Learn-Monitor · Schlaumeier5 · Jun 6, 2026 · May 13, 2026 · May 13, 2026 · May 14, 2026
diff --git a/.gitignore b/.gitignore
@@ -8,4 +8,5 @@ bin
 .gradle
 build
 /modules
-/plugins
+/plugins
+logs
diff --git a/build.gradle.kts b/build.gradle.kts
@@ -7,7 +7,7 @@ plugins {
 
 group = "igs-landstuhl"
 
-version = "v2.0.0-SNAPSHOT-0"
+version = "v2.0.0-SNAPSHOT-1"
 
 application {
     mainClass.set("de.igslandstuhl.database.Application")
@@ -25,6 +25,10 @@ dependencies {
     implementation("org.jline:jline:3.30.6") // for better console input handling
     implementation("org.yaml:snakeyaml:2.2") // plugin imports
 
+    // Logging
+    implementation("org.slf4j:slf4j-api:2.0.13")
+    implementation("ch.qos.logback:logback-classic:1.5.6")
+
     testImplementation("org.junit.jupiter:junit-jupiter:5.13.4") // using JUnit 5 (latest)
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }

diff --git a/src/main/java/de/igslandstuhl/database/Application.java b/src/main/java/de/igslandstuhl/database/Application.java
@@ -5,6 +5,8 @@
 import java.util.List;
 
 import org.jline.reader.UserInterruptException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import de.igslandstuhl.database.api.SerializationException;
 import de.igslandstuhl.database.api.Subject;
@@ -30,6 +32,10 @@ public final class Application {
     public static final String TITLE_DELIMITER = "¶";
     public static final String TASK_TITLE_DELIMITER = "\\|";
     public static final String TASK_DELIMITER = "¤";
+
+    public static final Logger LOGGER = LoggerFactory.getLogger(Application.class);
+    public static final Logger LOGGER_API = LoggerFactory.getLogger("de.igslandstuhl.database.api");
+
     private static Application instance = new Application(new String[] {"--test-environment", "true"});
     public static Application getInstance() {
         return instance;
@@ -89,7 +95,6 @@ public Topic[] readFile(String file) throws SerializationException, SQLException
                 }
             }
         } catch (Throwable t) {
-            t.printStackTrace();
             throw new SerializationException("Failed to read file", t);
         }
 
@@ -98,15 +103,20 @@ public Topic[] readFile(String file) throws SerializationException, SQLException
     }
 
     public static void main(String[] args) throws Exception {
+        LOGGER.info("Starting up student-database...");
+
         instance = new Application(args);
 
         PluginLoader.getInstance().preloadPlugins();
 
         if (!getInstance().suppressCmd()) {
+            LOGGER.info("Setting up command line...");
             Command.registerCommands();
             CommandLineUtils.setup();
         }
-
+
+        LOGGER.info("Setting up server...");
+
         Server.getInstance().getConnection().createTables();
 
         Holiday.setupCurrentSchoolYear();
@@ -119,14 +129,17 @@ public static void main(String[] args) throws Exception {
         GetRequestHandler.getInstance().registerHandlers();
 
         if (getInstance().runsWebServer()) {
+            LOGGER.info("Starting WebServer...");
             Server.getInstance().getWebServer().start();
         }
 
         PluginLoader.getInstance().enablePlugins();
 
+        LOGGER.info("Adding shutdown hook for plugin cleanup...");
         Runtime.getRuntime().addShutdownHook(new Thread(() -> PluginLoader.getInstance().unloadPlugins(),"Plugin cleanup thread"));
 
         try {
+            LOGGER.info("Starting main loop...");
             while (true) {
                 if (!getInstance().suppressCmd()) {
                     CommandLineUtils.waitForCommandAndExec();

diff --git a/src/main/java/de/igslandstuhl/database/api/Admin.java b/src/main/java/de/igslandstuhl/database/api/Admin.java
@@ -2,6 +2,7 @@
 
 import java.sql.SQLException;
 
