migrated to jackson

build.gradle.kts

@@ -29,7 +29,6 @@ subprojects {
 
     dependencies {
         implementation(Annotations.id)
-        implementation(Gson.id)
 
         implementation(Log4j2.api)
         runtimeOnly(Log4j2.core)

buildSrc/src/main/kotlin/Dependencies.kt

@@ -33,11 +33,11 @@ object Mockito {
     const val jupiter = "$group:mockito-junit-jupiter:$version"
 }
 
-object Gson {
+object Jackson {
-    const val version = "2.8.8"
+    const val version = "2.13.1"
-    const val group = "com.google.code.gson"
 
-    const val id = "$group:gson:$version"
+    const val databind = "com.fasterxml.jackson.core:jackson-databind:$version"
+    const val module_parameter_names = "com.fasterxml.jackson.module:jackson-module-parameter-names:$version"
 }
 
 object Annotations {

wizard-client/wizard-client-cli/src/main/java/eu/jonahbauer/wizard/client/cli/state/Game.java

@@ -76,7 +76,7 @@ public final class Game extends BaseState {
                     }
                 }
             } else if (observerMessage instanceof HandMessage hand) {
-                hands.put(hand.getPlayer(), hand.getHand());
+                hands.put(hand.getPlayer(), new ArrayList<>(hand.getHand()));
                 if (hand.getPlayer().equals(self)) {
                     client.printfln("Your hand cards are: %s", hand.getHand());
                 } else {

wizard-client/wizard-client-libgdx/core/src/main/java/eu/jonahbauer/wizard/client/libgdx/state/Game.java

@@ -172,7 +172,7 @@ public final class Game extends BaseState {
         if (juggling) checkActivePlayer(player, JUGGLE_CARD);
         finishInteraction();
 
-        hands.put(player, hand);
+        hands.put(player, new ArrayList<>(hand));
         gameScreen.setSelectedCard(null);
         gameScreen.setHand(player, hand, juggling);
         juggling = false;

wizard-common/build.gradle.kts

@@ -0,0 +1,10 @@
+val implementation by configurations
+
+dependencies {
+    implementation(Jackson.databind)
+    implementation(Jackson.module_parameter_names)
+}
+
+tasks.withType<JavaCompile> {
+    options.compilerArgs.add("-parameters")
+}

