Question

I’m trying to send an email without Gmail and using javax.mail. In particular, I use two files:
mailSender.java and the MainActivity.

mailSender.java:

package com.polito.gmail;

import java.util.Date;
import java.util.Properties;

import javax.activation.CommandMap;
import javax.activation.MailcapCommandMap;
import javax.mail.BodyPart;
import javax.mail.Multipart;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class mailSender extends javax.mail.Authenticator {
    private String _user;
    private String _pass;

    private String[] destAddr = {"[e-mail]", "[e-mail]"};
    private String fromAddr = "[e-mail]";

    private String _port;
    private String _sport;

    private String _host;

    private String _subject = "New Mail";
    private String _body;

    private boolean _auth;

    private boolean _debuggable;

    private Multipart _multipart;

    public mailSender() {
        _host = "smtp.gmail.com"; // default smtp server
        _port = "465"; // default smtp port
        _sport = "465"; // default socketfactory port

        _user = ""; // username
        _pass = ""; // password
        _body = ""; // email body

        _debuggable = false; // debug mode on or off - default off
        _auth = true; // smtp authentication - default on

        _multipart = new MimeMultipart();

        // There is something wrong with MailCap, javamail can not find a
        // handler for the multipart/mixed part, so this bit needs to be added.
        MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
        mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html");
        mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml");
        mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain");
        mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed");
        mc.addMailcap("message/rfc822;; x-java-content-handler=com.sun.mail.handlers.message_rfc822");
        CommandMap.setDefaultCommandMap(mc);
    }

    public mailSender(String user, String pass) {
        this();
        _user = user;
        _pass = pass;
    }

    public boolean send() throws Exception {
        Properties props = _setProperties();

        if (!_user.equals("") && !_pass.equals("") && destAddr.length > 0
                && !fromAddr.equals("") && !_subject.equals("")
                && !_body.equals("")) {
            Session session = Session.getInstance(props, this);

            MimeMessage msg = new MimeMessage(session);

            msg.setFrom(new InternetAddress(fromAddr));

            InternetAddress[] addressTo = new InternetAddress[destAddr.length];
            for (int i = 0; i < destAddr.length; i++) {
                addressTo[i] = new InternetAddress(destAddr[i]);
            }
            msg.setRecipients(MimeMessage.RecipientType.TO, addressTo);

            msg.setSubject(_subject);
            msg.setSentDate(new Date());

            // setup message body
            BodyPart messageBodyPart = new MimeBodyPart();
            messageBodyPart.setText(_body);
            _multipart.addBodyPart(messageBodyPart);

            // Put parts in message
            msg.setContent(_multipart);

            // send email
            Transport.send(msg);

            return true;
        } else {
            return false;
        }
    }

    @Override
    public PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(_user, _pass);
    }

    private Properties _setProperties() {
        Properties props = new Properties();

        props.put("mail.smtp.host", _host);

        if (_debuggable) {
            props.put("mail.debug", "false");
        }

        if (_auth) {
            props.put("mail.smtp.auth", "true");
        }

        props.put("mail.smtp.port", _port);
        props.put("mail.smtp.socketFactory.port", _sport);
        props.put("mail.smtp.socketFactory.class",
                "javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");

        return props;
    }

    // the getters and setters
    public String getBody() {
        return _body;
    }

    public void setBody(String _body) {
        this._body = _body;
    }

In the MainActivity.java:

mailSender sender = new mailSender("[e-mail]","password");
        sender.setBody(prepareBody());
        try {

            if(sender.send()) { 
                    Toast.makeText(MainActivity.this, "Mail send", Toast.LENGTH_LONG).show();
                } else { 
                    Toast.makeText(MainActivity.this, "Mail not send", Toast.LENGTH_LONG).show();
                } 
} catch (Exception e) {
            Log.e("error", String.valueOf(e.getMessage()));
        }

I insert the INTERNET permission in manifest file and i ping correctly smtp.gmail.com, but the application generate this exception:

01-10 11:06:52.238: E/AndroidRuntime(2001): FATAL EXCEPTION: main
01-10 11:06:52.238: E/AndroidRuntime(2001): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.polito.gmail/com.polito.gmail.MainActivity}: java.lang.NullPointerException
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2185)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2210)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread.access$600(ActivityThread.java:142)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1208)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.os.Looper.loop(Looper.java:137)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread.main(ActivityThread.java:4931)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at java.lang.reflect.Method.invokeNative(Native Method)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at java.lang.reflect.Method.invoke(Method.java:511)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at dalvik.system.NativeStart.main(Native Method)
01-10 11:06:52.238: E/AndroidRuntime(2001): Caused by: java.lang.NullPointerException
01-10 11:06:52.238: E/AndroidRuntime(2001):     at com.polito.gmail.MainActivity.onCreate(MainActivity.java:48)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.Activity.performCreate(Activity.java:5008)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
01-10 11:06:52.238: E/AndroidRuntime(2001):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2139)
01-10 11:06:52.238: E/AndroidRuntime(2001):     ... 11 more

What is the problem?

Answer 1

Your code seems correct, check if you’re receiving the mail or not. The exception occurs because there is no message relating to the exception. Try this to avoid the NullPointerException:

Log.e("error", String.valueOf(e));

Update:
For better a logic regarding exception handling using javamail, follow this:

            try {
                sender.send();
               Toast.makeText(MainActivity.this, "Mail send", Toast.LENGTH_LONG).show();
            }
            catch (Exception e) {                   

                if (e.toString().equals("java.lang.NullPointerException"))                      
                    Toast.makeText(MainActivity.this, "Mail not send: Mail settings not configured", Toast.LENGTH_LONG).show();

                else if (e.toString().equals("javax.mail.AuthenticationFailedException"))                       
                    Toast.makeText(MainActivity.this, "Mail not send: Wrong Username or Password", Toast.LENGTH_LONG).show();

                else if (e.toString().equals("Invalid Addresses"))                      
                    Toast.makeText(MainActivity.this, "Mail not send: Invalid Address(es)", Toast.LENGTH_LONG).show();

                else
                    Toast.makeText(MainActivity.this, "Mail not send", Toast.LENGTH_LONG).show();                   

                }