Generate JHipster 9.3.0 baseline application

src/main/java/com/example/questionbank/service/MailService.java

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+package com.example.questionbank.service;
+
+import com.example.questionbank.domain.User;
+import jakarta.mail.MessagingException;
+import jakarta.mail.internet.MimeMessage;
+import java.nio.charset.StandardCharsets;
+import java.util.Locale;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.context.MessageSource;
+import org.springframework.mail.MailException;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.mail.javamail.MimeMessageHelper;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.thymeleaf.context.Context;
+import org.thymeleaf.spring6.SpringTemplateEngine;
+import tech.jhipster.config.JHipsterProperties;
+
+/**
+ * Service for sending emails asynchronously.
+ * <p>
+ * We use the {@link Async} annotation to send emails asynchronously.
+ */
+@Service
+public class MailService {
+
+    private static final Logger LOG = LoggerFactory.getLogger(MailService.class);
+
+    private static final String USER = "user";
+
+    private static final String BASE_URL = "baseUrl";
+
+    private final JHipsterProperties jHipsterProperties;
+
+    private final JavaMailSender javaMailSender;
+
+    private final MessageSource messageSource;
+
+    private final SpringTemplateEngine templateEngine;
+
+    public MailService(
+        JHipsterProperties jHipsterProperties,
+        JavaMailSender javaMailSender,
+        MessageSource messageSource,
+        SpringTemplateEngine templateEngine
+    ) {
+        this.jHipsterProperties = jHipsterProperties;
+        this.javaMailSender = javaMailSender;
+        this.messageSource = messageSource;
+        this.templateEngine = templateEngine;
+    }
+
+    @Async
+    public void sendEmail(String to, String subject, String content, boolean isMultipart, boolean isHtml) {
+        sendEmailSync(to, subject, content, isMultipart, isHtml);
+    }
+
+    private void sendEmailSync(String to, String subject, String content, boolean isMultipart, boolean isHtml) {
+        LOG.debug(
+            "Send email[multipart '{}' and html '{}'] to '{}' with subject '{}' and content={}",
+            isMultipart,
+            isHtml,
+            to,
+            subject,
+            content
+        );
+
+        // Prepare message using a Spring helper
+        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
+        try {
+            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, isMultipart, StandardCharsets.UTF_8.name());
+            message.setTo(to);
+            message.setFrom(jHipsterProperties.getMail().getFrom());
+            message.setSubject(subject);
+            message.setText(content, isHtml);
+            javaMailSender.send(mimeMessage);
+            LOG.debug("Sent email to User '{}'", to);
+        } catch (MailException | MessagingException e) {
+            LOG.warn("Email could not be sent to user '{}'", to, e);
+        }
+    }
+
+    @Async
+    public void sendEmailFromTemplate(User user, String templateName, String titleKey) {
+        sendEmailFromTemplateSync(user, templateName, titleKey);
+    }
+
+    private void sendEmailFromTemplateSync(User user, String templateName, String titleKey) {
+        if (user.getEmail() == null) {
+            LOG.debug("Email doesn't exist for user '{}'", user.getLogin());
+            return;
+        }
+        Locale locale = Locale.forLanguageTag(user.getLangKey());
+        Context context = new Context(locale);
+        context.setVariable(USER, user);
+        context.setVariable(BASE_URL, jHipsterProperties.getMail().getBaseUrl());
+        String content = templateEngine.process(templateName, context);
+        String subject = messageSource.getMessage(titleKey, null, locale);
+        sendEmailSync(user.getEmail(), subject, content, false, true);
+    }
+
+    @Async
+    public void sendActivationEmail(User user) {
+        LOG.debug("Sending activation email to '{}'", user.getEmail());
+        sendEmailFromTemplateSync(user, "mail/activationEmail", "email.activation.title");
+    }
+
+    @Async
+    public void sendCreationEmail(User user) {
+        LOG.debug("Sending creation email to '{}'", user.getEmail());
+        sendEmailFromTemplateSync(user, "mail/creationEmail", "email.activation.title");
+    }
+
+    @Async
+    public void sendPasswordResetMail(User user) {
+        LOG.debug("Sending password reset email to '{}'", user.getEmail());
+        sendEmailFromTemplateSync(user, "mail/passwordResetEmail", "email.reset.title");
+    }
+}