wizard-common/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java

@@ -1,273 +0,0 @@
-/*
- * Copyright (C) 2011 Google Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.google.gson.typeadapters;
-
-import com.google.gson.*;
-import com.google.gson.reflect.TypeToken;
-import com.google.gson.stream.JsonReader;
-import com.google.gson.stream.JsonWriter;
-
-import java.io.IOException;
-import java.util.LinkedHashMap;
-import java.util.Map;
-
-/**
- * Adapts values whose runtime type may differ from their declaration type. This
- * is necessary when a field's type is not the same type that GSON should create
- * when deserializing that field. For example, consider these types:
- * <pre>   {@code
- *   abstract class Shape {
- *     int x;
- *     int y;
- *   }
- *   class Circle extends Shape {
- *     int radius;
- *   }
- *   class Rectangle extends Shape {
- *     int width;
- *     int height;
- *   }
- *   class Diamond extends Shape {
- *     int width;
- *     int height;
- *   }
- *   class Drawing {
- *     Shape bottomShape;
- *     Shape topShape;
- *   }
- * }</pre>
- * <p>Without additional type information, the serialized JSON is ambiguous. Is
- * the bottom shape in this drawing a rectangle or a diamond? <pre>   {@code
- *   {
- *     "bottomShape": {
- *       "width": 10,
- *       "height": 5,
- *       "x": 0,
- *       "y": 0
- *     },
- *     "topShape": {
- *       "radius": 2,
- *       "x": 4,
- *       "y": 1
- *     }
- *   }}</pre>
- * This class addresses this problem by adding type information to the
- * serialized JSON and honoring that type information when the JSON is
- * deserialized: <pre>   {@code
- *   {
- *     "bottomShape": {
- *       "type": "Diamond",
- *       "width": 10,
- *       "height": 5,
- *       "x": 0,
- *       "y": 0
- *     },
- *     "topShape": {
- *       "type": "Circle",
- *       "radius": 2,
- *       "x": 4,
- *       "y": 1
- *     }
- *   }}</pre>
- * Both the type field name ({@code "type"}) and the type labels ({@code
- * "Rectangle"}) are configurable.
- *
- * <h3>Registering Types</h3>
- * Create a {@code RuntimeTypeAdapterFactory} by passing the base type and type field
- * name to the {@link #of} factory method. If you don't supply an explicit type
- * field name, {@code "type"} will be used. <pre>   {@code
- *   RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory
- *       = RuntimeTypeAdapterFactory.of(Shape.class, "type");
- * }</pre>
- * Next register all of your subtypes. Every subtype must be explicitly
- * registered. This protects your application from injection attacks. If you
- * don't supply an explicit type label, the type's simple name will be used.
- * <pre>   {@code
- *   shapeAdapterFactory.registerSubtype(Rectangle.class, "Rectangle");
- *   shapeAdapterFactory.registerSubtype(Circle.class, "Circle");
- *   shapeAdapterFactory.registerSubtype(Diamond.class, "Diamond");
- * }</pre>
- * Finally, register the type adapter factory in your application's GSON builder:
- * <pre>   {@code
- *   Gson gson = new GsonBuilder()
- *       .registerTypeAdapterFactory(shapeAdapterFactory)
- *       .create();
- * }</pre>
- * Like {@code GsonBuilder}, this API supports chaining: <pre>   {@code
- *   RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class)
- *       .registerSubtype(Rectangle.class)
- *       .registerSubtype(Circle.class)
- *       .registerSubtype(Diamond.class);
- * }</pre>
- *
- * <h3>Serialization and deserialization</h3>
- * In order to serialize and deserialize a polymorphic object,
- * you must specify the base type explicitly.
- * <pre>   {@code
- *   Diamond diamond = new Diamond();
- *   String json = gson.toJson(diamond, Shape.class);
- * }</pre>
- * And then:
- * <pre>   {@code
- *   Shape shape = gson.fromJson(json, Shape.class);
- * }</pre>
- */
-@SuppressWarnings("ALL")
-public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
-  private final Class<?> baseType;
-  private final String typeFieldName;
-  private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<>();
-  private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<>();
-  private final boolean maintainType;
-
-  private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boolean maintainType) {
-    if (typeFieldName == null || baseType == null) {
-      throw new NullPointerException();
-    }
-    this.baseType = baseType;
-    this.typeFieldName = typeFieldName;
-    this.maintainType = maintainType;
-  }
-
-  /**
-   * Creates a new runtime type adapter using for {@code baseType} using {@code
-   * typeFieldName} as the type field name. Type field names are case sensitive.
-   * {@code maintainType} flag decide if the type will be stored in pojo or not.
-   */
-  public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName, boolean maintainType) {
-    return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, maintainType);
-  }
-  
-  /**
-   * Creates a new runtime type adapter using for {@code baseType} using {@code
-   * typeFieldName} as the type field name. Type field names are case sensitive.
-   */
-  public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName) {
-    return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, false);
-  }
-
-  /**
-   * Creates a new runtime type adapter for {@code baseType} using {@code "type"} as
-   * the type field name.
-   */
-  public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType) {
-    return new RuntimeTypeAdapterFactory<>(baseType, "type", false);
-  }
-
-  /**
-   * Registers {@code type} identified by {@code label}. Labels are case
-   * sensitive.
-   *
-   * @throws IllegalArgumentException if either {@code type} or {@code label}
-   *     have already been registered on this type adapter.
-   */
-  public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type, String label) {
-    if (type == null || label == null) {
-      throw new NullPointerException();
-    }
-    if (subtypeToLabel.containsKey(type) || labelToSubtype.containsKey(label)) {
-      throw new IllegalArgumentException("types and labels must be unique");
-    }
-    labelToSubtype.put(label, type);
-    subtypeToLabel.put(type, label);
-    return this;
-  }
-
-  /**
-   * Registers {@code type} identified by its {@link Class#getSimpleName simple
-   * name}. Labels are case sensitive.
-   *
-   * @throws IllegalArgumentException if either {@code type} or its simple name
-   *     have already been registered on this type adapter.
-   */
-  public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type) {
-    return registerSubtype(type, type.getSimpleName());
-  }
-
-  @Override
-  public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
-    if (type.getRawType() != baseType) {
-      return null;
-    }
-
-    final TypeAdapter<JsonElement> jsonElementAdapter = gson.getAdapter(JsonElement.class);
-    final Map<String, TypeAdapter<?>> labelToDelegate
-        = new LinkedHashMap<>();
-    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate
-        = new LinkedHashMap<>();
-    for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
-      TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
-      labelToDelegate.put(entry.getKey(), delegate);
-      subtypeToDelegate.put(entry.getValue(), delegate);
-    }
-
-    return new TypeAdapter<R>() {
-      @Override public R read(JsonReader in) throws IOException {
-        JsonElement jsonElement = jsonElementAdapter.read(in);
-        JsonElement labelJsonElement;
-        if (maintainType) {
-            labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName);
-        } else {
-            labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
-        }
-        
-        if (labelJsonElement == null) {
-          throw new JsonParseException("cannot deserialize " + baseType
-              + " because it does not define a field named " + typeFieldName);
-        }
-        String label = labelJsonElement.getAsString();
-        @SuppressWarnings("unchecked") // registration requires that subtype extends T
-        TypeAdapter<R> delegate = (TypeAdapter<R>) labelToDelegate.get(label);
-        if (delegate == null) {
-          throw new JsonParseException("cannot deserialize " + baseType + " subtype named "
-              + label + "; did you forget to register a subtype?");
-        }
-        return delegate.fromJsonTree(jsonElement);
-      }
-
-      @Override public void write(JsonWriter out, R value) throws IOException {
-        Class<?> srcType = value.getClass();
-        String label = subtypeToLabel.get(srcType);
-        @SuppressWarnings("unchecked") // registration requires that subtype extends T
-        TypeAdapter<R> delegate = (TypeAdapter<R>) subtypeToDelegate.get(srcType);
-        if (delegate == null) {
-          throw new JsonParseException("cannot serialize " + srcType.getName()
-              + "; did you forget to register a subtype?");
-        }
-        JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject();
-
-        if (maintainType) {
-          jsonElementAdapter.write(out, jsonObject);
-          return;
-        }
-
-        JsonObject clone = new JsonObject();
-
-        if (jsonObject.has(typeFieldName)) {
-          throw new JsonParseException("cannot serialize " + srcType.getName()
-              + " because it already defines a field named " + typeFieldName);
-        }
-        clone.add(typeFieldName, new JsonPrimitive(label));
-        
-        for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
-          clone.add(e.getKey(), e.getValue());
-        }
-        jsonElementAdapter.write(out, clone);
-      }
-    }.nullSafe();
-  }
-}

