java.lang.NumberFormatException : For input string: "null" while trying to send an email using netbeans

Question

我正在尝试在 netbeans 中创建一个电子邮件客户端来发送电子邮件，但我在代码中遇到了 numberformatexception。这是我的代码(共有三个类):

EmailClient.java

package sendemail;

    public class EmailClient extends javax.swing.JFrame {

        SendMail sm=new SendMail();
        Settings set=new Settings();
        public EmailClient() {
            initComponents();
        }


        @SuppressWarnings("unchecked")
        +Generated code                     

        private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
           // TODO add your handling code here:
            sm.setVisible(true);
        }                                        

        private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            // TODO add your handling code here:
        }                                        

        private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            // TODO add your handling code here:
        }                                        

        private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
            // TODO add your handling code here:
            set.setVisible(true);
        }                                          

        public static void main(String args[]) {
            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                @Override
                public void run() {
                    new EmailClient().setVisible(true);
                }
            });
        }

        // Variables declaration - do not modify                     
        private javax.swing.JButton jButton1;
        private javax.swing.JButton jButton2;
        private javax.swing.JButton jButton3;
        private javax.swing.JLabel jLabel1;
        private javax.swing.JLabel jLabel2;
        private javax.swing.JLabel jLabel3;
        private javax.swing.JLabel jLabel4;
        private javax.swing.JLabel jLabel5;
        private javax.swing.JLabel jLabel6;
        private javax.swing.JMenu jMenu4;
        private javax.swing.JMenu jMenu5;
        private javax.swing.JMenuBar jMenuBar2;
        private javax.swing.JMenuItem jMenuItem2;
        private javax.swing.JPanel jPanel1;
        private javax.swing.JPanel jPanel3;
        private javax.swing.JPanel jPanel4;
        private javax.swing.JScrollPane jScrollPane1;
        private javax.swing.JTextArea jTextArea1;
        // End of variables declaration                   
    }

Settings.java

    package sendemail;
    import javax.swing.*;
    import java.awt.*;

    public class Settings extends javax.swing.JFrame {

        public String uname;
        public String pass;
        public String smtpserver;
        public String  port;
        /**
         * Creates new form Settings
         */
        public Settings() {
            initComponents();
        }

        public String getUname() {
            return uname;
        }

        public String getPass() {
            return pass;
        }

        public String getSmtpserver() {
            return smtpserver;
        }

        public String getPort() {
            return port;
        }



        @SuppressWarnings("unchecked")
        +Generated Code                   

        private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            // TODO add your handling code here:
           uname=jTextField1.getText().toString();
            pass=jPasswordField1.getPassword().toString();

            smtpserver=jComboBox1.getSelectedItem().toString();
            port=jComboBox2.getSelectedItem().toString();

            if(uname.equals("") || pass.equals("") || smtpserver.equals("") || port.equals("") )
        {
                JOptionPane.showMessageDialog(this,"All Fields are mandatory");
        }                                        
        else
            {
                setVisible(false);
            }

        }                                        

        private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
            // TODO add your handling code here:
        }                                          

        public static void main(String args[]) {
            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new Settings().setVisible(false);
                }
            });
        }

        // Variables declaration - do not modify                     
        private javax.swing.JButton jButton1;
        private javax.swing.JComboBox jComboBox1;
        private javax.swing.JComboBox jComboBox2;
        private javax.swing.JLabel jLabel1;
        private javax.swing.JLabel jLabel2;
        private javax.swing.JLabel jLabel3;
        private javax.swing.JLabel jLabel4;
        private javax.swing.JPanel jPanel1;
        private javax.swing.JPasswordField jPasswordField1;
        private javax.swing.JTextField jTextField1;
        // End of variables declaration                   

    }

SendMail.Java

package sendemail;

    import java.util.Properties;
    import javax.mail.Message;
    import javax.mail.Session;
    import javax.mail.Transport;
    import javax.mail.internet.InternetAddress;
    import javax.mail.internet.MimeMessage;
    import javax.swing.JOptionPane;
    import java.awt.*;
    import javax.mail.*;
    import javax.mail.MessagingException;


    public class SendMail extends javax.swing.JFrame {

        Settings setfrm=new Settings();
        String subject;
        String from;

        public SendMail() {
            initComponents();
        }


        @SuppressWarnings("unchecked")
        +Generated Code                    

        private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            // TODO add your handling code here:
            try
            {
            final String user=setfrm.getUname();
            final String password=setfrm.getPass();
            String portnum=setfrm.getPort();
            String smtpname=setfrm.getSmtpserver();
            String to=jTextField1.getText();
            subject=jTextField2.getText();
            Properties properties=new Properties();
            properties.put("mail.smtp.host",smtpname.toString());
            properties.put("mail.smtp.socketFactory.port",portnum.toString());
            properties.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
            properties.put("mail.smtp.port",portnum.toString());
            properties.put("mail.smtp.auth","true");
            Session session=Session.getDefaultInstance(properties,
               new javax.mail.Authenticator() {
                   protected PasswordAuthentication getPasswordAuthentication(){
                    return new PasswordAuthentication(user,password);

