src/de/steamwar/command/AbstractGuardChecker.java

@@ -19,6 +19,7 @@
 
 package de.steamwar.command;
 
+@Deprecated
 @FunctionalInterface
 public interface AbstractGuardChecker<T> {
     /**

src/de/steamwar/command/AbstractSWCommand.java

@@ -38,6 +38,7 @@ public abstract class AbstractSWCommand<T> {
 
     private final Map<String, AbstractTypeMapper<T, ?>> localTypeMapper = new HashMap<>();
     private final Map<String, AbstractGuardChecker<T>> localGuardChecker = new HashMap<>();
+    private final Map<String, AbstractValidator<T, ?>> localValidators = new HashMap<>();
 
     protected AbstractSWCommand(Class<T> clazz, String command) {
         this(clazz, command, new String[0]);
@@ -64,11 +65,15 @@ public abstract class AbstractSWCommand<T> {
         System.out.println(message.get());
     }
 
+    protected void sendMessage(T sender, String message, Object[] args) {}
+
     protected final void execute(T sender, String alias, String[] args) {
         initialize();
+        List<Runnable> errors = new ArrayList<>();
         try {
-            if (!commandList.stream().anyMatch(s -> s.invoke(sender, alias, args))) {
-                commandHelpList.stream().anyMatch(s -> s.invoke(sender, alias, args));
+            if (!commandList.stream().anyMatch(s -> s.invoke(errors::add, sender, alias, args))) {
+                errors.forEach(Runnable::run);
+                commandHelpList.stream().anyMatch(s -> s.invoke((ignore) -> {}, sender, alias, args));
             }
         } catch (CommandNoHelpException e) {
             // Ignored
@@ -127,6 +132,20 @@ public abstract class AbstractSWCommand<T> {
                     SWCommandUtils.getGUARD_FUNCTIONS().putIfAbsent(anno.value().getTypeName(), guardChecker);
                 }
             });
+            addValidator(Validator.class, method, i -> i == 0, false, AbstractValidator.class, (anno, validator) -> {
+                if (anno.local()) {
+                    localValidators.putIfAbsent(anno.value(), (AbstractValidator<T, ?>) validator);
+                } else {
+                    SWCommandUtils.getVALIDATOR_FUNCTIONS().putIfAbsent(anno.value(), validator);
+                }
+            });
+            addValidator(ClassValidator.class, method, i -> i == 0, false, AbstractValidator.class, (anno, validator) -> {
+                if (anno.local()) {
+                    localValidators.putIfAbsent(anno.value().getTypeName(), (AbstractValidator<T, ?>) validator);
+                } else {
+                    SWCommandUtils.getVALIDATOR_FUNCTIONS().putIfAbsent(anno.value().getTypeName(), validator);
+                }
+            });
         }
         for (Method method : methods) {
             add(Register.class, method, i -> i > 0, true, null, (anno, parameters) -> {
@@ -141,7 +160,7 @@ public abstract class AbstractSWCommand<T> {
                     commandSystemWarning(() -> "The method '" + method.toString() + "' is lacking the varArgs parameters of type '" + String.class.getTypeName() + "' as last Argument");
                     return;
                 }
-                commandHelpList.add(new SubCommand<>(this, method, anno.value(), new HashMap<>(), localGuardChecker, true, null, anno.noTabComplete()));
+                commandHelpList.add(new SubCommand<>(this, method, anno.value(), new HashMap<>(), new HashMap<>(), localGuardChecker, true, null, anno.noTabComplete()));
             });
 
             add(Register.class, method, i -> i > 0, true, null, (anno, parameters) -> {
@@ -162,7 +181,7 @@ public abstract class AbstractSWCommand<T> {
                         return;
                     }
                 }
-                commandList.add(new SubCommand<>(this, method, anno.value(), localTypeMapper, localGuardChecker, false, anno.description(), anno.noTabComplete()));
+                commandList.add(new SubCommand<>(this, method, anno.value(), localTypeMapper, localValidators, localGuardChecker, false, anno.description(), anno.noTabComplete()));
             });
         }
 
@@ -217,6 +236,18 @@ public abstract class AbstractSWCommand<T> {
         });
     }
 