wizard-common/src/main/java/eu/jonahbauer/wizard/common/messages/ParseException.java

@@ -0,0 +1,7 @@
+package eu.jonahbauer.wizard.common.messages;
+
+public class ParseException extends RuntimeException {
+    public ParseException(Throwable cause) {
+        super(cause);
+    }
+}

wizard-common/src/main/java/eu/jonahbauer/wizard/common/messages/client/ClientMessage.java

@@ -1,25 +1,23 @@
 package eu.jonahbauer.wizard.common.messages.client;
 
-import com.google.gson.Gson;
+import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.gson.GsonBuilder;
+import eu.jonahbauer.wizard.common.messages.ParseException;
-import com.google.gson.JsonParseException;
 import eu.jonahbauer.wizard.common.messages.player.PlayerMessage;
-import eu.jonahbauer.wizard.common.util.SealedClassTypeAdapterFactory;
+import eu.jonahbauer.wizard.common.util.SerializationUtil;
 import lombok.EqualsAndHashCode;
+import lombok.SneakyThrows;
 
 @EqualsAndHashCode
 public abstract sealed class ClientMessage permits CreateSessionMessage, InteractionMessage, JoinSessionMessage, LeaveSessionMessage, ReadyMessage, RejoinMessage {
-    private static final Gson GSON = new GsonBuilder()
+    private static final ObjectMapper MAPPER = SerializationUtil.newObjectMapper(ClientMessage.class, PlayerMessage.class);
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(ClientMessage.class, "Message"))
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(PlayerMessage.class, "Message"))
-            .create();
 
