使用 Java 发送电子邮件

email java

2022-08-31 08:40:47

我正在尝试使用 Java 发送电子邮件：

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class SendEmail {

   public static void main(String [] args) {

      // Recipient's email ID needs to be mentioned.
      String to = "abcd@example.com";

      // Sender's email ID needs to be mentioned
      String from = "web@example.com";

      // Assuming you are sending email from localhost
      String host = "localhost";

      // Get system properties
      Properties properties = System.getProperties();

      // Setup mail server
      properties.setProperty("mail.smtp.host", host);

      // Get the default Session object.
      Session session = Session.getDefaultInstance(properties);

      try{
         // Create a default MimeMessage object.
         MimeMessage message = new MimeMessage(session);

         // Set From: header field of the header.
         message.setFrom(new InternetAddress(from));

         // Set To: header field of the header.
         message.addRecipient(Message.RecipientType.TO,
                                  new InternetAddress(to));

         // Set Subject: header field
         message.setSubject("This is the Subject Line!");

         // Now set the actual message
         message.setText("This is actual message");

         // Send message
         Transport.send(message);
         System.out.println("Sent message successfully....");
      }catch (MessagingException mex) {
         mex.printStackTrace();
      }
   }
}

我收到错误：

javax.mail.MessagingException: Could not connect to SMTP host: localhost, port: 25;
  nested exception is:java.net.ConnectException: Connection refused: connect
        at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1706)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:525)

此代码是否适用于发送电子邮件？

答案 1

以下代码与谷歌SMTP服务器配合得很好。您需要提供您的 Google 用户名和密码。

import com.sun.mail.smtp.SMTPTransport;
import java.security.Security;
import java.util.Date;
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

/**
 *
 * @author doraemon
 */
public class GoogleMail {
    private GoogleMail() {
    }

    /**
     * Send email using GMail SMTP server.
     *
     * @param username GMail username
     * @param password GMail password
     * @param recipientEmail TO recipient
     * @param title title of the message
     * @param message message to be sent
     * @throws AddressException if the email address parse failed
     * @throws MessagingException if the connection is dead or not in the connected state or if the message is not a MimeMessage
     */
    public static void Send(final String username, final String password, String recipientEmail, String title, String message) throws AddressException, MessagingException {
        GoogleMail.Send(username, password, recipientEmail, "", title, message);
    }

    /**
     * Send email using GMail SMTP server.
     *
     * @param username GMail username
     * @param password GMail password
     * @param recipientEmail TO recipient
     * @param ccEmail CC recipient. Can be empty if there is no CC recipient
     * @param title title of the message
     * @param message message to be sent
     * @throws AddressException if the email address parse failed
     * @throws MessagingException if the connection is dead or not in the connected state or if the message is not a MimeMessage
     */
    public static void Send(final String username, final String password, String recipientEmail, String ccEmail, String title, String message) throws AddressException, MessagingException {
        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
        final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";

        // Get a Properties object
        Properties props = System.getProperties();
        props.setProperty("mail.smtps.host", "smtp.gmail.com");
        props.setProperty("mail.smtp.socketFactory.class", SSL_FACTORY);
        props.setProperty("mail.smtp.socketFactory.fallback", "false");
        props.setProperty("mail.smtp.port", "465");
        props.setProperty("mail.smtp.socketFactory.port", "465");
        props.setProperty("mail.smtps.auth", "true");

        /*
        If set to false, the QUIT command is sent and the connection is immediately closed. If set 
        to true (the default), causes the transport to wait for the response to the QUIT command.

        ref :   http://java.sun.com/products/javamail/javadocs/com/sun/mail/smtp/package-summary.html
                http://forum.java.sun.com/thread.jspa?threadID=5205249
                smtpsend.java - demo program from javamail
        */
        props.put("mail.smtps.quitwait", "false");

        Session session = Session.getInstance(props, null);

        // -- Create a new message --
        final MimeMessage msg = new MimeMessage(session);

