Java Mail Sending

Principle of E-mail Sending

We write to pen pals:

Write a letter - > Put it in the mailbox - > pick it up at the local post office - > Pass it to the post office where the recipient is located - > Put the envelope in the mailbox of the recipient's family - > Pen pal gets the letter in the mailbox - > Read the letter

Similarly, when we send e-mail to others, we also need an e-mail office, that is, mail server. The qq mailbox and Netease mailbox we use are like mailboxes for sending envelopes.

Mail Server

• SMTP Server (Mail Sender): Server that handles user mail send (smtp) requests

  The address of the SMTP server is generally smtp.xxx.com，For example, the QQ mailbox is smtp.qq.com..

• POP3 Server (Mail Receiving Server): Server that handles user mail receiving (pop3) requests

Example: I want to send an email to my Netease mailbox (aaa@163.com) through my QQ mailbox (0000000000@qq.com).

Sending mail in Java

First we need to prepare the JavaMail API and the Java Activation Framework.

Get two jar packages:

• mail.jar
• activation.jar

JavaMail is a standard development package provided by Sun Company to facilitate Java developers to implement mail sending and receiving functions in applications. It supports common mail protocols, such as SMTP, POP3, etc.

Because I use qq mailbox, to get the permission of qq mailbox, I will get an authorization code.

Remember the authorization code.

Guide Pack

Send text only

package priv.sehun.mail;

import com.sun.mail.util.MailSSLSocketFactory;

import java.security.GeneralSecurityException;
import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;


public class SendMail {
    public static void main(String[] args) throws GeneralSecurityException, MessagingException {

        Properties properties = new Properties();
        properties.setProperty("mail.host", "smtp.qq.com");
        properties.setProperty("mail.transport.protocol", "smtp");
        properties.setProperty("mail.smtp.auth", "true");

        //QQ mailbox to set up SSL encryption, fixed code
        MailSSLSocketFactory sf = new MailSSLSocketFactory();
        sf.setTrustAllHosts(true);
        properties.put("mail.smtp.ssl.enable", "true");
        properties.put("mail.smtp.ssl.socketFactory", sf);



        Session session = Session.getDefaultInstance(properties, new Authenticator() {
            public PasswordAuthentication getPasswordAuthentication() {
                //Sender mail username, authorization code
                return new PasswordAuthentication("15********@qq.com", "Your own authorization code");
            }
        });


        //1. Open Session's debug mode so that you can see the running status of the program sending Email.
        session.setDebug(true);


        Transport ts = session.getTransport();

        //Connect to mail server using mailbox username and authorization code
        ts.connect("smtp.qq.com", "15********@qq.com", "Your own authorization code");



        //Create mail objects
        MimeMessage message = new MimeMessage(session);

        //Identify the sender of the mail
        message.setFrom(new InternetAddress("15********@qq.com"));

        //Identify the recipient of the mail
        message.setRecipient(Message.RecipientType.TO, new InternetAddress("12********@qq.com"));

        //Title of mail
        message.setSubject("Good morning, cp");

        //Text content of mail
        message.setContent("You have to be happy.^-^", "text/html;charset=UTF-8");

        //Send mail
        ts.sendMessage(message, message.getAllRecipients());

        ts.close();
    }
}

Send mail with pictures and attachments

package priv.sehun.mail;

import com.sun.mail.util.MailSSLSocketFactory;

import java.security.GeneralSecurityException;
import java.util.*;
import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.*;

public class SendMail2 {
    public static void main(String[] args) throws GeneralSecurityException, MessagingException {
        Properties properties = new Properties();
        properties.setProperty("mail.host", "smtp.qq.com");
        properties.setProperty("mail.transport.protocol", "smtp");
        properties.setProperty("mail.smtp.auth", "true");


        MailSSLSocketFactory sf = new MailSSLSocketFactory();
        sf.setTrustAllHosts(true);
        properties.put("mail.smtp.ssl.enable", "true");
        properties.put("mail.smtp.ssl.socketFactory", sf);



        Session session = Session.getDefaultInstance(properties, new Authenticator() {
            public PasswordAuthentication getPasswordAuthentication() {
                //Sender mail username, authorization code
                return new PasswordAuthentication("15********@qq.com", "Authorization code");
            }
        });


        //Open Session's debug mode so that you can see the running status of the program sending Email
        session.setDebug(true);


        Transport ts = session.getTransport();

        //Connect to mail server using mailbox username and authorization code
        ts.connect("smtp.qq.com", "15********@qq.com", "Authorization code");



        //Create mail objects
        MimeMessage message = getMimeMessage(session);


        //Send mail
        ts.sendMessage(message, message.getAllRecipients());

        ts.close();
    }

    private static MimeMessage getMimeMessage(Session session) throws MessagingException {
        MimeMessage message = new MimeMessage(session);

        //Identify the sender of the mail
        message.setFrom(new InternetAddress("15********@qq.com"));

        //Identify the recipient of the mail
        message.setRecipient(Message.RecipientType.TO, new InternetAddress("26********@qq.com"));

        //Title of mail
        message.setSubject("I am an email with pictures and attachments.");


        //picture
        MimeBodyPart body1 = new MimeBodyPart();
        body1.setDataHandler(new DataHandler(new FileDataSource("src/resources/bjyx.png")));
        body1.setContentID("yhbxb.png"); //Picture Setup ID

