[server] SMTP Mailing

16 files changed, 668 insertions, 127 deletions

diff --git a/dozentenmodulserver/setup/sat-01-schema.sql b/dozentenmodulserver/setup/sat-01-schema.sql
index dab97282..051ab485 100644
--- a/dozentenmodulserver/setup/sat-01-schema.sql
+++ b/dozentenmodulserver/setup/sat-01-schema.sql
@@ -196,6 +196,15 @@ CREATE TABLE IF NOT EXISTS `configuration` (
   PRIMARY KEY (`parameter`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
+CREATE TABLE IF NOT EXISTS `mailqueue` (
+  `mailid` char(36) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
+  `userid` char(36) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
+  `message` text NOT NULL,
+  `failcount` int(11) NOT NULL DEFAULT '0',
+  `dateline` bigint(20) NOT NULL,
+  PRIMARY KEY (`mailid`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
 ALTER TABLE `lectureuser`
   ADD CONSTRAINT `fk_lectureuser_1` FOREIGN KEY (`lectureid`) REFERENCES `sat`.`lecture` (`lectureid`) ON DELETE CASCADE ON UPDATE CASCADE;
 
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/App.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/App.java
index 86d231ef..bdbc8b7f 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/App.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/App.java
@@ -16,6 +16,7 @@ import org.openslx.bwlp.sat.database.Database;
 import org.openslx.bwlp.sat.database.mappers.DbImage;
 import org.openslx.bwlp.sat.fileserv.FileServer;
 import org.openslx.bwlp.sat.maintenance.DeleteOldImages;
+import org.openslx.bwlp.sat.maintenance.MailFlusher;
 import org.openslx.bwlp.sat.maintenance.SendExpireWarning;
 import org.openslx.bwlp.sat.thrift.BinaryListener;
 import org.openslx.bwlp.sat.thrift.cache.OperatingSystemList;
@@ -98,6 +99,7 @@ public class App {
 		// Set up maintenance tasks
 		DeleteOldImages.init();
 		SendExpireWarning.init();
+		MailFlusher.init();
 
 		// Start Thrift Server
 		Thread t;
@@ -132,6 +134,7 @@ public class App {
 			NetRule nn = Json.deserializeThrift(data, NetRule.class);
 			LOGGER.info(nn);
 		}
+
 		// Wait for servers
 		for (Thread wait : servers) {
 			boolean success = false;
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbConfiguration.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbConfiguration.java
index 27dc2b6e..8fb4497e 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbConfiguration.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbConfiguration.java
@@ -6,6 +6,7 @@ import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
 import java.security.KeyStore;
 import java.security.KeyStoreException;
 import java.security.NoSuchAlgorithmException;
@@ -18,6 +19,8 @@ import org.apache.log4j.Logger;
 import org.openslx.bwlp.sat.database.Database;
 import org.openslx.bwlp.sat.database.MysqlConnection;
 import org.openslx.bwlp.sat.database.MysqlStatement;
+import org.openslx.bwlp.sat.mail.MailQueue.MailConfig;
+import org.openslx.bwlp.sat.util.Json;
 
 public class DbConfiguration {
 
@@ -25,6 +28,8 @@ public class DbConfiguration {
 
 	private static final String KEY_CERTIFICATE = "certstore";
 
+	private static final String KEY_MAILCONFIG = "mailconfig";
+
 	public static KeyStore loadKeyStore(String password) throws KeyStoreException, SQLException,
 			NoSuchAlgorithmException, CertificateException, IOException {
 		KeyStore keystore = KeyStore.getInstance("JKS");
@@ -80,4 +85,17 @@ public class DbConfiguration {
 		}
 	}
 
+	/**
+	 * Returns mailing configuration (SMTP) from data base.
+	 * 
+	 * @return mailing configuration (SMTP) from data base.
+	 * @throws SQLException
+	 */
+	public static MailConfig getMailConfig() throws SQLException {
+		byte[] conf = retrieve(KEY_MAILCONFIG);
+		if (conf == null)
+			return null;
+		return Json.deserialize(new String(conf, StandardCharsets.UTF_8), MailConfig.class);
+	}
+
 }
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbImage.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbImage.java
index c03d8322..95d6380c 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbImage.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbImage.java
@@ -14,7 +14,7 @@ import org.openslx.bwlp.sat.database.MysqlConnection;
 import org.openslx.bwlp.sat.database.MysqlStatement;
 import org.openslx.bwlp.sat.database.Paginator;
 import org.openslx.bwlp.sat.database.models.LocalImageVersion;
-import org.openslx.bwlp.sat.maintenance.Mailer;
+import org.openslx.bwlp.sat.mail.MailGenerator;
 import org.openslx.bwlp.sat.permissions.User;
 import org.openslx.bwlp.sat.util.FileSystem;
 import org.openslx.bwlp.sat.util.Util;
@@ -701,7 +701,7 @@ public class DbImage {
 		}
 		// Now update the latestversionid of the baseimage if applicable
 		if (setLatestVersion(connection, imageBaseId, latestVersion)) {
-			Mailer.versionDeleted(imageBaseId, changingVersion, latestVersion);
+			MailGenerator.versionDeleted(imageBaseId, changingVersion, latestVersion);
 		}
 	}
 
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbLecture.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbLecture.java
index c9f1c6df..8492dd58 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbLecture.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbLecture.java
@@ -13,7 +13,7 @@ import org.openslx.bwlp.sat.database.Database;
 import org.openslx.bwlp.sat.database.MysqlConnection;
 import org.openslx.bwlp.sat.database.MysqlStatement;
 import org.openslx.bwlp.sat.database.models.LocalImageVersion;
-import org.openslx.bwlp.sat.maintenance.Mailer;
+import org.openslx.bwlp.sat.mail.MailGenerator;
 import org.openslx.bwlp.sat.permissions.User;
 import org.openslx.bwlp.sat.util.Json;
 import org.openslx.bwlp.sat.util.Util;
@@ -344,7 +344,7 @@ public class DbLecture {
 		stmt.setString("imagebaseid", imageBaseId);
 		stmt.executeUpdate();
 		// Send informative mail to lecture admins
-		Mailer.lectureAutoUpdate(lectures, newVersion);
+		MailGenerator.lectureAutoUpdate(lectures, newVersion);
 	}
 