        // -- Set the FROM and TO fields --
        msg.setFrom(new InternetAddress(username + "@gmail.com"));
        msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipientEmail, false));

        if (ccEmail.length() > 0) {
            msg.setRecipients(Message.RecipientType.CC, InternetAddress.parse(ccEmail, false));
        }

        msg.setSubject(title);
        msg.setText(message, "utf-8");
        msg.setSentDate(new Date());

        SMTPTransport t = (SMTPTransport)session.getTransport("smtps");

        t.connect("smtp.gmail.com", username, password);
        t.sendMessage(msg, msg.getAllRecipients());      
        t.close();
    }
}

2015年12月11日更新

用户名 + 密码不再是推荐的解决方案。这是由于

我尝试了一下，Gmail向此代码中用作用户名的电子邮件发送了一封电子邮件，说我们最近阻止了对您的Google帐户的登录尝试，并将我定向到此支持页面：support.google.com/accounts/answer/6010255 因此它正在寻找它才能正常工作，用于发送的电子邮件帐户需要降低自己的安全性

谷歌发布了Gmail API - https://developers.google.com/gmail/api/?hl=en。我们应该使用oAuth2方法，而不是用户名+密码。

下面是用于使用 Gmail API 的代码段。

谷歌邮件.java

import com.google.api.client.util.Base64;
import com.google.api.services.gmail.Gmail;
import com.google.api.services.gmail.model.Message;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Properties;

import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

/**
 *
 * @author doraemon
 */
public class GoogleMail {
    private GoogleMail() {
    }

    private static MimeMessage createEmail(String to, String cc, String from, String subject, String bodyText) throws MessagingException {
        Properties props = new Properties();
        Session session = Session.getDefaultInstance(props, null);

        MimeMessage email = new MimeMessage(session);
        InternetAddress tAddress = new InternetAddress(to);
        InternetAddress cAddress = cc.isEmpty() ? null : new InternetAddress(cc);
        InternetAddress fAddress = new InternetAddress(from);

        email.setFrom(fAddress);
        if (cAddress != null) {
            email.addRecipient(javax.mail.Message.RecipientType.CC, cAddress);
        }
        email.addRecipient(javax.mail.Message.RecipientType.TO, tAddress);
        email.setSubject(subject);
        email.setText(bodyText);
        return email;
    }

    private static Message createMessageWithEmail(MimeMessage email) throws MessagingException, IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        email.writeTo(baos);
        String encodedEmail = Base64.encodeBase64URLSafeString(baos.toByteArray());
        Message message = new Message();
        message.setRaw(encodedEmail);
        return message;
    }

    public static void Send(Gmail service, String recipientEmail, String ccEmail, String fromEmail, String title, String message) throws IOException, MessagingException {
        Message m = createMessageWithEmail(createEmail(recipientEmail, ccEmail, fromEmail, title, message));
        service.users().messages().send("me", m).execute();
    }
}

要通过 oAuth2 构建授权的 Gmail 服务，下面是代码段。

功利.java

import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.client.util.store.FileDataStoreFactory;
import com.google.api.services.gmail.Gmail;
import com.google.api.services.gmail.GmailScopes;
import com.google.api.services.oauth2.Oauth2;
import com.google.api.services.oauth2.model.Userinfoplus;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.GeneralSecurityException;
import java.util.HashSet;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.yccheok.jstock.engine.Pair;

/**
 *
 * @author yccheok
 */
public class Utils {
    /** Global instance of the JSON factory. */
    private static final GsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();

    /** Global instance of the HTTP transport. */
    private static HttpTransport httpTransport;

    private static final Log log = LogFactory.getLog(Utils.class);

    static {
        try {
            // initialize the transport
            httpTransport = GoogleNetHttpTransport.newTrustedTransport();

