RESTful API for configuration

ccm-core/src/main/java/org/libreccm/api/admin/AdminApi.java

@@ -20,6 +20,7 @@ import org.libreccm.api.DefaultResponseHeaders;
 import org.libreccm.api.PreflightRequestFilter;
 import org.libreccm.api.admin.categorization.CategoriesApi;
 import org.libreccm.api.admin.categorization.DomainsApi;
+import org.libreccm.configuration.Configuration;
 
 /**
  *
@@ -40,6 +41,9 @@ public class AdminApi extends Application {
         classes.add(DomainsApi.class);
         classes.add(CategoriesApi.class);
 
+        // Configuration API
+        classes.add(Configuration.class);
+        
         // Security API
         classes.add(GroupsApi.class);
         classes.add(RolesApi.class);

ccm-core/src/main/java/org/libreccm/api/admin/configuration/BigDecimalConverter.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import java.math.BigDecimal;
+
+import javax.json.JsonNumber;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+class BigDecimalConverter implements SettingValueConverter<BigDecimal> {
+
+    @Override
+    public BigDecimal convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.NUMBER) {
+            return ((JsonNumber) value).bigDecimalValue();
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not a number.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/BooleanConverter.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+class BooleanConverter implements SettingValueConverter<Boolean> {
+
+    @Override
+    public Boolean convertSettingValue(final JsonValue value) {
+        switch(value.getValueType()) {
+            case FALSE:
+                return false;
+            case TRUE:
+                return true;
+            default:
+                throw new WebApplicationException(
+                "The provided value is not a boolean.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/ConfigurationApi.java