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
 
@@ -61,7 +62,7 @@ public static Admin get(String username) {
         try {
             return Server.getInstance().processSingleRequest(Admin::fromSQL, "get_admin_by_username", SQL_FIELDS, username);
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve Admin user '{}' from database", username, e);
             return null;
         }
     }

diff --git a/src/main/java/de/igslandstuhl/database/api/SchoolClass.java b/src/main/java/de/igslandstuhl/database/api/SchoolClass.java
@@ -8,6 +8,7 @@
 import java.util.Objects;
 import java.util.stream.Collectors;
 
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
 
@@ -157,7 +158,7 @@ public List<Student> getStudents() {
                 "get_students_by_class", new String[] {"id"}, String.valueOf(id)
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve student list from database", e);
         }
         return studentIds.stream().map(Student::get).toList();
     }
@@ -168,7 +169,6 @@ public void delete() throws SQLException {
             try {
                 s.delete();
             } catch (SQLException e) {
-                e.printStackTrace();
                 throw new IllegalStateException(e);
             }
         });
@@ -214,7 +214,7 @@ public static SchoolClass get(int id) {
         try {
             return Server.getInstance().processSingleRequest(SchoolClass::fromSQL, "get_class_by_id", SQL_FIELDS, String.valueOf(id));
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SchoolClass with id {} from database", id, e);
             return null;
         }
     }
@@ -229,7 +229,7 @@ public static SchoolClass get(String label) {
         try {
             return Server.getInstance().processSingleRequest(SchoolClass::fromSQL, "get_class_by_label", SQL_FIELDS, label);
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SchoolClass with label '{}' from database", label, e);
             return null;
         }
     }
@@ -254,7 +254,7 @@ public static SchoolClass getOrCreate(String label) {
             try {
                 schoolClass = addClass(label, grade);
             } catch (SQLException e) {
-                e.printStackTrace();
+                Application.LOGGER_API.error("Failed to create previously not existing class with label {} and grade {}", label, grade, e);
             }
         }
         return schoolClass;
@@ -268,7 +268,7 @@ public static List<SchoolClass> getAll() {
                 "get_all_classes", new String[] {"id"}
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve a list of all classes from the database", e);
         }
         return ids.stream()
             .map(SchoolClass::get)

diff --git a/src/main/java/de/igslandstuhl/database/api/SchoolYear.java b/src/main/java/de/igslandstuhl/database/api/SchoolYear.java
@@ -2,6 +2,8 @@
 
 import java.sql.SQLException;
 import java.util.*;
+
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
 
@@ -124,7 +126,7 @@ public static SchoolYear get(int id) {
             if (year != null) years.put(id, year);
             return year;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SchoolYear with id {} from database", id, e);
             return null;
         }
     }
@@ -134,7 +136,7 @@ public static SchoolYear get(String label) {
                 return get(Integer.parseInt(fields[0]));
             }, "get_school_year_by_label", new String[] {"id"}, label);
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SchoolYear with label '{}' from database", label, e);
             return null;
         }
     }
@@ -156,7 +158,7 @@ public static List<SchoolYear> getAll() {
                 "get_all_school_years", SQL_FIELDS
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve a list of all school years from the database", e);
         }
         return all;
     }
@@ -176,7 +178,7 @@ public static SchoolYear getCurrentYear() {
             if (year != null) years.put(year.getId(), year);
             return year;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to load current school year from database", e);
             return null;
         }
     }

diff --git a/src/main/java/de/igslandstuhl/database/api/SpecialTask.java b/src/main/java/de/igslandstuhl/database/api/SpecialTask.java
@@ -7,6 +7,7 @@
 import java.util.List;
 import java.util.Map;
 
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
 
@@ -89,7 +90,7 @@ public static SpecialTask get(int id) {
             specialTasks.put(id, task);
             return task;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SpecialTask with id {} from database", id, e);
             return null;
         }
     }
@@ -114,7 +115,7 @@ public static List<SpecialTask> getSpecialTasksByName(String name) {
         try {
             Server.getInstance().processRequest(SpecialTask::addToCache, "get_special_tasks_by_name", SQL_FIELDS, name);
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get SpecialTask with name {} from database", name, e);
             return new ArrayList<>();
         }
         return specialTasks.values().stream()