+    private <T extends Annotation> void addValidator(Class<T> annotation, Method method, IntPredicate parameterTester, boolean firstParameter, Class<?> returnType, BiConsumer<T, AbstractValidator<T, ?>> consumer) {
+        add(annotation, method, parameterTester, firstParameter, returnType, (anno, parameters) -> {
+            try {
+                method.setAccessible(true);
+                consumer.accept(anno, (AbstractValidator<T, ?>) method.invoke(this));
+            } catch (Exception e) {
+                throw new SecurityException(e.getMessage(), e);
+            }
+        });
+    }
+
+    @Deprecated
     private <T extends Annotation> void addGuard(Class<T> annotation, Method method, IntPredicate parameterTester, boolean firstParameter, Class<?> returnType, BiConsumer<T, AbstractGuardChecker<?>> consumer) {
         add(annotation, method, parameterTester, firstParameter, returnType, (anno, parameters) -> {
             try {
@@ -280,6 +311,7 @@ public abstract class AbstractSWCommand<T> {
         boolean local() default false;
     }
 
+    @Deprecated
     @Retention(RetentionPolicy.RUNTIME)
     @Target({ElementType.PARAMETER, ElementType.METHOD})
     protected @interface Guard {
@@ -288,6 +320,7 @@ public abstract class AbstractSWCommand<T> {
         boolean local() default false;
     }
 
+    @Deprecated
     @Retention(RetentionPolicy.RUNTIME)
     @Target({ElementType.METHOD})
     protected @interface ClassGuard {
@@ -296,6 +329,22 @@ public abstract class AbstractSWCommand<T> {
         boolean local() default false;
     }
 
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target({ElementType.PARAMETER, ElementType.METHOD})
+    protected @interface Validator {
+        String value() default "";
+
+        boolean local() default false;
+    }
+
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target({ElementType.METHOD})
+    protected @interface ClassValidator {
+        Class<?> value();
+
+        boolean local() default false;
+    }
+
     @Retention(RetentionPolicy.RUNTIME)
     @Target({ElementType.PARAMETER})
     protected @interface StaticValue {
@@ -320,4 +369,13 @@ public abstract class AbstractSWCommand<T> {
          */
         String value();
     }
+
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target({ElementType.PARAMETER})
+    protected @interface ErrorMessage {
+        /**
+         * Error message to be displayed when the parameter is invalid.
+         */
+        String value();
+    }
 }

src/de/steamwar/command/AbstractTypeMapper.java

@@ -20,12 +20,18 @@
 package de.steamwar.command;
 
 import java.util.Collection;
+import java.util.function.BiConsumer;
 
-public interface AbstractTypeMapper<K, T> {
+public interface AbstractTypeMapper<K, T> extends AbstractValidator<K, T> {
     /**
      * The CommandSender can be null!
      */
     T map(K sender, String[] previousArguments, String s);
 
+    @Override
+    default boolean validate(K sender, T value, BiConsumer<String, Object[]> messageSender) {
+        return true;
+    }
+
     Collection<String> tabCompletes(K sender, String[] previousArguments, String s);
 }

src/de/steamwar/command/AbstractValidator.java

@@ -0,0 +1,36 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.command;
+
+import java.util.function.BiConsumer;
+
+@FunctionalInterface
+public interface AbstractValidator<K, T> {
+
+    /**
+     * Validates the given value.
+     *
+     * @param sender The sender of the command.
+     * @param value The value to validate or null if mapping returned null.
+     * @param messageSender The message sender to send messages to the player. Never send messages directly to the player.
+     * @return The result of the validation.
+     */
+    boolean validate(K sender, T value, BiConsumer<String, Object[]> messageSender);
+}

src/de/steamwar/command/CommandPart.java

@@ -23,9 +23,11 @@ import lombok.AllArgsConstructor;
 import lombok.Setter;
 
 import java.lang.reflect.Array;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.function.Consumer;
 
 class CommandPart<T> {
 
@@ -37,7 +39,9 @@ class CommandPart<T> {
         private final Object value;
     }
 
+    private AbstractSWCommand<T> command;
     private AbstractTypeMapper<T, ?> typeMapper;
+    private AbstractValidator<T, Object> validator;
     private AbstractGuardChecker<T> guardChecker;
     private Class<?> varArgType;
     private String optional;
@@ -48,8 +52,10 @@ class CommandPart<T> {
     @Setter
     private boolean ignoreAsArgument = false;
 