 	/**
@@ -365,14 +365,14 @@ public class DbLecture {
 		if (newVersion == null) {
 			stmt = connection.prepareStatement("UPDATE lecture SET isenabled = 0 WHERE imageversionid = :oldversionid");
 			stmt.setString("oldversionid", oldVersion.imageVersionId);
-			Mailer.lectureDeactivated(lectures);
+			MailGenerator.lectureDeactivated(lectures);
 		} else {
 			// Update and send info mail
 			stmt = connection.prepareStatement("UPDATE lecture SET imageversionid = :newversionid"
 					+ " WHERE imageversionid = :oldversionid");
 			stmt.setString("oldversionid", oldVersion.imageVersionId);
 			stmt.setString("newversionid", newVersion.imageVersionId);
-			Mailer.lectureForcedUpdate(lectures, newVersion);
+			MailGenerator.lectureForcedUpdate(lectures, newVersion);
 		}
 		stmt.executeUpdate();
 	}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbMailQueue.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbMailQueue.java
new file mode 100644
index 00000000..67d3591a
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbMailQueue.java
@@ -0,0 +1,95 @@
+package org.openslx.bwlp.sat.database.mappers;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.log4j.Logger;
+import org.openslx.bwlp.sat.database.Database;
+import org.openslx.bwlp.sat.database.MysqlConnection;
+import org.openslx.bwlp.sat.database.MysqlStatement;
+import org.openslx.bwlp.sat.mail.Mail;
+
+public class DbMailQueue {
+
+	private static final Logger LOGGER = Logger.getLogger(DbMailQueue.class);
+
+	public static void queue(Mail mail) throws SQLException {
+		try (MysqlConnection connection = Database.getConnection()) {
+			MysqlStatement stmt = connection.prepareStatement("INSERT INTO mailqueue"
+					+ " (mailid, userid, message, failcount, dateline) VALUES"
+					+ " (:mailid, :userid, :message, 0, UNIX_TIMESTAMP())");
+			stmt.setString("mailid", mail.id);
+			stmt.setString("userid", mail.userId);
+			stmt.setString("message", mail.message);
+			stmt.executeUpdate();
+			connection.commit();
+		} catch (SQLException e) {
+			LOGGER.error("Query failed in DbMailQueue.queue()", e);
+			throw e;
+		}
+	}
+
+	public static List<Mail> getQueued(int batchSize) throws SQLException {
+		if (batchSize <= 0)
+			throw new IllegalArgumentException("batchSize must be > 0");
+		try (MysqlConnection connection = Database.getConnection()) {
+			// Delete old mails that got stuck in the queue, optimize table
+			MysqlStatement delStmt = connection.prepareStatement("DELETE FROM mailqueue"
+					+ " WHERE UNIX_TIMESTAMP() - dateline > 86400 * 2");
+			int cnt = delStmt.executeUpdate();
+			if (cnt != 0 || Math.random() < .01) {
+				MysqlStatement optStmt = connection.prepareStatement("OPTIMIZE TABLE mailqueue");
+				optStmt.executeUpdate();
+			}
+			MysqlStatement stmt = connection.prepareStatement("SELECT"
+					+ " mailid, userid, message FROM mailqueue"
+					+ " WHERE failcount < 2 ORDER BY dateline DESC LIMIT " + batchSize);
+			ResultSet rs = stmt.executeQuery();
+			List<Mail> list = new ArrayList<>();
+			while (rs.next()) {
+				list.add(new Mail(rs.getString("mailid"), rs.getString("userid"), rs.getString("message")));
+			}
+			connection.commit();
+			return list;
+		} catch (SQLException e) {
+			LOGGER.error("Query failed in DbMailQueue.getQueued()", e);
+			throw e;
+		}
+	}
+
+	public static void markFailed(List<Mail> mails) throws SQLException {
+		if (mails.isEmpty())
+			return;
+		try (MysqlConnection connection = Database.getConnection()) {
+			MysqlStatement stmt = connection.prepareStatement("UPDATE mailqueue"
+					+ " SET failcount = failcount + 1   WHERE mailid = :mailid");
+			for (Mail mail : mails) {
+				stmt.setString("mailid", mail.id);
+				stmt.executeUpdate();
+			}
+			connection.commit();
+		} catch (SQLException e) {
+			LOGGER.error("Query failed in DbMailQueue.markFailed()", e);
+			throw e;
+		}
+	}
+
+	public static void markSent(List<Mail> mails) throws SQLException {
+		if (mails.isEmpty())
+			return;
+		try (MysqlConnection connection = Database.getConnection()) {
+			MysqlStatement stmt = connection.prepareStatement("DELETE FROM mailqueue WHERE mailid = :mailid");
+			for (Mail mail : mails) {
+				stmt.setString("mailid", mail.id);
+				stmt.executeUpdate();
+			}
+			connection.commit();
+		} catch (SQLException e) {
+			LOGGER.error("Query failed in DbMailQueue.markFailed()", e);
+			throw e;
+		}
+	}
+
+}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbUser.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbUser.java
index c0e96296..303b8e15 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbUser.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/database/mappers/DbUser.java
@@ -20,34 +20,20 @@ import org.openslx.util.TimeoutHashMap;
 
 public class DbUser {
 
-	private static final Logger LOGGER = Logger.getLogger(DbUser.class);
-
-	private static Map<String, UserInfo> userCache;
+	public static class User {
+		public final UserInfo ui;
+		public final LocalUser local;
 