diff --git a/src/main/java/de/igslandstuhl/database/api/Student.java b/src/main/java/de/igslandstuhl/database/api/Student.java
@@ -13,6 +13,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.api.results.StudentGenerationResult;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
@@ -169,7 +170,7 @@ public static Student get(int id) {
             student.fetchTasks();
             return student;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Student with id {} from database", id, e);
             return null;
         }
     }
@@ -190,7 +191,7 @@ public static Student getByEmail(String email) {
         } catch (NullPointerException e) {
             return null;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Student with email {} from database", email, e);
             return null;
         }
     }
@@ -210,7 +211,7 @@ public static List<Student> getAll() {
                 "get_all_students", SQL_FIELDS
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve student list from database", e);
         }
         return studentIDs.stream()
             .map(Student::get)
@@ -247,7 +248,7 @@ public static String[] generatePasswords(int count, int length) {
             try {
                 Thread.sleep(new Random().nextInt(1,10)); // Sleep to ensure different seeds
             } catch (InterruptedException e) {
-                e.printStackTrace();
+                Application.LOGGER_API.error("Thread sleep while generating passwords was interrupted", e);
             }
         }
         return passwords;
@@ -581,7 +582,7 @@ private void loadCurrentTopics() {
                 }
             }
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to load current topics for '{}'", this.email, e);
         }
     }
 

diff --git a/src/main/java/de/igslandstuhl/database/api/Subject.java b/src/main/java/de/igslandstuhl/database/api/Subject.java
@@ -9,6 +9,7 @@
 import java.util.Objects;
 import java.util.stream.Collectors;
 
+import de.igslandstuhl.database.Application;
 import de.igslandstuhl.database.server.Server;
 import de.igslandstuhl.database.server.sql.SQLHelper;
 
@@ -94,7 +95,7 @@ public static Subject get(int id) {
             subjects.put(id, subject);
             return subject;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Subject with id {} from database", id, e);
             return null;
         }
     }
@@ -116,7 +117,7 @@ public static Subject get(String name) {
             subjects.put(subject.getId(), subject);
             return subject;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Subject with name {} from database", name, e);
             return null;
         }
     }
@@ -137,7 +138,7 @@ public static List<Subject> getAll() {
                 SQL_FIELDS
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve subject list from database", e);
         }
         return subjectIds.stream()
             .map(Subject::get)
@@ -199,7 +200,7 @@ public List<Topic> getTopics(int grade) {
                 String.valueOf(id)
             );
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve topic list for subject '{}' in grade {} from database", this.name, grade, e);
         }
         return topicIds.stream()
         .map(Topic::get)
@@ -218,7 +219,7 @@ public int[] getGrades() {
             new String[] {"grade"}, 
             String.valueOf(id));
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to retrieve list of available grades for subject '{}' from database", this.name, e);
         }
         return grades.stream().mapToInt(Integer::intValue).toArray();
     }
@@ -242,8 +243,7 @@ public void delete() throws SQLException {
                 try {
                     t.delete();
                 } catch (SQLException e) {
-                    e.printStackTrace();
-                    throw new IllegalStateException(e);
+                    throw new IllegalStateException("Failed to delete topic " + t.getName() + " which is necessary to delete subject " + this.name, e);
                 }
             }));
         } catch (IllegalStateException e) {

diff --git a/src/main/java/de/igslandstuhl/database/api/Task.java b/src/main/java/de/igslandstuhl/database/api/Task.java
@@ -180,7 +180,7 @@ public static Task get(int id) {
             tasks.put(id, task);
             return task;
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Task with id {} from database", id, e);
             return null;
         }
     }
@@ -194,7 +194,7 @@ public static List<Task> getByName(String name) {
             String[][] table = Server.getInstance().processRequest("get_tasks_by_name", new String[] {"id"}, name);
             Arrays.stream(table).map(s -> s[0]).map(Integer::parseInt).map(Task::get).forEach((t) -> t.getId()); // Do something because streams are lazy
         } catch (SQLException e) {
-            e.printStackTrace();
+            Application.LOGGER_API.error("Failed to get Task with name {} from database", name, e);
             return new ArrayList<>();
         }
         return tasks.values().stream()