-    public CommandPart(AbstractTypeMapper<T, ?> typeMapper, AbstractGuardChecker<T> guardChecker, Class<?> varArgType, String optional, GuardCheckType guardCheckType) {
+    public CommandPart(AbstractSWCommand<T> command, AbstractTypeMapper<T, ?> typeMapper, AbstractValidator<T, Object> validator, AbstractGuardChecker<T> guardChecker, Class<?> varArgType, String optional, GuardCheckType guardCheckType) {
+        this.command = command;
         this.typeMapper = typeMapper;
+        this.validator = validator;
         this.guardChecker = guardChecker;
         this.varArgType = varArgType;
         this.optional = optional;
@@ -82,11 +88,11 @@ class CommandPart<T> {
         }
     }
 
-    public void generateArgumentArray(List<Object> current, T sender, String[] args, int startIndex) {
+    public void generateArgumentArray(Consumer<Runnable> errors, List<Object> current, T sender, String[] args, int startIndex) {
         if (varArgType != null) {
             Object array = Array.newInstance(varArgType, args.length - startIndex);
             for (int i = startIndex; i < args.length; i++) {
-                CheckArgumentResult validArgument = checkArgument(null, sender, args, i);
+                CheckArgumentResult validArgument = checkArgument(errors, null, sender, args, i);
                 if (!validArgument.success) {
                     throw new CommandParseException();
                 }
@@ -96,7 +102,7 @@ class CommandPart<T> {
             return;
         }
 
-        CheckArgumentResult validArgument = checkArgument(null, sender, args, startIndex);
+        CheckArgumentResult validArgument = checkArgument(errors, null, sender, args, startIndex);
         if (!validArgument.success && optional == null) {
             throw new CommandParseException();
         }
@@ -105,7 +111,7 @@ class CommandPart<T> {
                 current.add(typeMapper.map(sender, EMPTY_ARRAY, optional));
             }
             if (next != null) {
-                next.generateArgumentArray(current, sender, args, startIndex);
+                next.generateArgumentArray(errors, current, sender, args, startIndex);
             }
             return;
         }
@@ -113,7 +119,7 @@ class CommandPart<T> {
             current.add(validArgument.value);
         }
         if (next != null) {
-            next.generateArgumentArray(current, sender, args, startIndex + 1);
+            next.generateArgumentArray(errors, current, sender, args, startIndex + 1);
         }
     }
 
@@ -153,7 +159,7 @@ class CommandPart<T> {
     public void generateTabComplete(List<String> current, T sender, String[] args, int startIndex) {
         if (varArgType != null) {
             for (int i = startIndex; i < args.length - 1; i++) {
-                CheckArgumentResult validArgument = checkArgument(GuardCheckType.TAB_COMPLETE, sender, args, i);
+                CheckArgumentResult validArgument = checkArgument((ignore) -> {}, GuardCheckType.TAB_COMPLETE, sender, args, i);
                 if (!validArgument.success) {
                     return;
                 }
@@ -166,7 +172,7 @@ class CommandPart<T> {
         }
 
         if (args.length - 1 > startIndex) {
-            CheckArgumentResult checkArgumentResult = checkArgument(GuardCheckType.TAB_COMPLETE, sender, args, startIndex);
+            CheckArgumentResult checkArgumentResult = checkArgument((ignore) -> {}, GuardCheckType.TAB_COMPLETE, sender, args, startIndex);
             if (checkArgumentResult.success && next != null) {
                 next.generateTabComplete(current, sender, args, startIndex + 1);
                 return;
@@ -186,12 +192,23 @@ class CommandPart<T> {
         }
     }
 
-    private CheckArgumentResult checkArgument(GuardCheckType guardCheckType, T sender, String[] args, int index) {
+    private CheckArgumentResult checkArgument(Consumer<Runnable> errors, GuardCheckType guardCheckType, T sender, String[] args, int index) {
         try {
             Object value = typeMapper.map(sender, Arrays.copyOf(args, index), args[index]);
+            if (validator != null) {
+                if (!validator.validate(sender, value, (s, objects) -> {
+                    errors.accept(() -> {
+                        command.sendMessage(sender, s, objects);
+                    });
+                })) {
+                    return new CheckArgumentResult(false, null);
+                }
+                return new CheckArgumentResult(value != null, value);
+            }
             if (value == null) {
                 return new CheckArgumentResult(false, null);
             }
+
             GuardResult guardResult = checkGuard(guardCheckType, sender, args, index);
             switch (guardResult) {
                 case ALLOWED:

src/de/steamwar/command/GuardCheckType.java

@@ -19,6 +19,7 @@
 
 package de.steamwar.command;
 