-    public static ClientMessage parse(String json) throws JsonParseException {
+    public static ClientMessage parse(String json) throws ParseException {
-        return GSON.fromJson(json, ClientMessage.class);
+        return SerializationUtil.parse(json, MAPPER, ClientMessage.class);
     }
 
     @Override
+    @SneakyThrows
     public String toString() {
-        return GSON.toJson(this, ClientMessage.class);
+        return MAPPER.writeValueAsString(this);
     }
 }

wizard-common/src/main/java/eu/jonahbauer/wizard/common/messages/observer/ObserverMessage.java

@@ -1,23 +1,22 @@
 package eu.jonahbauer.wizard.common.messages.observer;
 
-import com.google.gson.Gson;
+import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.gson.GsonBuilder;
+import eu.jonahbauer.wizard.common.messages.ParseException;
-import com.google.gson.JsonParseException;
+import eu.jonahbauer.wizard.common.util.SerializationUtil;
-import eu.jonahbauer.wizard.common.util.SealedClassTypeAdapterFactory;
 import lombok.EqualsAndHashCode;
+import lombok.SneakyThrows;
 
 @EqualsAndHashCode
 public abstract sealed class ObserverMessage permits CardMessage, HandMessage, PredictionMessage, ScoreMessage, StateMessage, TimeoutMessage, TrickMessage, TrumpMessage, UserInputMessage {
-    private static final Gson GSON = new GsonBuilder()
+    private static final ObjectMapper MAPPER = SerializationUtil.newObjectMapper(ObserverMessage.class);
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(ObserverMessage.class, "Message"))
-            .create();
 
-    public static ObserverMessage parse(String json) throws JsonParseException {
+    public static ObserverMessage parse(String json) throws ParseException {
-        return GSON.fromJson(json, ObserverMessage.class);
+        return SerializationUtil.parse(json, MAPPER, ObserverMessage.class);
     }
 
     @Override
+    @SneakyThrows
     public String toString() {
-        return GSON.toJson(this, ObserverMessage.class);
+        return MAPPER.writeValueAsString(this);
     }
 }

wizard-common/src/main/java/eu/jonahbauer/wizard/common/messages/player/PlayerMessage.java

@@ -1,23 +1,22 @@
 package eu.jonahbauer.wizard.common.messages.player;
 
-import com.google.gson.Gson;
+import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.gson.GsonBuilder;
+import eu.jonahbauer.wizard.common.messages.ParseException;
-import com.google.gson.JsonParseException;
+import eu.jonahbauer.wizard.common.util.SerializationUtil;
-import eu.jonahbauer.wizard.common.util.SealedClassTypeAdapterFactory;
 import lombok.EqualsAndHashCode;
+import lombok.SneakyThrows;
 
 @EqualsAndHashCode
 public abstract sealed class PlayerMessage permits ContinueMessage, JuggleMessage, PickTrumpMessage, PlayCardMessage, PredictMessage {
-    private static final Gson GSON = new GsonBuilder()
+    private static final ObjectMapper MAPPER = SerializationUtil.newObjectMapper(PlayerMessage.class);
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(PlayerMessage.class, "Message"))
-            .create();
 
-    public static PlayerMessage parse(String json) throws JsonParseException {
+    public static PlayerMessage parse(String json) throws ParseException {
-        return GSON.fromJson(json, PlayerMessage.class);
+        return SerializationUtil.parse(json, MAPPER, PlayerMessage.class);
     }
 
     @Override
+    @SneakyThrows
     public String toString() {
-        return GSON.toJson(this);
+        return MAPPER.writeValueAsString(this);
     }
 }

wizard-common/src/main/java/eu/jonahbauer/wizard/common/messages/server/ServerMessage.java

@@ -1,25 +1,23 @@
 package eu.jonahbauer.wizard.common.messages.server;
 
-import com.google.gson.Gson;
+import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.gson.GsonBuilder;
+import eu.jonahbauer.wizard.common.messages.ParseException;
-import com.google.gson.JsonParseException;
 import eu.jonahbauer.wizard.common.messages.observer.ObserverMessage;
-import eu.jonahbauer.wizard.common.util.SealedClassTypeAdapterFactory;
+import eu.jonahbauer.wizard.common.util.SerializationUtil;
 import lombok.EqualsAndHashCode;
+import lombok.SneakyThrows;
 
