无法从Java Web应用程序发送电子邮件

我无法使用以下代码发送电子邮件。我的图书馆里有所有需要的罐子。我在mysql workbench上连接了一个数据库，我从表单action=“EmailListServlet”中提取数据，并从数据库中获取用户详细信息。即使我能够在netbeans的输出窗口中接收输出，我也会收到catch块中的异常消息

EmailListServlet

@WebServlet(name = "EmailListServlet", urlPatterns = {"/EmailListServlet"})
public class EmailListServlet extends HttpServlet {

    @EJB
    private EmailSenderBean sendMail;

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        HttpSession session = request.getSession(true);
        session.setMaxInactiveInterval(-1);
        String url ="";

        EntityManager em = DBUtil.getEmFactory().createEntityManager();
        User user= (User) session.getAttribute("theUser");
        String name = request.getParameter("Name");
        System.out.println("Name is"+name);
        String fromEmail = request.getParameter("User_Id");
        System.out.println("Sender Email is"+fromEmail);
        String toEmail = request.getParameter("Friend_Id");
        System.out.println("To Email is"+toEmail);
        String message = request.getParameter("Message");
        System.out.println("Message is"+message);
        fromEmail = "'"+fromEmail+"'";
        String userPwd = user.getPassword();
        System.out.println("Password is" +userPwd);

        try{
            sendMail.SendEmail(name, fromEmail, userPwd, toEmail, message);
            url="/confirmr.jsp";
        }
        catch(Exception e){
            System.out.println("This is an Exception");
        }

        em.close();
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}

---

这指向sendMail.sendMail（名称、fromEmail、userPwd、toEmail、message）

两天后，我终于可以运行这段代码了。我的更新代码在下面分享

EmailSenderBean.java

public class EmailSenderBean {

// Add business logic below. (Right-click in editor and choose
// "Insert Code > Add Business Method")

public void sendEmail(String name, String fromEmail, String toEmail, String subject, String message) {

    Properties props = System.getProperties();

    props.put("mail.smtp.port", "587");
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.starttls.enable", "true");

    String [] toEmails = {toEmail};
    String emailSubject = subject;
String emailBody = message;

    Session session = Session.getDefaultInstance(props, null);
    Message mailMessage = new MimeMessage(session);

    try {
        String fromUser = "youremailid@gmail.com";
        String fromUserEmailPassword = "yourpassword";

        if(fromEmail!=null && !fromEmail.trim().equals("")){
            mailMessage.setFrom(new InternetAddress(fromEmail));
        }
        else{
            mailMessage.setFrom(new InternetAddress(fromUser));
        }
        for (String toEmail1 : toEmails) {
            mailMessage.addRecipient(Message.RecipientType.TO, new InternetAddress(toEmail1));
        }
        mailMessage.setSubject(emailSubject);
        mailMessage.setContent(emailBody, "text/html");

        String emailHost = "smtp.gmail.com";
        Transport transport = session.getTransport("smtp");
        transport.connect(emailHost, fromUser, fromUserEmailPassword);
        transport.sendMessage(mailMessage, mailMessage.getAllRecipients());
        transport.close();
    }
    catch(AddressException ex){
        ex.printStackTrace();
        Logger.getLogger(EmailSenderBean.class.getName()).log(Level.SEVERE, null, ex);
    }
    catch (MessagingException ex) {
        ex.printStackTrace();
        Logger.getLogger(EmailSenderBean.class.getName()).log(Level.SEVERE, null, ex);
    }

}
}

EmailListServlet.java

@WebServlet(name = "EmailListServlet", urlPatterns = {"/EmailListServlet"})
public class EmailListServlet extends HttpServlet {


public EmailSenderBean sendMail;

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    doPost(request, response);
}

/**
 * Handles the HTTP <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    String url="";
    response.setContentType("text/html;charset=UTF-8");

    EntityManager em = DBUtil.getEmFactory().createEntityManager();

    String action  = request.getParameter("action");
    String name = request.getParameter("Name");
    String fromEmail = request.getParameter("User_Id");
    String toEmail = request.getParameter("Friend_Id");
    String message = request.getParameter("Message");


    sendMail = new EmailSenderBean();

    String subject ="";
    if(action.equals("contact")){
        subject = "Contact made via ORNSurveys";
        message = name+" wants to contact you via ORN SURVEYS"+message;
        sendMail.sendEmail(name, null, toEmail, subject, message);
        url = "/confirmc.jsp";
    }else if(action.equals("recommend")){
        subject = "Recommendation to join ORNSurveys";
        message = name+" wants to recommend you to join ORN SURVEYS"+message;
        sendMail.sendEmail(name, fromEmail, toEmail, subject, message);
        url = "/confirmr.jsp";
    }
    em.close();
    getServletContext()
            .getRequestDispatcher(url)
            .forward(request, response);

}
}

---

为了让回答者或其他有类似问题的人更容易回答，请添加一个特定的问题陈述——“它不起作用”，可以假设，但它怎么不起作用呢？什么错误消息或错误行为是特征？给我们一个堆栈跟踪？还有System.out.println（“这是一个异常”）；-这是horrible@NathanTuggy，我得到NullPointerException。当我试图打印表单和数据库中的变量时，我能够打印它们，但是当我试图将其发送到Bean时，它抛出NullPointerException，您读过了吗？

@WebServlet(name = "EmailListServlet", urlPatterns = {"/EmailListServlet"})
public class EmailListServlet extends HttpServlet {


public EmailSenderBean sendMail;

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    doPost(request, response);
}

/**
 * Handles the HTTP <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    String url="";
    response.setContentType("text/html;charset=UTF-8");

    EntityManager em = DBUtil.getEmFactory().createEntityManager();

    String action  = request.getParameter("action");
    String name = request.getParameter("Name");
    String fromEmail = request.getParameter("User_Id");
    String toEmail = request.getParameter("Friend_Id");
    String message = request.getParameter("Message");


    sendMail = new EmailSenderBean();

    String subject ="";
    if(action.equals("contact")){
        subject = "Contact made via ORNSurveys";
        message = name+" wants to contact you via ORN SURVEYS"+message;
        sendMail.sendEmail(name, null, toEmail, subject, message);
        url = "/confirmc.jsp";
    }else if(action.equals("recommend")){
        subject = "Recommendation to join ORNSurveys";
        message = name+" wants to recommend you to join ORN SURVEYS"+message;
        sendMail.sendEmail(name, fromEmail, toEmail, subject, message);
        url = "/confirmr.jsp";
    }
    em.close();
    getServletContext()
            .getRequestDispatcher(url)
            .forward(request, response);

}
}