+@Deprecated
 public enum GuardCheckType {
     COMMAND,
     HELP_COMMAND,

src/de/steamwar/command/GuardResult.java

@@ -19,6 +19,7 @@
 
 package de.steamwar.command;
 
+@Deprecated
 public enum GuardResult {
     ALLOWED,
     DENIED_WITH_HELP,

src/de/steamwar/command/SWCommandUtils.java

@@ -26,8 +26,10 @@ import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.lang.reflect.Parameter;
 import java.util.*;
+import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 @UtilityClass
 public class SWCommandUtils {
@@ -36,8 +38,12 @@ public class SWCommandUtils {
     private final Map<String, AbstractTypeMapper<?, ?>> MAPPER_FUNCTIONS = new HashMap<>();
 
     @Getter
+    @Deprecated
     private final Map<String, AbstractGuardChecker<?>> GUARD_FUNCTIONS = new HashMap<>();
 
+    @Getter
+    private final Map<String, AbstractValidator<?, ?>> VALIDATOR_FUNCTIONS = new HashMap<>();
+
     private SWTypeMapperCreator swTypeMapperCreator = (mapper, tabCompleter) -> new AbstractTypeMapper<Object, Object>() {
         @Override
         public Object map(Object sender, String[] previousArguments, String s) {
@@ -72,11 +78,11 @@ public class SWCommandUtils {
         MAPPER_FUNCTIONS.put(alternativeClazz.getTypeName(), mapper);
     }
 
-    static <T> CommandPart<T> generateCommandPart(boolean help, String[] subCommand, Parameter[] parameters, Map<String, AbstractTypeMapper<T, ?>> localTypeMapper, Map<String, AbstractGuardChecker<T>> localGuardChecker) {
+    static <T> CommandPart<T> generateCommandPart(AbstractSWCommand<T> command, boolean help, String[] subCommand, Parameter[] parameters, Map<String, AbstractTypeMapper<T, ?>> localTypeMapper, Map<String, AbstractValidator<T, ?>> localValidator, Map<String, AbstractGuardChecker<T>> localGuardChecker) {
         CommandPart<T> first = null;
         CommandPart<T> current = null;
         for (String s : subCommand) {
-            CommandPart commandPart = new CommandPart(createMapper(s), null, null, null, help ? GuardCheckType.HELP_COMMAND : GuardCheckType.COMMAND);
+            CommandPart commandPart = new CommandPart(command, createMapper(s), null, null, null, null, help ? GuardCheckType.HELP_COMMAND : GuardCheckType.COMMAND);
             commandPart.setIgnoreAsArgument(true);
             if (current != null) {
                 current.setNext(commandPart);
@@ -89,11 +95,12 @@ public class SWCommandUtils {
         for (int i = 1; i < parameters.length; i++) {
             Parameter parameter = parameters[i];
             AbstractTypeMapper<T, ?> typeMapper = getTypeMapper(parameter, localTypeMapper);
+            AbstractValidator<T, Object> validator = (AbstractValidator<T, Object>) getValidator(parameter, localValidator);
             AbstractGuardChecker<T> guardChecker = getGuardChecker(parameter, localGuardChecker);
             Class<?> varArgType = parameter.isVarArgs() ? parameter.getType().getComponentType() : null;
             AbstractSWCommand.OptionalValue optionalValue = parameter.getAnnotation(AbstractSWCommand.OptionalValue.class);
 
-            CommandPart<T> commandPart = new CommandPart<>(typeMapper, guardChecker, varArgType, optionalValue != null ? optionalValue.value() : null, help ? GuardCheckType.HELP_COMMAND : GuardCheckType.COMMAND);
+            CommandPart<T> commandPart = new CommandPart<>(command, typeMapper, validator, guardChecker, varArgType, optionalValue != null ? optionalValue.value() : null, help ? GuardCheckType.HELP_COMMAND : GuardCheckType.COMMAND);
             if (current != null) {
                 current.setNext(commandPart);
             }
@@ -114,7 +121,7 @@ public class SWCommandUtils {
         AbstractSWCommand.ClassMapper classMapper = parameter.getAnnotation(AbstractSWCommand.ClassMapper.class);
         AbstractSWCommand.Mapper mapper = parameter.getAnnotation(AbstractSWCommand.Mapper.class);
         if (clazz.isEnum() && classMapper == null && mapper == null && !MAPPER_FUNCTIONS.containsKey(clazz.getTypeName()) && !localTypeMapper.containsKey(clazz.getTypeName())) {
-            return (AbstractTypeMapper<T, ?>) createEnumMapper((Class<Enum<?>>) clazz);
+            return createEnumMapper((Class<Enum<?>>) clazz);
         }
 