-	private static void initCache() throws SQLException {
-		if (userCache != null)
-			return;
-		synchronized (DbUser.class) {
-			if (userCache == null) {
-				try (MysqlConnection connection = Database.getConnection()) {
-					userCache = new TimeoutHashMap<>(TimeUnit.DAYS.toMillis(2));
-					MysqlStatement stmt = connection.prepareStatement("SELECT userid, firstname, lastname, email, organizationid"
-							+ " FROM user ORDER BY lastlogin DESC LIMIT 30");
-					ResultSet rs = stmt.executeQuery();
-					while (rs.next()) {
-						UserInfo user = new UserInfo(rs.getString("userid"), rs.getString("firstname"),
-								rs.getString("lastname"), rs.getString("email"),
-								rs.getString("organizationid"));
-						userCache.put(user.userId, user);
-					}
-				} catch (SQLException e) {
-					LOGGER.error("Query failed in DbUser.initCache()", e);
-					throw e;
-				}
-			}
+		public User(UserInfo ui, LocalUser local) {
+			this.ui = ui;
+			this.local = local;
 		}
 	}
 
+	private static final Logger LOGGER = Logger.getLogger(DbUser.class);
+
+	private static Map<String, User> userCache = new TimeoutHashMap<>(TimeUnit.MINUTES.toMillis(15));
+
 	/**
 	 * Get all users, starting at page <code>page</code>.
 	 * This function will return a maximum of {@link #PER_PAGE} results, so
@@ -61,7 +47,8 @@ public class DbUser {
 		if (page < 0)
 			return new ArrayList<>(1);
 		try (MysqlConnection connection = Database.getConnection()) {
-			MysqlStatement stmt = connection.prepareStatement("SELECT userid, firstname, lastname, email, organizationid"
+			MysqlStatement stmt = connection.prepareStatement("SELECT userid, firstname, lastname, email, organizationid,"
+					+ " lastlogin, canlogin, issuperuser, emailnotifications"
 					+ " FROM user ORDER BY userid ASC " + Paginator.limitStatement(page));
 			ResultSet rs = stmt.executeQuery();
 			List<UserInfo> list = new ArrayList<>();
@@ -150,30 +137,29 @@ public class DbUser {
 			LOGGER.error("Query failed in DbUser.writeUserOnLogin()", e);
 			throw e;
 		}
-		synchronized (DbUser.class) {
-			initCache();
-			userCache.put(ui.userId, ui);
-		}
 	}
 
-	public static UserInfo getCached(String userId) throws SQLException, TNotFoundException {
+	public static User getCached(String userId) throws SQLException, TNotFoundException {
 		synchronized (DbUser.class) {
-			initCache();
-			UserInfo user = userCache.get(userId);
+			User user = userCache.get(userId);
 			if (user != null)
 				return user;
 		}
 		try (MysqlConnection connection = Database.getConnection()) {
-			MysqlStatement stmt = connection.prepareStatement("SELECT userid, firstname, lastname, email, organizationid"
+			MysqlStatement stmt = connection.prepareStatement("SELECT userid, firstname, lastname, email, organizationid,"
+					+ " lastlogin, canlogin, issuperuser, emailnotifications"
 					+ " FROM user WHERE userid = :userid");
 			stmt.setString("userid", userId);
 			ResultSet rs = stmt.executeQuery();
 			if (!rs.next())
 				throw new TNotFoundException();
-			UserInfo user = new UserInfo(rs.getString("userid"), rs.getString("firstname"),
+			UserInfo userInfo = new UserInfo(rs.getString("userid"), rs.getString("firstname"),
 					rs.getString("lastname"), rs.getString("email"), rs.getString("organizationid"));
+			LocalUser local = new LocalUser(rs.getLong("lastlogin"), rs.getBoolean("canlogin"),
+					rs.getBoolean("issuperuser"), rs.getBoolean("emailnotifications"));
+			User user = new User(userInfo, local);
 			synchronized (DbUser.class) {
-				userCache.put(user.userId, user);
+				userCache.put(userInfo.userId, user);
 			}
 			return user;
 		} catch (SQLException e) {
@@ -181,5 +167,4 @@ public class DbUser {
 			throw e;
 		}
 	}
-
 }
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/Mail.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/Mail.java
new file mode 100644
index 00000000..a795a52e
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/Mail.java
@@ -0,0 +1,15 @@
+package org.openslx.bwlp.sat.mail;
+
+public class Mail {
+
+	public final String id;
+	public final String userId;
+	public final String message;
+
+	public Mail(String id, String userId, String message) {
+		this.id = id;
+		this.userId = userId;
+		this.message = message;
+	}
+
+}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/Mailer.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/MailGenerator.java
index 23482514..3a976b3d 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/Mailer.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/MailGenerator.java
@@ -1,4 +1,4 @@
-package org.openslx.bwlp.sat.maintenance;
+package org.openslx.bwlp.sat.mail;
 
 import java.sql.SQLException;
 import java.util.ArrayList;
@@ -8,12 +8,16 @@ import java.util.Map;
 import java.util.Map.Entry;
 
 import org.apache.log4j.Logger;
+import org.openslx.bwlp.sat.database.mappers.DbConfiguration;
 import org.openslx.bwlp.sat.database.mappers.DbImage;
 import org.openslx.bwlp.sat.database.mappers.DbImagePermissions;
 import org.openslx.bwlp.sat.database.mappers.DbLecturePermissions;
 import org.openslx.bwlp.sat.database.mappers.DbUser;
+import org.openslx.bwlp.sat.database.mappers.DbUser.User;
 import org.openslx.bwlp.sat.database.models.LocalImageVersion;
+import org.openslx.bwlp.sat.mail.MailQueue.MailConfig;
 import org.openslx.bwlp.sat.util.Formatter;
+import org.openslx.bwlp.sat.util.Util;
 import org.openslx.bwlp.thrift.iface.ImageDetailsRead;
 import org.openslx.bwlp.thrift.iface.ImagePermissions;
 import org.openslx.bwlp.thrift.iface.ImageVersionDetails;
@@ -22,11 +26,20 @@ import org.openslx.bwlp.thrift.iface.LectureSummary;
 import org.openslx.bwlp.thrift.iface.TNotFoundException;
 import org.openslx.bwlp.thrift.iface.UserInfo;
 
