<String> senderEmails = ReadFile.getSenderEmails(); 
     for (String user : senderEmails) { 
      EmailUtility.sendEmail(ExchangeIP, port, user, recipient, subject, content, uploadedFiles); 
     } 
     resultMessage = "The e-mail has been sent successfully"; 
    } catch (Exception ex) { 
    } finally { 
    } 
} 

Answer 2

如果你有類名，ReadFile的

public class ReadFile { 

    public static ReadFile thisCls; 
    private String filename = "C:/Users/D/Documents/Senderlist.csv"; 

    public static ReadFile getSenderClass() 
    { 
     if(thisCls == null) thisCls = new ReadFile(); 

     return thisCls; 
    } 

    private CSVRead() {} 

    public List<String []> readCsv() { 

     try { 
      CSVReader reader = new CSVReader(new FileReader(filename)); 
      // UTF-8 
      // CSVReader reader = new CSVReader(new InputStreamReader(new FileInputStream(filename), "UTF-8"), ",", '"', 1); 
      String[] s; 
      while ((s = reader.readNext()) != null) 
      { 
       data.add(s); 
      } 
     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     return data; 
    } 
} 

然後，你的servlet類可能be

public class MailController extends HttpServlet { 

    .....skip code.... 


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    // read from field 
     List<File> uploadedFiles= saveUploadedFiles(request); 
     String sender=request.getParameter("sender");// reading from the form page 
     String recipient=request.getParameter("recipient"); 
     String subject=request.getParameter("subject"); 
     String content=request.getParameter("content"); 
     //String resultMessage = ""; 
     List<String> resultMessage = new ArrayList<String>(); 

     //<============================== 
     CSVRead read = new CSVRead(); 
     List<String[]> data = CSVRead.readCsv(); 

     //assuming you have a sender in a second column value 
     Iterator<String[]> it = data.iterator(); 

     String targetSender = null; 

     try { 
      String[] array = (String[]) it.next(); 

      targetSender = array[1]; 

      EmailUtility.sendEmail(ExchangeIP, port,sender, recipient, subject, content, uploadedFiles); 

      resultMessage.add("The e-mail has been sent successfully to " + targetSender); 
     } catch (Exception ex) { 
      ex.printStackTrace(); 
      resultMessage.add("There were an error: " + ex.getMessage() + " while sending user " + targetSender); 
     } 


     try{ 
      while (it.hasNext()) { 
       try { 
        String[] array = (String[]) it.next(); 

        targetSender = array[1]; 

        EmailUtility.sendEmail(ExchangeIP, port,targetSender, recipient, subject, content, uploadedFiles); 

        resultMessage.add("The e-mail has been sent successfully to " + targetSender); 
       } catch (Exception ex) { 
        ex.printStackTrace(); 
        resultMessage.add("There were an error: " + ex.getMessage() + " while sending user " + targetSender); 
       } 
      } 
     } finally { 
      //deleteUploadFiles(uploadedFiles); 
      request.setAttribute("Message", resultMessage); 
      getServletContext().getRequestDispatcher("/Result.jsp").forward(request, response); 
     } 

    } 

} 

I d不知道EmailUtility類的sendEmail方法。 我假設第三個參數必須是發件人。