         String name = clazz.getTypeName();
@@ -160,6 +167,47 @@ public class SWCommandUtils {
         return typeMapper;
     }
 
+    public static <T> AbstractValidator<T, ?> getValidator(Parameter parameter, Map<String, AbstractValidator<T, ?>> localValidator) {
+        Class<?> clazz = parameter.getType();
+        if (parameter.isVarArgs()) {
+            clazz = clazz.getComponentType();
+        }
+
+        AbstractSWCommand.ClassValidator classValidator = parameter.getAnnotation(AbstractSWCommand.ClassValidator.class);
+        if (classValidator != null) {
+            if (classValidator.value() != null) {
+                return getValidator(classValidator.value().getTypeName(), localValidator);
+            }
+            return getValidator(clazz.getTypeName(), localValidator);
+        }
+
+        AbstractSWCommand.Validator validator = parameter.getAnnotation(AbstractSWCommand.Validator.class);
+        if (validator != null) {
+            if (validator.value() != null && !validator.value().isEmpty()) {
+                return getValidator(validator.value(), localValidator);
+            }
+            return getValidator(clazz.getTypeName(), localValidator);
+        }
+
+        AbstractSWCommand.ErrorMessage errorMessage = parameter.getAnnotation(AbstractSWCommand.ErrorMessage.class);
+        if (errorMessage != null) {
+            return (AbstractValidator<T, String>) (sender, value, messageSender) -> {
+                if (value == null) messageSender.accept(errorMessage.value(), new Object[0]);
+                return value != null;
+            };
+        }
+        return null;
+    }
+
+    private static <T> AbstractValidator<T, ?> getValidator(String s, Map<String, AbstractValidator<T, ?>> localGuardChecker) {
+        AbstractValidator<T, ?> validator = localGuardChecker.getOrDefault(s, (AbstractValidator<T, ?>) VALIDATOR_FUNCTIONS.getOrDefault(s, null));
+        if (validator == null) {
+            throw new IllegalArgumentException("No validator found for " + s);
+        }
+        return validator;
+    }
+
+    @Deprecated
     public static <T> AbstractGuardChecker<T> getGuardChecker(Parameter parameter, Map<String, AbstractGuardChecker<T>> localGuardChecker) {
         Class<?> clazz = parameter.getType();
         if (parameter.isVarArgs()) {
@@ -184,6 +232,7 @@ public class SWCommandUtils {
         return null;
     }
 
+    @Deprecated
     private static <T> AbstractGuardChecker<T> getGuardChecker(String s, Map<String, AbstractGuardChecker<T>> localGuardChecker) {
         AbstractGuardChecker<T> guardChecker = localGuardChecker.getOrDefault(s, (AbstractGuardChecker<T>) GUARD_FUNCTIONS.getOrDefault(s, null));
         if (guardChecker == null) {
@@ -200,17 +249,28 @@ public class SWCommandUtils {
         MAPPER_FUNCTIONS.putIfAbsent(name, mapper);
     }
 
+    public static <T> void addValidator(Class<T> clazz, AbstractValidator<T, ?> validator) {
+        addValidator(clazz.getTypeName(), validator);
+    }
+
+    public static <T> void addValidator(String name, AbstractValidator<T, ?> validator) {
+        VALIDATOR_FUNCTIONS.putIfAbsent(name, validator);
+    }
+
+    @Deprecated
     public static <T> void addGuard(Class<?> clazz, AbstractGuardChecker<T> guardChecker) {
         addGuard(clazz.getTypeName(), guardChecker);
     }
 