-public class Mailer {
+public class MailGenerator {
 
-	private static final Logger LOGGER = Logger.getLogger(Mailer.class);
+	private static final Logger LOGGER = Logger.getLogger(MailGenerator.class);
 
+	/**
+	 * Called when an image has been updated, and linked lectures will be moved
+	 * to the new image version.
+	 * 
+	 * @param lectures List of affected lectures
+	 * @param newVersion version id of new image
+	 */
 	public static void lectureAutoUpdate(List<LectureSummary> lectures, LocalImageVersion newVersion) {
+		if (!hasMailConfig())
+			return;
 		for (LectureSummary lecture : lectures) {
 			LOGGER.debug("Auto-Update mail for " + lecture.lectureId + " " + lecture.lectureName);
 			List<UserInfo> relevantUsers = getUserToMail(lecture);
@@ -37,6 +50,8 @@ public class Mailer {
 	}
 
 	public static void lectureForcedUpdate(List<LectureSummary> lectures, LocalImageVersion newVersion) {
+		if (!hasMailConfig())
+			return;
 		for (LectureSummary lecture : lectures) {
 			LOGGER.debug("Forced-Update mail for " + lecture.lectureId + " " + lecture.lectureName);
 			List<UserInfo> relevantUsers = getUserToMail(lecture);
@@ -47,6 +62,8 @@ public class Mailer {
 	}
 
 	public static void lectureDeactivated(List<LectureSummary> lectures) {
+		if (!hasMailConfig())
+			return;
 		for (LectureSummary lecture : lectures) {
 			LOGGER.debug("Deactivated mail for " + lecture.lectureId + " " + lecture.lectureName);
 			List<UserInfo> relevantUsers = getUserToMail(lecture);
@@ -56,62 +73,10 @@ public class Mailer {
 		}
 	}
 
-	private static List<UserInfo> getUserToMail(LectureSummary lecture) {
-		Map<String, LecturePermissions> users;
-		try {
-			users = DbLecturePermissions.getForLecture(lecture.lectureId, false);
-		} catch (SQLException e) {
-			users = new HashMap<>();
-		}
-		users.put(lecture.ownerId, new LecturePermissions(true, true));
-		List<UserInfo> list = new ArrayList<>(users.size());
-		for (Entry<String, LecturePermissions> entry : users.entrySet()) {
-			LecturePermissions perms = entry.getValue();
-			if (!perms.admin && !perms.edit)
-				continue;
-			UserInfo user;
-			try {
-				user = DbUser.getCached(entry.getKey());
-			} catch (TNotFoundException e) {
-				LOGGER.warn("UserID " + entry.getKey() + " unknown");
-				continue;
-			} catch (SQLException e) {
-				continue; // Logging happened in DbUser
-			}
-			list.add(user);
-		}
-		return list;
-	}
-
-	private static List<UserInfo> getUserToMail(ImageDetailsRead image) {
-		Map<String, ImagePermissions> users;
-		try {
-			users = DbImagePermissions.getForImageBase(image.imageBaseId, false);
-		} catch (SQLException e) {
-			users = new HashMap<>();
-		}
-		users.put(image.ownerId, new ImagePermissions(true, true, true, true));
-		List<UserInfo> list = new ArrayList<>(users.size());
-		for (Entry<String, ImagePermissions> entry : users.entrySet()) {
-			ImagePermissions perms = entry.getValue();
-			if (!perms.admin && !perms.edit)
-				continue;
-			UserInfo user;
-			try {
-				user = DbUser.getCached(entry.getKey());
-			} catch (TNotFoundException e) {
-				LOGGER.warn("UserID " + entry.getKey() + " unknown");
-				continue;
-			} catch (SQLException e) {
-				continue; // Logging happened in DbUser
-			}
-			list.add(user);
-		}
-		return list;
-	}
-
 	public static void versionDeleted(String imageBaseId, LocalImageVersion oldLocal,
 			LocalImageVersion newLocal) {
+		if (!hasMailConfig())
+			return;
 		ImageDetailsRead image;
 		try {
 			image = DbImage.getImageDetails(null, imageBaseId);
@@ -137,8 +102,9 @@ public class Mailer {
 		} else {
 			String uploaderName;
 			try {
-				UserInfo uploader = DbUser.getCached(newVersion.uploaderId);
-				uploaderName = uploader.firstName + " " + uploader.lastName + " <" + uploader.eMail + ">";
+				User uploader = DbUser.getCached(newVersion.uploaderId);
+				uploaderName = uploader.ui.firstName + " " + uploader.ui.lastName + " <" + uploader.ui.eMail
+						+ ">";
 			} catch (TNotFoundException | SQLException e) {
 				uploaderName = "an unknown person";
 				;
@@ -159,6 +125,8 @@ public class Mailer {
 	}
 
 	public static void sendDeletionReminder(LocalImageVersion version, int days) {
+		if (!hasMailConfig())
+			return;
 		ImageDetailsRead image;
 		try {
 			image = DbImage.getImageDetails(null, version.imageBaseId);
@@ -174,6 +142,8 @@ public class Mailer {
 	}
 
 	public static void sendDeletionRemainder(LectureSummary lecture, int days) {
+		if (!hasMailConfig())
+			return;
 		List<UserInfo> relevantUsers = getUserToMail(lecture);
 		for (UserInfo user : relevantUsers) {
 			LOGGER.debug("[lecture:" + lecture.lectureName + "] Sending warning mail to "
@@ -181,4 +151,77 @@ public class Mailer {
 		}
 	}
 