@@ -0,0 +1,296 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.libreccm.configuration.ConfigurationInfo;
+import org.libreccm.configuration.ConfigurationManager;
+import org.libreccm.configuration.SettingInfo;
+import org.libreccm.l10n.LocalizedString;
+
+import java.lang.reflect.Field;
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+import javax.enterprise.context.RequestScoped;
+import javax.inject.Inject;
+import javax.json.JsonValue;
+import javax.ws.rs.GET;
+import javax.ws.rs.PUT;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+@RequestScoped
+@Path("/configuration")
+public class ConfigurationApi {
+
+    private static final Logger LOGGER = LogManager.getLogger(
+        ConfigurationApi.class
+    );
+
+    @Inject
+    private ConfigurationManager confManager;
+
+    private final Map<String, SettingValueConverter<?>> converters;
+
+    public ConfigurationApi() {
+        converters = new HashMap<>();
+        converters.put(BigDecimal.class.getName(), new BigDecimalConverter());
+        converters.put(Boolean.class.getName(), new BooleanConverter());
+        converters.put(Double.class.getName(), new DoubleConverter());
+        converters.put(EnumConverter.class.getName(), new EnumConverter());
+        converters.put(
+            LocalizedString.class.getName(), new LocalizedStringConverter()
+        );
+        converters.put(Long.class.getName(), new LongConverter());
+        converters.put(String.class.getName(), new StringConverter());
+        converters.put(List.class.getName(), new StringListConverter());
+    }
+
+    @GET
+    @Path("/")
+    public List<ConfigurationInfo> getConfigurations() {
+        return confManager
+            .findAllConfigurations()
+            .stream()
+            .map(confManager::getConfigurationInfo)
+            .collect(Collectors.toList());
+    }
+
+    @GET
+    @Path("/{confName}")
+    public ConfigurationInfo getConfiguration(
+        @PathParam("confName") final String confName
+    ) {
+        final Class<?> clazz;
+        try {
+            clazz = Class.forName(confName);
+        } catch (ClassNotFoundException ex) {
+            throw new WebApplicationException(
+                String.format("No configuration %s available.", confName),
+                Response.Status.NOT_FOUND
+            );
+        }
+        try {
+            return confManager.getConfigurationInfo(clazz);
+        } catch (IllegalArgumentException ex) {
+            // We don't expose that we found a class for that name, but that 
+            // it is not an Configuration class.
+            throw new WebApplicationException(
+                String.format("No configuration %s available.", confName),
+                Response.Status.NOT_FOUND
+            );
+        }
+    }
+
+    @GET
+    @Path("/{confName}/{setting}")
+    @SuppressWarnings("unchecked")
+    public Object getSetting(
+        @PathParam("confName") final String confName,
+        @PathParam("setting") final String setting
+    ) {
+        final Class<?> clazz;
+        try {
+            clazz = Class.forName(confName);
+        } catch (ClassNotFoundException ex) {
+            throw new WebApplicationException(
+                String.format("No configuration %s available.", confName),
+                Response.Status.NOT_FOUND
+            );
+        }
+
+        final Object conf;
+        try {
+            conf = confManager.findConfiguration(clazz);
+        } catch (IllegalArgumentException ex) {
+            // We don't expose that we found a class for that name, but that 
+            // it is not an Configuration class.
+            throw new WebApplicationException(
+                String.format("No configuration %s available.", confName),
+                Response.Status.NOT_FOUND
+            );
+        }
+
+        final Field field;
+        try {
+            field = clazz.getDeclaredField(setting);
+        } catch (NoSuchFieldException ex) {
+            throw new WebApplicationException(
+                String.format(
+                    "The configuration \"%s\" has not setting \"%s\".",
+                    confName,
+                    setting
+                ),
+                Response.Status.NOT_FOUND
+            );
+        }
+
+        field.setAccessible(true);
+
+        try {
+            return field.get(conf);
+        } catch (IllegalAccessException | IllegalArgumentException ex) {
+            throw new WebApplicationException(
+                String.format(
+                    "Failed to retrieve setting \"%s\" "
+                        + "from configuration \"%s\"",
+                    setting,
+                    confName
+                )
+            );
+        }
+    }
+
+    @PUT
+    @Path("/{confName}/{setting}")
+    public Response updateSetting(
+        @PathParam("confName") final String confName,
+        @PathParam("setting") final String setting,
+        final JsonValue value
+    ) {
+        final Class<?> clazz;
+        try {
+            clazz = Class.forName(confName);
+        } catch (ClassNotFoundException ex) {
+            return Response
+                .status(Response.Status.NOT_FOUND)
+                .entity(
+                    String.format("No configuration %s available.", confName))
+                .build();
+        }
+
+        final Object conf;
+        try {
+            conf = confManager.findConfiguration(clazz);
+        } catch (IllegalArgumentException ex) {
+            // We don't expose that we found a class for that name, but that 
+            // it is not an Configuration class.
+            return Response
+                .status(Response.Status.NOT_FOUND)
+                .entity(
+                    String.format("No configuration %s available.", confName))
+                .build();
+        }
+
+        final Field field;
+        try {
+            field = clazz.getDeclaredField(setting);
+        } catch (NoSuchFieldException ex) {
+            return Response
+                .status(Response.Status.NOT_FOUND)
+                .entity(
+                    String.format(
+                        "The configuration \"%s\" has not setting \"%s\".",
+                        confName,
+                        setting
+                    )
+                )
+                .build();
+        }
+
+        field.setAccessible(true);
+
+        final ConfigurationInfo confInfo = confManager
+            .getConfigurationInfo(clazz);
+
+        final SettingInfo settingInfo = confInfo.getSettings().get(setting);
+        final String valueType = settingInfo.getValueType();
+        final SettingValueConverter<?> converter = converters.get(valueType);
+        if (converter == null) {
+            return Response.
+                status(Response.Status.INTERNAL_SERVER_ERROR)
+                .entity(
+                    String.format(
+                        "No converter available for type \"%s\" of "
+                            + "setting \"%s\" of configuration \"%s\".",
+                        valueType,
+                        setting,
+                        confName
+                    )
+                )
+                .build();
+        }
+
+        try {
+            field.set(conf, converter.convertSettingValue(value));
+        } catch (IllegalAccessException ex) {
+            LOGGER.error(
+                "Unable to set value of setting \"{}\" of "
+                    + "configuration \"{}\".",
+                setting,
+                confName
+            );
+            LOGGER.error(ex);
+            return Response
+                .status(Response.Status.INTERNAL_SERVER_ERROR)
+                .entity(
+                    String.format(
+                        "Unable to set value of setting \"%s\" of "
+                            + "configuration \"%s\".",
+                        setting,
+                        confName
+                    )
+                )
+                .build();
+        } catch (IllegalArgumentException ex) {
+            LOGGER.error(
+                "Provided value of type \"{}\" can't be used for "