+    @Deprecated
     public static <T> void addGuard(String name, AbstractGuardChecker<T> guardChecker) {
         GUARD_FUNCTIONS.putIfAbsent(name, guardChecker);
     }
 
     public static <T extends AbstractTypeMapper<K, String>, K> T createMapper(String... values) {
-        List<String> strings = Arrays.asList(values);
-        return createMapper((s) -> strings.contains(s) ? s : null, s -> strings);
+        List<String> strings = Arrays.stream(values).map(String::toLowerCase).collect(Collectors.toList());
+        List<String> tabCompletes = Arrays.asList(values);
+        return createMapper(s -> strings.contains(s.toLowerCase()) ? s : null, s -> tabCompletes);
     }
 
     public static <T extends AbstractTypeMapper<K, V>, K, V> T createMapper(Function<String, V> mapper, Function<String, Collection<String>> tabCompleter) {

src/de/steamwar/command/SubCommand.java

@@ -25,6 +25,7 @@ import java.lang.reflect.Parameter;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
@@ -36,13 +37,14 @@ public class SubCommand<T> {
     String[] subCommand;
     private Predicate<T> senderPredicate;
     private Function<T, ?> senderFunction;
+    AbstractValidator<T, T> validator;
     AbstractGuardChecker<T> guardChecker;
     boolean noTabComplete;
     int comparableValue;
 
     private CommandPart<T> commandPart;
 
-    SubCommand(AbstractSWCommand<T> abstractSWCommand, Method method, String[] subCommand, Map<String, AbstractTypeMapper<T, ?>> localTypeMapper, Map<String, AbstractGuardChecker<T>> localGuardChecker, boolean help, String[] description, boolean noTabComplete) {
+    SubCommand(AbstractSWCommand<T> abstractSWCommand, Method method, String[] subCommand, Map<String, AbstractTypeMapper<T, ?>> localTypeMapper, Map<String, AbstractValidator<T, ?>> localValidator, Map<String, AbstractGuardChecker<T>> localGuardChecker, boolean help, String[] description, boolean noTabComplete) {
         this.abstractSWCommand = abstractSWCommand;
         this.method = method;
         this.subCommand = subCommand;
@@ -52,15 +54,16 @@ public class SubCommand<T> {
         Parameter[] parameters = method.getParameters();
         comparableValue = parameters[parameters.length - 1].isVarArgs() ? Integer.MAX_VALUE : -parameters.length;
 
+        validator = (AbstractValidator<T, T>) SWCommandUtils.getValidator(parameters[0], localValidator);
         guardChecker = SWCommandUtils.getGuardChecker(parameters[0], localGuardChecker);
 
-        commandPart = SWCommandUtils.generateCommandPart(help, subCommand, parameters, localTypeMapper, localGuardChecker);
+        commandPart = SWCommandUtils.generateCommandPart(abstractSWCommand, help, subCommand, parameters, localTypeMapper, localValidator, localGuardChecker);
 
         senderPredicate = t -> parameters[0].getType().isAssignableFrom(t.getClass());
         senderFunction = t -> parameters[0].getType().cast(t);
     }
 
-    boolean invoke(T sender, String alias, String[] args) {
+    boolean invoke(Consumer<Runnable> errors, T sender, String alias, String[] args) {
         try {
             if (!senderPredicate.test(sender)) {
                 return false;
@@ -70,12 +73,36 @@ public class SubCommand<T> {
                 if (args.length != 0) {
                     return false;
                 }
+                if (validator != null) {
+                    if (!validator.validate(sender, sender, (s, objectArgs) -> {
+                        abstractSWCommand.sendMessage(sender, s, objectArgs);
+                    })) {
+                        throw new CommandNoHelpException();
+                    }
+                } else if (guardChecker != null) {
+                    GuardResult guardResult = guardChecker.guard(sender, GuardCheckType.COMMAND, new String[0], null);
+                    switch (guardResult) {
+                        case ALLOWED:
+                            break;
+                        case DENIED:
+                            throw new CommandNoHelpException();
+                        case DENIED_WITH_HELP:
+                        default:
+                            return true;
+                    }
+                }
                 method.setAccessible(true);
                 method.invoke(abstractSWCommand, senderFunction.apply(sender));
             } else {
                 List<Object> objects = new ArrayList<>();
-                commandPart.generateArgumentArray(objects, sender, args, 0);
-                if (guardChecker != null) {
+                commandPart.generateArgumentArray(errors, objects, sender, args, 0);
+                if (validator != null) {
+                    if (!validator.validate(sender, sender, (s, objectArgs) -> {
+                        abstractSWCommand.sendMessage(sender, s, objectArgs);
+                    })) {
+                        throw new CommandNoHelpException();
+                    }
+                } else if (guardChecker != null) {
                     GuardResult guardResult = guardChecker.guard(sender, GuardCheckType.COMMAND, new String[0], null);
                     switch (guardResult) {
                         case ALLOWED:
@@ -105,7 +132,13 @@ public class SubCommand<T> {
     }
 