+	public static boolean isValidMailConfig(MailConfig conf) {
+		return conf != null && conf.port != 0 && !Util.isEmptyString(conf.host)
+				&& !Util.isEmptyString(conf.senderAddress);
+	}
+
+	private static boolean hasMailConfig() {
+		MailConfig conf;
+		try {
+			conf = DbConfiguration.getMailConfig();
+		} catch (SQLException e) {
+			return false;
+		}
+		return isValidMailConfig(conf);
+	}
+
+	private static List<UserInfo> getUserToMail(LectureSummary lecture) {
+		Map<String, LecturePermissions> users;
+		try {
+			users = DbLecturePermissions.getForLecture(lecture.lectureId, false);
+		} catch (SQLException e) {
+			users = new HashMap<>();
+		}
+		users.put(lecture.ownerId, new LecturePermissions(true, true));
+		List<UserInfo> list = new ArrayList<>(users.size());
+		for (Entry<String, LecturePermissions> entry : users.entrySet()) {
+			LecturePermissions perms = entry.getValue();
+			if (!perms.admin && !perms.edit)
+				continue;
+			User user;
+			try {
+				user = DbUser.getCached(entry.getKey());
+			} catch (TNotFoundException e) {
+				LOGGER.warn("UserID " + entry.getKey() + " unknown");
+				continue;
+			} catch (SQLException e) {
+				continue; // Logging happened in DbUser
+			}
+			if (user.local.emailNotifications) {
+				list.add(user.ui);
+			}
+		}
+		return list;
+	}
+
+	private static List<UserInfo> getUserToMail(ImageDetailsRead image) {
+		Map<String, ImagePermissions> users;
+		try {
+			users = DbImagePermissions.getForImageBase(image.imageBaseId, false);
+		} catch (SQLException e) {
+			users = new HashMap<>();
+		}
+		users.put(image.ownerId, new ImagePermissions(true, true, true, true));
+		List<UserInfo> list = new ArrayList<>(users.size());
+		for (Entry<String, ImagePermissions> entry : users.entrySet()) {
+			ImagePermissions perms = entry.getValue();
+			if (!perms.admin && !perms.edit)
+				continue;
+			User user;
+			try {
+				user = DbUser.getCached(entry.getKey());
+			} catch (TNotFoundException e) {
+				LOGGER.warn("UserID " + entry.getKey() + " unknown");
+				continue;
+			} catch (SQLException e) {
+				continue; // Logging happened in DbUser
+			}
+			if (user.local.emailNotifications) {
+				list.add(user.ui);
+			}
+		}
+		return list;
+	}
+
 }
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/MailQueue.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/MailQueue.java
new file mode 100644
index 00000000..ae1932e1
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/MailQueue.java
@@ -0,0 +1,206 @@
+package org.openslx.bwlp.sat.mail;
+
+import java.io.IOException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+import javax.security.auth.login.LoginException;
+
+import org.apache.log4j.Logger;
+import org.openslx.bwlp.sat.database.mappers.DbConfiguration;
+import org.openslx.bwlp.sat.database.mappers.DbMailQueue;
+import org.openslx.bwlp.sat.database.mappers.DbUser;
+import org.openslx.bwlp.sat.database.mappers.DbUser.User;
+import org.openslx.bwlp.sat.mail.SmtpMailer.EncryptionMode;
+import org.openslx.bwlp.sat.maintenance.MailFlusher;
+import org.openslx.bwlp.sat.util.Util;
+import org.openslx.bwlp.thrift.iface.TNotFoundException;
+import org.openslx.bwlp.thrift.iface.UserInfo;
+import org.openslx.util.QuickTimer;
+import org.openslx.util.QuickTimer.Task;
+
+public class MailQueue {
+
+	public static class MailConfig {
+		public String host;
+		public int port;
+		public EncryptionMode ssl;
+		public String senderAddress;
+		public String replyTo;
+		public String password;
+		public String username;
+		public String serverName;
+	}
+
+	private static final Logger LOGGER = Logger.getLogger(MailQueue.class);
+
+	private static final int BATCH_SIZE = 25;
+
+	private static boolean busy = false;
+
+	/**
+	 * Convenience wrapper for {@link DbMailQueue#queue(Mail)}, swallowing any
+	 * {@link SQLException}, so the mailing will keep going (or try to at least)
+	 * 
+	 * @param mail Mail to queue for sending
+	 */
+	public static void queue(Mail mail) {
+		try {
+			DbMailQueue.queue(mail);
+		} catch (SQLException e) {
+		}
+	}
+
+	/**
+	 * Send queued messages. This operation is rate-limited. In case there might
+	 * be more messages to send, this function will return after sending some of
+	 * them, and schedule a maintenance job that will trigger this method again.
+	 * 
+	 * @throws InterruptedException
+	 */
+	public static void flush() throws InterruptedException {
+		synchronized (MailQueue.class) {
+			if (busy) // Will run again when the scheduler decides to
+				return;
+			busy = true;
+		}
+		try {
+			List<Mail> queuedMails;
+			try {
+				queuedMails = DbMailQueue.getQueued(BATCH_SIZE);
+			} catch (SQLException e) {
+				LOGGER.error("Cannot retrieve queued mails from DB");
+				return;
+			}
+			// Anything to do?
+			if (queuedMails.isEmpty())
+				return;
+			// Fetch SMTP config
+			MailConfig conf;
+			try {
+				conf = DbConfiguration.getMailConfig();
+			} catch (SQLException e) {
+				conf = null;
+				return;
+			}
+			if (!MailGenerator.isValidMailConfig(conf)) {
+				LOGGER.error("Cannot send mail with no mail config");
+				return;
+			}
+			// Setup mailer
+			SmtpMailer smtpc;
+			try {
+				smtpc = new SmtpMailer(conf.host, conf.port, conf.ssl, conf.senderAddress, conf.serverName,
+						conf.replyTo, conf.username, conf.password);
+			} catch (InvalidKeyException | LoginException | NoSuchAlgorithmException
+					| InvalidKeySpecException | IOException e) {
+				LOGGER.error("Could not initialize connection to SMTP server. Mails will not be sent", e);
+				return;
+			}
+			// Iterate over mail: Group by receiving user