               }

               }

               );
            MimeMessage message=new MimeMessage(session);
            message.setFrom(new InternetAddress(user));
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(jTextField1.getText().toString()));
            message.setSubject(subject);
            message.setText(jTextArea1.getText());
            Transport.send(message);
            JOptionPane.showMessageDialog(null,"message sent");
            }
            catch(MessagingException mex)
            {
                JOptionPane.showMessageDialog(null,mex);
            }
        }                                        

        private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            // TODO add your handling code here:
        }                                        

        private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {                                            
            // TODO add your handling code here:
        }                                           

        public static void main(String args[]) {
            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new SendMail().setVisible(true);
                }
            });
        }

        // Variables declaration - do not modify                     
        private javax.swing.JButton jButton1;
        private javax.swing.JButton jButton2;
        private javax.swing.JLabel jLabel1;
        private javax.swing.JLabel jLabel2;
        private javax.swing.JPanel jPanel1;
        private javax.swing.JScrollPane jScrollPane1;
        private javax.swing.JTextArea jTextArea1;
        private javax.swing.JTextField jTextField1;
        private javax.swing.JTextField jTextField2;
        // End of variables declaration                   

    }

错误:

java.lang.NumberFormatException: For input string: "null"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:492)
        at java.lang.Integer.parseInt(Integer.java:527)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:145)
        at javax.mail.Service.connect(Service.java:297)
        at javax.mail.Service.connect(Service.java:156)
        at javax.mail.Service.connect(Service.java:105)
        at com.sun.mail.smtp.SMTPTransport.connect(SMTPTransport.java:93)
        at javax.mail.Transport.send0(Transport.java:168)
        at javax.mail.Transport.send(Transport.java:98)
        at sendemail.SendMail.jButton1ActionPerformed(SendMail.java:177)
        at sendemail.SendMail.access$100(SendMail.java:25)
        at sendemail.SendMail$2.actionPerformed(SendMail.java:77)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
        at java.awt.Component.processMouseEvent(Component.java:6505)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3311)
        at java.awt.Component.processEvent(Component.java:6270)
        at java.awt.Container.processEvent(Container.java:2229)
        at java.awt.Component.dispatchEventImpl(Component.java:4861)
        at java.awt.Container.dispatchEventImpl(Container.java:2287)
        at java.awt.Component.dispatchEvent(Component.java:4687)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
        at java.awt.Container.dispatchEventImpl(Container.java:2273)
        at java.awt.Window.dispatchEventImpl(Window.java:2719)
        at java.awt.Component.dispatchEvent(Component.java:4687)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
        at java.awt.EventQueue.access$200(EventQueue.java:103)
        at java.awt.EventQueue$3.run(EventQueue.java:694)
        at java.awt.EventQueue$3.run(EventQueue.java:692)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
        at java.awt.EventQueue$4.run(EventQueue.java:708)
        at java.awt.EventQueue$4.run(EventQueue.java:706)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
    BUILD STOPPED (total time: 1 minute 2 seconds)

我尝试使用 SendMail.java 发送电子邮件，而发件人的电子邮件和密码是从 Settings.java 输入的，而 EmailClient.java 仅用于在单击按钮时将 JFrames 可见性设置为 true 或 false .

Answer 1

java.lang.NumberFormatException: For input string: “null”

据我所知，当您尝试发送电子邮件时，唯一可以解析为数字的字段(并给您这样的异常(exception))是端口号。话虽如此，您可以在此处从 Settings 类的组合框中选择端口号:

port = jComboBox2.getSelectedItem().toString();

并在此处的 SendEmail 类的属性中设置此端口号:

String portnum = setfrm.getPort();
...
Properties properties = new Properties();
...
properties.put("mail.smtp.port", portnum.toString());

在您的代码中，您没有向组合框添加任何对象。至少你没有显示该部分，但你必须在某个地方这样做，否则你会在这里得到一个 NullPointerException :

port = jComboBox2.getSelectedItem().toString();

但是，port 可能会保存 "null" 字符串，因此以下调用会引发异常:

Integer.parseInt("null"); // called somewhere within com.sun.mail.smtp.SMTPTransport.protocolConnect() method