     List<String> tabComplete(T sender, String[] args) {
-        if (guardChecker != null && guardChecker.guard(sender, GuardCheckType.TAB_COMPLETE, new String[0], null) != GuardResult.ALLOWED) {
+        if (validator != null) {
+            if (!validator.validate(sender, sender, (s, objects) -> {
+                // ignore
+            })) {
+                return null;
+            }
+        } else if (guardChecker != null && guardChecker.guard(sender, GuardCheckType.TAB_COMPLETE, new String[0], null) != GuardResult.ALLOWED) {
             return null;
         }
         if (commandPart == null) {

testsrc/de/steamwar/command/GuardCommandTest.java

@@ -35,7 +35,7 @@ public class GuardCommandTest {
         try {
             cmd.execute("test", "", new String[0]);
         } catch (Exception e) {
-            assertCMDFramework(e, ExecutionIdentifier.class, "RunTypeMapper");
+            assertThat(e.getMessage(), is("GuardChecker COMMAND"));
         }
     }
 

testsrc/de/steamwar/command/ValidatorCommand.java

@@ -0,0 +1,60 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.command;
+
+import de.steamwar.command.dto.ExecutionIdentifier;
+import de.steamwar.command.dto.TestSWCommand;
+import de.steamwar.command.dto.TestValidator;
+
+public class ValidatorCommand extends TestSWCommand {
+
+    public ValidatorCommand() {
+        super("testvalidator");
+    }
+
+    @Register
+    public void test(@Validator String sender) {
+        throw new ExecutionIdentifier("RunTest");
+    }
+
+    @Override
+    protected void sendMessage(String sender, String message, Object[] args) {
+        if (message.equals("Hello World")) {
+            throw new ExecutionIdentifier("RunSendMessageWithHelloWorldParameter");
+        }
+    }
+
+    @Register
+    public void onError(String sender, @ErrorMessage("Hello World") int error) {
+        throw new ExecutionIdentifier("RunOnError");
+    }
+
+    @Register
+    public void onError(String sender, double error) {
+        throw new ExecutionIdentifier("RunOnErrorDouble");
+    }
+
+    @ClassValidator(value = String.class, local = true)
+    public TestValidator<String> validator() {
+        return (sender, value, messageSender) -> {
+            throw new ExecutionIdentifier("RunValidator");
+        };
+    }
+}

testsrc/de/steamwar/command/ValidatorCommandTest.java

@@ -0,0 +1,63 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.command;
+
+import de.steamwar.command.dto.ExecutionIdentifier;
+import org.junit.Test;
+
+import static de.steamwar.AssertionUtils.assertCMDFramework;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+public class ValidatorCommandTest {
+
+    @Test
+    public void testValidator() {
+        ValidatorCommand cmd = new ValidatorCommand();
+        try {
+            cmd.execute("test", "", new String[0]);
+            assertThat(true, is(false));
+        } catch (Exception e) {
+            assertThat(e.getMessage(), is("RunValidator"));
+        }
+    }
+
+    @Test
+    public void testErrorMessage() {
+        ValidatorCommand cmd = new ValidatorCommand();
+        try {
+            cmd.execute("test", "", new String[]{"Hello"});
+            assertThat(true, is(false));
+        } catch (Exception e) {
+            assertThat(e.getMessage(), is("RunSendMessageWithHelloWorldParameter"));
+        }
+    }
+
+    @Test
+    public void testErrorNoMessage() {
+        ValidatorCommand cmd = new ValidatorCommand();
+        try {
+            cmd.execute("test", "", new String[]{"0.0"});
+            assertThat(true, is(false));
+        } catch (Exception e) {
+            assertCMDFramework(e, ExecutionIdentifier.class, "RunOnErrorDouble");
+        }
+    }
+}

testsrc/de/steamwar/command/dto/TestValidator.java

@@ -0,0 +1,25 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.command.dto;
+
+import de.steamwar.command.AbstractValidator;
+
+public interface TestValidator<T> extends AbstractValidator<String, T> {
+}