+			Map<String, List<Mail>> batch = new HashMap<>();
+			for (Mail mail : queuedMails) {
+				List<Mail> list = batch.get(mail.userId);
+				if (list == null) {
+					list = new ArrayList<>();
+					batch.put(mail.userId, list);
+				}
+				list.add(mail);
+			}
+			// Send all the mails
+			int delaySeconds = 2;
+			boolean sendOk = true;
+			for (List<Mail> userBatch : batch.values()) {
+				if (userBatch.isEmpty()) {
+					continue; // Now how the hell did that happen?
+				}
+				User cachedUser;
+				try {
+					cachedUser = DbUser.getCached(userBatch.get(0).userId);
+				} catch (TNotFoundException | SQLException e) {
+					LOGGER.warn("Cannot get user for id " + userBatch.get(0).userId
+							+ ": Sending mails failed.");
+					try {
+						DbMailQueue.markFailed(userBatch);
+					} catch (SQLException e1) {
+					}
+					continue;
+				}
+				// Double-check if user wants mail (unlikely, but user might just have changed the setting)
+				if (!cachedUser.local.emailNotifications) {
+					try {
+						DbMailQueue.markSent(userBatch);
+					} catch (SQLException e) {
+					}
+					continue;
+				}
+				StringBuilder sb = new StringBuilder();
+				for (Mail mail : userBatch) {
+					if (sb.length() != 0) {
+						sb.append('\n');
+					}
+					sb.append("* ");
+					sb.append(mail.message);
+				}
+				sendOk = sendMail(conf, smtpc, cachedUser.ui, sb.toString());
+				LOGGER.debug("Sending mail to " + cachedUser.ui.eMail + ": "
+						+ (sendOk ? "success" : "failure"));
+				try {
+					if (sendOk) {
+						DbMailQueue.markSent(userBatch);
+					} else {
+						DbMailQueue.markFailed(userBatch);
+					}
+				} catch (SQLException e) {
+				}
+				Thread.sleep(delaySeconds * 1000);
+				delaySeconds += 1;
+			}
+			smtpc.close();
+			// We got a full batch from DB, call flush() again in a minute
+			if (queuedMails.size() == BATCH_SIZE && sendOk) {
+				callAgainInOneMinute();
+			}
+		} finally {
+			synchronized (MailQueue.class) {
+				busy = false;
+			}
+		}
+	}
+
+	private static void callAgainInOneMinute() {
+		QuickTimer.scheduleOnce(new Task() {
+			@Override
+			public void fire() {
+				MailFlusher.start();
+			}
+		}, TimeUnit.MINUTES.toMillis(1));
+	}
+
+	private static boolean sendMail(MailConfig conf, SmtpMailer smtpc, UserInfo user, String message) {
+		// TODO: Template
+		String fullMessage = "Guten Tag " + user.firstName + " " + user.lastName + ",\n\n"
+				+ "Bitte beachten Sie folgende Hinweise zu Virtuellen Maschinen und Veranstaltungen,\n"
+				+ "für die Sie als zuständige Person hinterlegt sind:\n\n";
+		fullMessage += message;
+		fullMessage += "\n\n"
+				+ "Dies ist eine automatisch generierte Mail. Wenn Sie keine Hinweise dieser Art\n"
+				+ "wünschen, melden Sie sich bitte mittels des Desktop-Clients an diesem\n"
+				+ "bwLehrpool Satellitenserver an, und deaktivieren Sie in den Einstellungen\n"
+				+ "e-Mail-Benachrichtigungen.";
+		if (!Util.isEmptyString(conf.replyTo)) {
+			fullMessage += "\n\nBei weiteren Fragen wenden Sie sich bitte an den Support unter\n"
+					+ conf.replyTo;
+		}
+		fullMessage += "\n\n-----------------------------\n" + "Generiert von " + conf.serverName;
+		return smtpc.send(user.eMail, "[bwLehrstuhl] Hinweise zu Ihren VMs/Veranstaltungen", fullMessage);
+	}
+
+}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/QuotingSmtpHeader.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/QuotingSmtpHeader.java
new file mode 100644
index 00000000..35be803a
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/QuotingSmtpHeader.java
@@ -0,0 +1,56 @@
+package org.openslx.bwlp.sat.mail;
+
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.StandardCharsets;
+
+import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.net.smtp.SimpleSMTPHeader;
+
+public class QuotingSmtpHeader extends SimpleSMTPHeader {
+
+	private static CharsetEncoder asciiEncoder = StandardCharsets.US_ASCII.newEncoder();
+
+	public QuotingSmtpHeader(String fromAddress, String fromDisplayName, String to, String subject) {
+		super(buildNamedAddress(fromAddress, fromDisplayName), to, wrapEncoding(subject));
+	}
+
+	public QuotingSmtpHeader(String from, String to, String subject) {
+		super(from, to, wrapEncoding(subject));
+	}
+
+	@Override
+	public void addHeaderField(String headerField, String value) {
+		super.addHeaderField(headerField, wrapEncoding(value));
+	}
+
+	@Override
+	public void addCC(String address) {
+		super.addCC(wrapEncoding(address));
+	}
+
+	private static String wrapEncoding(String input) {
+		return wrapEncoding(input, false);
+	}
+
+	private static String wrapEncoding(String input, boolean addQuotesIfSpaces) {
+		boolean isAscii;
+		synchronized (asciiEncoder) { // Has class-wide state vars
+			isAscii = asciiEncoder.canEncode(input);
+		}
+		if (isAscii) {
+			if (addQuotesIfSpaces && (input.contains(" ") || input.contains("\t")))
+				return "\"" + input + "\"";
+			return input;
+		}
+		return "=?utf-8?B?"
+				+ new String(Base64.encodeBase64(input.getBytes(StandardCharsets.UTF_8), false),
+						StandardCharsets.UTF_8) + "?=";
+	}
+
+	private static String buildNamedAddress(String address, String name) {
+		if (name == null)
+			return address;
+		return wrapEncoding(name, true) + " <" + address + ">";
+	}
+
+}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SmtpMailer.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/SmtpMailer.java
index 52c6d9b6..4f1b415e 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SmtpMailer.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/mail/SmtpMailer.java
@@ -1,4 +1,4 @@
-package org.openslx.bwlp.sat.maintenance;
+package org.openslx.bwlp.sat.mail;
 