        //text
        MimeBodyPart body2 = new MimeBodyPart();
        body2.setContent("Good morning<img src='cid:yhbxb.png'>","text/html;charset=utf-8");

        //Enclosure
        MimeBodyPart body3 = new MimeBodyPart();
        body3.setDataHandler(new DataHandler(new FileDataSource("src/resources/peace.properties")));
        body3.setFileName("peace.properties"); 

        MimeBodyPart body4 = new MimeBodyPart();
        body4.setDataHandler(new DataHandler(new FileDataSource("src/resources/love.txt")));
        body4.setFileName("love.txt"); 

        //Stitching Pictures and Texts
        MimeMultipart multipart1 = new MimeMultipart();
        multipart1.addBodyPart(body1);
        multipart1.addBodyPart(body2);
        multipart1.setSubType("related");

        
        MimeBodyPart mbody =  new MimeBodyPart();
        mbody.setContent(multipart1);

        //Stitching accessories
        MimeMultipart multipart2 =new MimeMultipart();
        multipart2.addBodyPart(body3);
        multipart2.addBodyPart(body4);
        multipart2.addBodyPart(mbody);
        multipart2.setSubType("mixed"); 


        //Put it in a Message message
        message.setContent(multipart2);
        //Save Modifications
        message.saveChanges();

        return message;

    }

}

Sending mail in conjunction with Java Web

Write a registration page and send the user registration information to the user's e-mail.

The results are as follows.

Code

Entity class: User.java

package priv.sehun.pojo;

public class User {
    private String username;
    private String password;
    private String email;

    public User() {
    }

    public User(String username, String password, String email) {
        this.username = username;
        this.password = password;
        this.email = email;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

** Front-end Registration: ** register.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <style>
        
        h1{
            color: coral;
            align-content: center;
        }
        form{
            align-content: center;
        }
        
    </style>
</head>
<body>
<h1>Welcome to Pineapple Registration Page</h1>
<form action="${pageContext.request.contextPath}/send" method="post">

    User name:<p><input type="text" name="username" required></p>
    Password:<p><input type="password" name="password" required></p>
    Your mailbox:<p><input type="text" name="email" required></p>
    <input type="submit" value="register">

</form>

</body>
</html>

Tool class for sending mail:

package priv.sehun.utils;

import priv.sehun.pojo.User;


import java.util.Properties;
import com.sun.mail.util.MailSSLSocketFactory;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;


public class SendMail extends Thread {
    //Website mailbox (used to send registration information to users of registered websites)
    private String addresserMailbox ="1597621711@qq.com";
    //Mailbox username
    private String username = "1597621711@qq.com";
    //Website Mailbox Authorization Code/Password
    private String addresserPassword = "lohbdcweihwvhhhb";
    //Server address for sending mail
    private String host = "smtp.qq.com";


    //User Information
    private User user;
    public SendMail(User user){
        this.user = user;
    }


    @Override
    public void run() {

        try {
            Properties properties = new Properties();
            properties.setProperty("mail.host", host);
            properties.setProperty("mail.transport.protocol", "smtp");
            properties.setProperty("mail.smtp.auth", "true");
            MailSSLSocketFactory sf = null;
            sf = new MailSSLSocketFactory();
            properties.put("mail.smtp.ssl.enable", "true");
            properties.put("mail.smtp.ssl.socketFactory", sf);

            Session session = Session.getDefaultInstance(properties, new Authenticator() {
                public PasswordAuthentication getPasswordAuthentication() {
                    //Sender mail username, authorization code
                    return new PasswordAuthentication(addresserMailbox, addresserPassword);
                }
            });

            //Open Session's debug mode so that you can see the running status of the program sending Email
            session.setDebug(true);

            //Get the transport object through session
            Transport ts = session.getTransport();

            //Connect to mail server using mailbox username and authorization code
            ts.connect(host, username, addresserPassword);

            //4. Create mail
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress(addresserMailbox)); //Sender (website mailbox)
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(user.getEmail())); //Recipient (user mailbox)
            message.setSubject("User Registration Mail"); //Title of mail

            String info = "Congratulations on your successful registration^-^"
                    +"\n Your user name is:" + user.getUsername()
                    + "\n Your password is:" + user.getPassword() + "\n Please take good care of it.,Our website has no way to retrieve registration information";

            message.setContent(info, "text/html;charset=UTF-8");
            message.saveChanges();

            //Send mail
            ts.sendMessage(message, message.getAllRecipients());
            ts.close();


        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Corresponding Servlet: RegisterServlet.java

package priv.sehun.servlet;

import priv.sehun.pojo.User;
import priv.sehun.utils.SendMail;

import java.io.IOException;

public class RegisterServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        try {
            //Receiving user requests and encapsulating them as objects
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            String email = request.getParameter("email");
            User user = new User(username,password,email);

            //After the user registers successfully, send an email to the user
            //We use threads to send mail specially to prevent time-consuming and excessive number of registered websites.
            SendMail send = new SendMail(user);
            //Start the thread, and after the thread starts, it executes the run method to send mail.
            send.start();

            //Registered User
            request.setAttribute("message", "login was successful!We have sent registration information to your mailbox. Please check it carefully.");
            request.getRequestDispatcher("info.jsp").forward(request, response);
        } catch (Exception e) {
            e.printStackTrace();
            request.setAttribute("message", "Registration failed!!");
            request.getRequestDispatcher("info.jsp").forward(request, response);
        }
    }
}