java.lang.ClassNotFoundException: com.csvreader.CsvReader

Question

我正在开发一个应用程序，用于在连续循环中从多个发件人发送大量电子邮件。发送者的电子邮件ID存储在csv文件中，我在ReadFile类中读取它，并在servlet类中调用它，在servlet类中我还调用了一个具有电子邮件发送功能的电子邮件实用程序类。

ReadFile.java

CsvReader senders; 
public List<String> read(){
  ArrayList<String> al=new ArrayList<String>();
  try {
    senders = new CsvReader("C:/Users/dc/Documents/Senderlist.csv");
    senders.readHeaders();

    while (senders.readRecord()) {
      String SenderID = senders.get("SenderID");
      // perform program logic here
      System.out.println("Sender ID is: "+SenderID );
      al.add(SenderID);
    }
    senders.close();
  } catch (FileNotFoundException e) {
    e.printStackTrace();
  } catch (IOException e) {
    e.printStackTrace();
  }
  return al;
}

Servlet.java：

public class MailController extends HttpServlet {
  private static final long serialVersionUID = 1L;
  private String ExchangeIP;
  private String port;
  ReadFile rf;
  /**
   * @throws IOException 
   * @see HttpServlet#HttpServlet()
   */
  public MailController() throws IOException {
    rf=new ReadFile();
  }

  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 {
    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 = ""; //null
    try {
      List sendersInput = rf.read();
      // print all the elements in the list 
      Iterator itr = sendersInput.iterator();
      while(itr.hasNext()) {
        EmailUtility.sendEmail(ExchangeIP, port, itr.next(), 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 {
      request.setAttribute("Message", resultMessage);
      getServletContext()
        .getRequestDispatcher("/Result.jsp")
        .forward(request, response);
    }   
  }
}

运行此命令时，我收到一个错误：

java.lang.ClassNotFoundException: com.csvreader.CsvReader
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1702)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
    at com.project.util.ReadFile.read(ReadFile.java:20)
    at com.project.controller.MailController.doPost(MailController.java:99)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

如何解决此错误。

Answer 1

你错过了opencsv.jar库。在java命令中使用以下命令指定它

java -cp opencsv.jar:...

Answer 2

通过将apache tomcat库中的servlet-api.jar添加到projects->properties->java构建路径中，解决了这个错误。