 import java.io.IOException;
 import java.io.Writer;
@@ -11,14 +11,20 @@ import java.security.spec.InvalidKeySpecException;
 
 import javax.security.auth.login.LoginException;
 
+import org.apache.commons.net.PrintCommandListener;
+import org.apache.commons.net.ProtocolCommandEvent;
+import org.apache.commons.net.ProtocolCommandListener;
 import org.apache.commons.net.smtp.AuthenticatingSMTPClient;
 import org.apache.commons.net.smtp.AuthenticatingSMTPClient.AUTH_METHOD;
 import org.apache.commons.net.smtp.SMTPReply;
 import org.apache.commons.net.smtp.SimpleSMTPHeader;
+import org.apache.log4j.Logger;
+import org.openslx.bwlp.sat.util.Util;
 
 public class SmtpMailer {
 
 	// TODO Logging
+	private static final Logger LOGGER = Logger.getLogger(SmtpMailer.class);
 
 	public enum EncryptionMode {
 		NONE,
@@ -26,16 +32,19 @@ public class SmtpMailer {
 		EXPLICIT
 	}
 
-	private final String from;
+	private final String fromAddress;
+	private final String fromName;
 	private final String replyTo;
 	private final AuthenticatingSMTPClient client;
 
-	public SmtpMailer(String host, int port, EncryptionMode ssl, String from, String replyTo,
-			String username, String password) throws UnknownHostException, SocketException, IOException,
-			LoginException, InvalidKeyException, NoSuchAlgorithmException, InvalidKeySpecException {
+	public SmtpMailer(String host, int port, EncryptionMode ssl, String fromAddress, String fromName,
+			String replyTo, String username, String password) throws UnknownHostException, SocketException,
+			IOException, LoginException, InvalidKeyException, NoSuchAlgorithmException,
+			InvalidKeySpecException {
 		InetAddress[] ips = InetAddress.getAllByName(host);
 		if (ips == null || ips.length == 0)
 			throw new UnknownHostException(host);
+		LOGGER.debug("Mailing via " + host + ", " + ssl);
 		if (ssl == EncryptionMode.EXPLICIT || ssl == EncryptionMode.NONE) {
 			client = new AuthenticatingSMTPClient("TLSv1.2", false, "UTF-8");
 		} else {
@@ -43,6 +52,20 @@ public class SmtpMailer {
 		}
 		boolean cleanup = true;
 		try {
+			new ProtocolCommandListener() {
+
+				@Override
+				public void protocolReplyReceived(ProtocolCommandEvent event) {
+					event.getMessage();
+				}
+
+				@Override
+				public void protocolCommandSent(ProtocolCommandEvent event) {
+					// TODO Auto-generated method stub
+
+				}
+			};
+			client.addProtocolCommandListener(new PrintCommandListener(System.out));
 			client.setConnectTimeout(5000);
 			IOException conEx = null;
 			for (InetAddress ip : ips) {
@@ -66,17 +89,20 @@ public class SmtpMailer {
 			if (ssl == EncryptionMode.EXPLICIT && !client.execTLS()) {
 				throw new LoginException("STARTTLS (explicit TLS) failed");
 			}
-			boolean authed = false;
-			try {
-				authed = client.auth(AUTH_METHOD.CRAM_MD5, username, password);
-			} catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException e) {
-				e.printStackTrace();
-			}
-			if (!authed && !client.auth(AUTH_METHOD.PLAIN, username, password)) {
-				throw new LoginException("Server rejected AUTH command. Invalid username or password?");
+			if (!Util.isEmptyString(username)) {
+				boolean authed = false;
+				try {
+					authed = client.auth(AUTH_METHOD.CRAM_MD5, username, password);
+				} catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException e) {
+					e.printStackTrace();
+				}
+				if (!authed && !client.auth(AUTH_METHOD.PLAIN, username, password)) {
+					throw new LoginException("Server rejected AUTH command. Invalid username or password?");
+				}
 			}
 			cleanup = false;
-			this.from = from;
+			this.fromAddress = fromAddress;
+			this.fromName = fromName;
 			this.replyTo = replyTo;
 		} finally {
 			if (cleanup)
@@ -105,12 +131,14 @@ public class SmtpMailer {
 		SimpleSMTPHeader header;
 
 		try {
-			header = new SimpleSMTPHeader(from, recipient, subject);
-			if (replyTo != null && !replyTo.isEmpty()) {
+			header = new QuotingSmtpHeader(fromAddress, fromName, recipient, subject);
+			if (!Util.isEmptyString(replyTo)) {
 				header.addHeaderField("Reply-To", replyTo);
 			}
+			header.addHeaderField("Content-Type", "text/plain; charset=utf-8");
+			header.addHeaderField("Content-Transfer-Encoding", "8bit");
 
-			if (!client.setSender(from)) {
+			if (!client.setSender(fromAddress)) {
 				abort();
 				return false;
 			}
@@ -147,4 +175,17 @@ public class SmtpMailer {
 		}
 	}
 