 @EqualsAndHashCode
 public abstract sealed class ServerMessage permits AckMessage, GameMessage, KickVotedMessage, KickedMessage, NackMessage, PlayerLeftMessage, PlayerModifiedMessage, SessionJoinedMessage, SessionListMessage, SessionModifiedMessage, SessionRemovedMessage, StartingGameMessage {
-    private static final Gson GSON = new GsonBuilder()
+    private static final ObjectMapper MAPPER = SerializationUtil.newObjectMapper(ServerMessage.class, ObserverMessage.class);
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(ServerMessage.class, "Message"))
-            .registerTypeAdapterFactory(SealedClassTypeAdapterFactory.of(ObserverMessage.class, "Message"))
-            .create();
 
-    public static ServerMessage parse(String json) throws JsonParseException {
+    public static ServerMessage parse(String json) throws ParseException {
-        return GSON.fromJson(json, ServerMessage.class);
+        return SerializationUtil.parse(json, MAPPER, ServerMessage.class);
     }
 
     @Override
+    @SneakyThrows
     public String toString() {
-        return GSON.toJson(this, ServerMessage.class);
+        return MAPPER.writeValueAsString(this);
     }
 }

wizard-common/src/main/java/eu/jonahbauer/wizard/common/util/SealedClassTypeAdapterFactory.java

@@ -1,62 +0,0 @@
-package eu.jonahbauer.wizard.common.util;
-
-import com.google.gson.Gson;
-import com.google.gson.TypeAdapter;
-import com.google.gson.TypeAdapterFactory;
-import com.google.gson.reflect.TypeToken;
-import com.google.gson.typeadapters.RuntimeTypeAdapterFactory;
-import org.jetbrains.annotations.Nullable;
-
-import java.lang.reflect.Modifier;
-import java.util.Locale;
-
-public final class SealedClassTypeAdapterFactory<T> implements TypeAdapterFactory {
-    private final RuntimeTypeAdapterFactory<T> factory;
-
-    public static <T> SealedClassTypeAdapterFactory<T> of(Class<T> clazz) {
-        return new SealedClassTypeAdapterFactory<>(clazz, null);
-    }
-
-    public static <T> SealedClassTypeAdapterFactory<T> of(Class<T> clazz, @Nullable String suffix) {
-        return new SealedClassTypeAdapterFactory<>(clazz, suffix);
-    }
-
-    private SealedClassTypeAdapterFactory(Class<T> clazz, @Nullable String suffix) {
-        factory = RuntimeTypeAdapterFactory.of(clazz);
-        register(clazz, suffix);
-    }
-
-    private void register(Class<? extends T> clazz, String suffix) {
-        for (Class<?> subclass : clazz.getPermittedSubclasses()) {
-            int modifiers = subclass.getModifiers();
-            if (Modifier.isFinal(modifiers) || subclass.isSealed() && !Modifier.isAbstract(modifiers)) {
-                String name = subclass.getSimpleName();
-
-                // remove suffix
-                if (suffix != null) {
-                    if (name.endsWith(suffix)) name = name.substring(0, name.length() - suffix.length());
-                }
-
-                // transform camelCast to snake_case
-                name = name.replaceAll("([a-z])([A-Z]+)", "$1_$2").toLowerCase(Locale.ROOT);
-
-                factory.registerSubtype(subclass.asSubclass(clazz), name);
-            }
-            if (subclass.isSealed()) {
-                register(subclass.asSubclass(clazz), suffix);
-            } else if (!Modifier.isFinal(modifiers)) {
-                //subclass is non-sealed
-                throw new IllegalArgumentException(
-                        "SealedClassTypeAdapterFactory does not support a type hierarchy that contains non-sealed classes. " +
-                        "Found non-sealed class " + subclass.getName()
-                );
-            }
-        }
-
-    }
-
-    @Override
-    public <S> TypeAdapter<S> create(Gson gson, TypeToken<S> type) {
-        return factory.create(gson, type);
-    }
-}

wizard-common/src/main/java/eu/jonahbauer/wizard/common/util/SerializationUtil.java