        } catch (IOException ex) {
            log.error(null, ex);
        } catch (GeneralSecurityException ex) {
            log.error(null, ex);
        }
    }

    private static File getGmailDataDirectory() {
        return new File(org.yccheok.jstock.gui.Utils.getUserDataDirectory() + "authentication" + File.separator + "gmail");
    }

    /**
     * Send a request to the UserInfo API to retrieve the user's information.
     *
     * @param credentials OAuth 2.0 credentials to authorize the request.
     * @return User's information.
     * @throws java.io.IOException
     */
    public static Userinfoplus getUserInfo(Credential credentials) throws IOException
    {
        Oauth2 userInfoService =
            new Oauth2.Builder(httpTransport, JSON_FACTORY, credentials).setApplicationName("JStock").build();
        Userinfoplus userInfo  = userInfoService.userinfo().get().execute();
        return userInfo;
    }

    public static String loadEmail(File dataStoreDirectory)  {
        File file = new File(dataStoreDirectory, "email");
        try {
            return new String(Files.readAllBytes(Paths.get(file.toURI())), "UTF-8");
        } catch (IOException ex) {
            log.error(null, ex);
            return null;
        }
    }

    public static boolean saveEmail(File dataStoreDirectory, String email) {
        File file = new File(dataStoreDirectory, "email");
        try {
            //If the constructor throws an exception, the finally block will NOT execute
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF-8"));
            try {
                writer.write(email);
            } finally {
                writer.close();
            }
            return true;
        } catch (IOException ex){
            log.error(null, ex);
            return false;
        }
    }

    public static void logoutGmail() {
        File credential = new File(getGmailDataDirectory(), "StoredCredential");
        File email = new File(getGmailDataDirectory(), "email");
        credential.delete();
        email.delete();
    }

    public static Pair<Pair<Credential, String>, Boolean> authorizeGmail() throws Exception {
        // Ask for only the permissions you need. Asking for more permissions will
        // reduce the number of users who finish the process for giving you access
        // to their accounts. It will also increase the amount of effort you will
        // have to spend explaining to users what you are doing with their data.
        // Here we are listing all of the available scopes. You should remove scopes
        // that you are not actually using.
        Set<String> scopes = new HashSet<>();

        // We would like to display what email this credential associated to.
        scopes.add("email");

        scopes.add(GmailScopes.GMAIL_SEND);

        // load client secrets
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(Utils.JSON_FACTORY,
            new InputStreamReader(Utils.class.getResourceAsStream("/assets/authentication/gmail/client_secrets.json")));

        return authorize(clientSecrets, scopes, getGmailDataDirectory());
    }

    /** Authorizes the installed application to access user's protected data.
     * @return 
     * @throws java.lang.Exception */
    private static Pair<Pair<Credential, String>, Boolean> authorize(GoogleClientSecrets clientSecrets, Set<String> scopes, File dataStoreDirectory) throws Exception {
        // Set up authorization code flow.

        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
            httpTransport, JSON_FACTORY, clientSecrets, scopes)
            .setDataStoreFactory(new FileDataStoreFactory(dataStoreDirectory))
            .build();
        // authorize
        return new MyAuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
    }

    public static Gmail getGmail(Credential credential) {
        Gmail service = new Gmail.Builder(httpTransport, JSON_FACTORY, credential).setApplicationName("JStock").build();
        return service;        
    }
}

为了提供一种用户友好的oAuth2身份验证方式，我使用了JavaFX，以显示以下输入对话框

显示用户友好的oAuth2对话框的键可以在MyAuthorizationCodeInstalledApp.java和SimpleSwingBrowser中找到.java

答案 2

以下代码对我有用。

import java.io.UnsupportedEncodingException;
import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendMail {

    public static void main(String[] args) {

        final String username = "your_user_name@gmail.com";
        final String password = "yourpassword";

        Properties props = new Properties();
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
          });

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("your_user_name@gmail.com"));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse("to_email_address@example.com"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "\n\n No spam to my email, please!");

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }
}