+	public void close() {
+		if (client.isConnected()) {
+			try {
+				client.logout();
+			} catch (Exception e) { // Don't care
+			}
+			try {
+				client.disconnect();
+			} catch (Exception e) { // Don't care
+			}
+		}
+	}
+
 }
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/MailFlusher.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/MailFlusher.java
new file mode 100644
index 00000000..ca4003b4
--- /dev/null
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/MailFlusher.java
@@ -0,0 +1,58 @@
+package org.openslx.bwlp.sat.maintenance;
+
+import java.util.concurrent.TimeUnit;
+
+import org.apache.log4j.Logger;
+import org.joda.time.DateTime;
+import org.openslx.bwlp.sat.mail.MailQueue;
+import org.openslx.util.QuickTimer;
+import org.openslx.util.QuickTimer.Task;
+
+public class MailFlusher implements Runnable {
+
+	private static final Logger LOGGER = Logger.getLogger(MailFlusher.class);
+
+	private static final MailFlusher instance = new MailFlusher();
+
+	private static long blockedUntil = 0;
+
+	/**
+	 * Initialize the task. This schedules a timer that runs
+	 * every 5 minutes. If the hour of day reaches 3, it will fire
+	 * the task, and block it from running for the next 12 hours.
+	 */
+	public synchronized static void init() {
+		if (blockedUntil != 0)
+			return;
+		blockedUntil = 1;
+		QuickTimer.scheduleAtFixedRate(new Task() {
+			@Override
+			public void fire() {
+				if (blockedUntil > System.currentTimeMillis())
+					return;
+				DateTime now = DateTime.now();
+				if (now.getHourOfDay() != 3 || now.getMinuteOfHour() > 15)
+					return;
+				start();
+			}
+		}, TimeUnit.MINUTES.toMillis(6), TimeUnit.MINUTES.toMillis(10));
+	}
+
+	public synchronized static void start() {
+		if (blockedUntil > System.currentTimeMillis())
+			return;
+		if (Maintenance.trySubmit(instance)) {
+			blockedUntil = System.currentTimeMillis() + TimeUnit.MINUTES.toMillis(1);
+		}
+	}
+
+	@Override
+	public void run() {
+		try {
+			MailQueue.flush();
+		} catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+		}
+	}
+
+}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SendExpireWarning.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SendExpireWarning.java
index 96436471..187b7628 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SendExpireWarning.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/maintenance/SendExpireWarning.java
@@ -9,6 +9,7 @@ import org.joda.time.DateTime;
 import org.openslx.bwlp.sat.database.mappers.DbImage;
 import org.openslx.bwlp.sat.database.mappers.DbLecture;
 import org.openslx.bwlp.sat.database.models.LocalImageVersion;
+import org.openslx.bwlp.sat.mail.MailGenerator;
 import org.openslx.bwlp.sat.util.FileSystem;
 import org.openslx.bwlp.sat.util.Util;
 import org.openslx.bwlp.thrift.iface.LectureSummary;
@@ -73,7 +74,7 @@ public class SendExpireWarning implements Runnable {
 			final int days = (int) ((lecture.endTime - now) / 86400);
 			LOGGER.debug(lecture.lectureName + " expires in " + days);
 			if ((lecture.isEnabled && (days == 14 || days == 1)) || (days == 7)) {
-				Mailer.sendDeletionRemainder(lecture, days);
+				MailGenerator.sendDeletionRemainder(lecture, days);
 			}
 		}
 	}
@@ -99,7 +100,7 @@ public class SendExpireWarning implements Runnable {
 			LOGGER.debug(version.imageVersionId + " expires in " + days);
 			if ((version.isValid && (days == 14 || days == 7 || days == 1))
 					|| (!version.isValid && days == 3)) {
-				Mailer.sendDeletionReminder(version, days);
+				MailGenerator.sendDeletionReminder(version, days);
 			}
 		}
 	}
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Json.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Json.java
index bb222792..679cb6bf 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Json.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Json.java
@@ -16,6 +16,7 @@ import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParseException;
+import com.google.gson.JsonSyntaxException;
 
 public class Json {
 
@@ -43,11 +44,21 @@ public class Json {
 	 * @return instanceof T
 	 */
 	public static <T> T deserialize(String data, Class<T> classOfData) {
-		return gson.fromJson(data, classOfData);
+		try {
+			return gson.fromJson(data, classOfData);
+		} catch (JsonSyntaxException e) {
+			LOGGER.warn("Cannot deserialize to " + classOfData.getSimpleName(), e);
+			return null;
+		}
 	}
 
 	public static <T> T deserializeThrift(String data, Class<T> thriftClass) {
-		return gsonThriftBuilder.create().fromJson(data, thriftClass);
+		try {
+			return gsonThriftBuilder.create().fromJson(data, thriftClass);
+		} catch (JsonSyntaxException e) {
+			LOGGER.warn("Cannot deserialize to " + thriftClass.getSimpleName(), e);
+			return null;
+		}
 	}
 
 	/**
diff --git a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Util.java b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Util.java
index e2135e64..53bfa403 100644
--- a/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Util.java
+++ b/dozentenmodulserver/src/main/java/org/openslx/bwlp/sat/util/Util.java
@@ -43,8 +43,8 @@ public class Util {
 		}
 	}
 
-	private static Pattern stringChecker = Pattern.compile("[\\p{C}\\p{Zl}\\p{Zp}]");
-	private static Pattern nonSpaceMatcher = Pattern.compile("[^\\p{C}\\p{Z}]");
+	private static Pattern nonprintableExp = Pattern.compile("[\\p{C}\\p{Zl}\\p{Zp}]");
+	private static Pattern nonSpaceExp = Pattern.compile("[^\\p{C}\\p{Z}]");
 
 	/**
 	 * Whether the given string contains only printable characters.
@@ -53,13 +53,13 @@ public class Util {
 	 * @return
 	 */
 	public static boolean isPrintable(String string) {
-		return !stringChecker.matcher(string).find();
+		return !nonprintableExp.matcher(string).find();
 	}
 
 	public static boolean isEmptyString(String string) {
-		return !nonSpaceMatcher.matcher(string).find();
+		return string == null || !nonSpaceExp.matcher(string).find();
 	}
-	
+
 	public static long unixTime() {
 		return System.currentTimeMillis() / 1000;
 	}