@@ -0,0 +1,87 @@
+package eu.jonahbauer.wizard.common.util;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.cfg.MapperConfig;
+import com.fasterxml.jackson.databind.introspect.*;
+import com.fasterxml.jackson.databind.jsontype.NamedType;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
+import eu.jonahbauer.wizard.common.messages.ParseException;
+import lombok.experimental.UtilityClass;
+
+import java.lang.reflect.Modifier;
+import java.util.Locale;
+
+@UtilityClass
+public class SerializationUtil {
+    public static ObjectMapper newObjectMapper(Class<?>...classes) {
+        var mapper = new ObjectMapper()
+                .registerModule(new ParameterNamesModule(JsonCreator.Mode.PROPERTIES))
+                .registerModule(new SimpleModule() {
+                    @Override
+                    public void setupModule(SetupContext context) {
+                        super.setupModule(context);
+                        for (Class<?> clazz : classes) {
+                            context.setMixInAnnotations(clazz, Mixin.class);
+                        }
+                        context.insertAnnotationIntrospector(new NopAnnotationIntrospector() {
+                            @Override
+                            public JsonCreator.Mode findCreatorAnnotation(MapperConfig<?> config, Annotated ann) {
+                                if (ann instanceof AnnotatedConstructor con) {
+                                    var declaringClass = con.getDeclaringClass();
+                                    for (Class<?> clazz : classes) {
+                                        if (clazz.isAssignableFrom(declaringClass)) {
+                                            return JsonCreator.Mode.PROPERTIES;
+                                        }
+                                    }
+                                }
+                                return super.findCreatorAnnotation(config, ann);
+                            }
+                        });
+                    }
+                });
+
+        for (Class<?> clazz : classes) {
+            registerSubtypes(mapper, clazz);
+        }
+
+        return mapper;
+    }
+
+    private static void registerSubtypes(ObjectMapper objectMapper, Class<?> clazz) {
+        if (!clazz.isSealed()) throw new IllegalArgumentException();
+
+        var suffix = "Message";
+        for (Class<?> subclass : clazz.getPermittedSubclasses()) {
+            int modifiers = subclass.getModifiers();
+
+            if (Modifier.isFinal(modifiers) || subclass.isSealed() && !Modifier.isAbstract(modifiers)) {
+                var name = subclass.getSimpleName();
+                if (name.endsWith(suffix)) name = name.substring(0, name.length() - suffix.length());
+                name = name.replaceAll("([a-z])([A-Z]+)", "$1_$2").toLowerCase(Locale.ROOT);
+
+                objectMapper.registerSubtypes(new NamedType(subclass, name));
+            }
+
+            if (subclass.isSealed()) {
+                registerSubtypes(objectMapper, subclass);
+            } else if (!Modifier.isFinal(modifiers)) {
+                throw new IllegalArgumentException("Non-sealed classes are not supported.");
+            }
+        }
+    }
+
+    public static <T> T parse(String json, ObjectMapper objectMapper, Class<T> clazz) throws ParseException {
+        try {
+            return objectMapper.readValue(json, clazz);
+        } catch (JsonProcessingException e) {
+            throw new ParseException(e);
+        }
+    }
+
+    @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
+    private static class Mixin {}
+}

wizard-server/src/main/java/eu/jonahbauer/wizard/server/socket/WizardSocketHandler.java

@@ -1,6 +1,6 @@
 package eu.jonahbauer.wizard.server.socket;
 
-import com.google.gson.JsonParseException;
+import eu.jonahbauer.wizard.common.messages.ParseException;
 import eu.jonahbauer.wizard.common.messages.client.ClientMessage;
 import eu.jonahbauer.wizard.common.messages.server.NackMessage;
 import eu.jonahbauer.wizard.server.NackException;
@@ -37,7 +37,7 @@ public class WizardSocketHandler extends TextWebSocketHandler {
             player.onMessage(ClientMessage.parse(text.getPayload()));
         } catch (NackException e) {
             player.send(e.toMessage());
-        } catch (JsonParseException e) {
+        } catch (ParseException e) {
             player.send(new NackMessage(NackMessage.MALFORMED_MESSAGE, "Could not parse " + text.getPayload() + "."));
         }
     }