reduce state in application

* by fetching and using mail-related data on-demand

src/main/java/de/rwth/idsg/steve/service/MailService.java

@@ -26,7 +26,6 @@
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
-import jakarta.annotation.PostConstruct;
 import jakarta.mail.Authenticator;
 import jakarta.mail.Message;
 import jakarta.mail.MessagingException;
@@ -35,11 +34,9 @@
 import jakarta.mail.Transport;
 import jakarta.mail.internet.InternetAddress;
 import jakarta.mail.internet.MimeMessage;
+
 import java.util.Properties;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReadWriteLock;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 /**
  * @author Sevket Goekay <[email protected]>
@@ -52,31 +49,8 @@ public class MailService {
     @Autowired private SettingsRepository settingsRepository;
     @Autowired private ScheduledExecutorService executorService;
 
-    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
-    private final Lock readLock = readWriteLock.readLock();
-    private final Lock writeLock = readWriteLock.writeLock();
-
-    private MailSettings settings;
-    private Session session;
-
-    @PostConstruct
-    public void loadSettingsFromDB() {
-        writeLock.lock();
-        try {
-            settings = settingsRepository.getMailSettings();
-        } finally {
-            writeLock.unlock();
-        }
-        session = createSession(getSettings());
-    }
-
     public MailSettings getSettings() {
-        readLock.lock();
-        try {
-            return this.settings;
-        } finally {
-            readLock.unlock();
-        }
+        return settingsRepository.getMailSettings();
     }
 
     public void sendTestMail() {
@@ -99,6 +73,7 @@ public void sendAsync(String subject, String body) {
 
     public void send(String subject, String body) throws MessagingException {
         MailSettings settings = getSettings();
+        Session session = createSession(getSettings());
 
         Message mail = new MimeMessage(session);
         mail.setSubject("[SteVe] " + subject);

src/main/java/de/rwth/idsg/steve/web/controller/AboutSettingsController.java

@@ -94,7 +94,6 @@ public String postSettings(@Valid @ModelAttribute("settingsForm") SettingsForm s
         }
 
         settingsRepository.update(settingsForm);
-        mailService.loadSettingsFromDB();
         return "redirect:/manager/settings";
     }
 
@@ -107,7 +106,6 @@ public String testMail(@Valid @ModelAttribute("settingsForm") SettingsForm setti
         }
 
         settingsRepository.update(settingsForm);
-        mailService.loadSettingsFromDB();
         mailService.sendTestMail();
 
         return "redirect:/manager/settings";