+                    + "setting of type \"{}\".",
+                Objects.toString(value.getValueType()),
+                valueType
+            );
+            LOGGER.error(ex);
+            return Response
+                .status(Response.Status.INTERNAL_SERVER_ERROR)
+                .entity(
+                    String.format(
+                        "Provided value of type \"%s\" can't be used for "
+                            + "setting of type \"%s\".",
+                        Objects.toString(value.getValueType()),
+                        valueType
+                    )
+                )
+                .build();
+        }
+
+        return Response
+            .ok(
+                String.format(
+                    "Setting \"%s\" of configuration \"%s\" successfully "
+                        + "updated",
+                    setting,
+                    confName
+                )
+            )
+            .build();
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/DoubleConverter.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import javax.json.JsonNumber;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+class DoubleConverter implements SettingValueConverter<Double> {
+
+    @Override
+    public Double convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.NUMBER) {
+            return ((JsonNumber) value).doubleValue();
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not a number.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/EnumConverter.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import javax.json.JsonArray;
+import javax.json.JsonString;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+class EnumConverter
+    implements SettingValueConverter<Set<String>> {
+
+    @Override
+    public Set<String> convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.ARRAY) {
+            final JsonArray array = value.asJsonArray();
+            return array
+                .stream()
+                .map(this::convertEnumValue)
+                .collect(Collectors.toSet());
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not an array.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+    private String convertEnumValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.STRING) {
+            return ((JsonString) value).getString();
+        } else {
+            throw new WebApplicationException(
+                "One of the provided values is not a string.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/LocalizedStringConverter.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import org.libreccm.l10n.LocalizedString;
+
+import java.util.IllformedLocaleException;
+import java.util.Locale;
+import java.util.Map;
+
+import javax.json.JsonObject;
+import javax.json.JsonString;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public class LocalizedStringConverter
+    implements SettingValueConverter<LocalizedString> {
+
+    @Override
+    public LocalizedString convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.OBJECT) {
+            final JsonObject object = value.asJsonObject();
+            final LocalizedString localizedString = new LocalizedString();
+            object
+                .entrySet()
+                .stream()
+                .map(this::buildLocalizedValue)
+                .forEach(
+                    localized -> localizedString.addValue(
+                        localized.getLocale(),
+                        localized.getValue()
+                    )
+                );
+            return localizedString;
+        } else {
+            throw new WebApplicationException(
+                "One of the provided values is not an object.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+    private LocalizedValue buildLocalizedValue(
+        final Map.Entry<String, JsonValue> entry
+    ) {
+        final JsonValue value = entry.getValue();
+        if (value.getValueType() == JsonValue.ValueType.STRING) {
+            final Locale.Builder localeBuilder = new Locale.Builder();
+            final Locale locale;
+            try {
+                locale = new Locale.Builder()
+                    .setLanguageTag(entry.getKey())
+                    .build();
+            } catch (IllformedLocaleException ex) {
+                throw new WebApplicationException(
+                    String.format(
+                        "\"%s\" is not a valid locale.", entry.getKey()
+                    ),
+                    Response.Status.BAD_REQUEST
+                );
+            }
+            return new LocalizedValue(locale, ((JsonString) value).getString());
+        } else {
+            throw new WebApplicationException(
+                String.format(
+                    "Value for locale \"%s\" is not a string.",
+                    entry.getKey()
+                ),
+                Response.Status.BAD_REQUEST
+            );
+        }
+
+    }
+
+    private class LocalizedValue {
+
+        private final Locale locale;
+
+        private final String value;
+
+        public LocalizedValue(Locale locale, String value) {
+            this.locale = locale;
+            this.value = value;
+        }
+
+        public Locale getLocale() {
+            return locale;
+        }
+
+        public String getValue() {
+            return value;
+        }
+
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/LongConverter.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import javax.json.JsonNumber;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public class LongConverter implements SettingValueConverter<Long> {
+
+    @Override
+    public Long convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.NUMBER) {
+            return ((JsonNumber) value).longValue();
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not a number.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/SettingValueConverter.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import javax.json.JsonValue;
+
+/**
+ * Interface for the setting value converters.
+ * 
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ * @param <T> Value Type
+ */
+interface SettingValueConverter<T> {
+    
+    T convertSettingValue(JsonValue value);
+    
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/StringConverter.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import javax.json.JsonString;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+class StringConverter implements SettingValueConverter<String> {
+
+    @Override
+    public String convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.STRING) {
+            return ((JsonString) value).getString();
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not a string.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+
+}

ccm-core/src/main/java/org/libreccm/api/admin/configuration/StringListConverter.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2020 LibreCCM Foundation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301  USA
+ */
+package org.libreccm.api.admin.configuration;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import javax.json.JsonString;
+import javax.json.JsonValue;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+/**
+ *
+ * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
+ */
+public class StringListConverter implements SettingValueConverter<List<String>>{
+
+    @Override
+    public List<String> convertSettingValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.STRING)  {
+            return value
+                .asJsonArray()
+                .stream()
+                .map(this::convertValue)
+                .collect(Collectors.toList());
+        } else {
+            throw new WebApplicationException(
+                "The provided value is not an array.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+    
+    private String convertValue(final JsonValue value) {
+        if (value.getValueType() == JsonValue.ValueType.STRING) {
+            return ((JsonString) value).getString();
+        } else {
+            throw new WebApplicationException(
+                "One of the values in the array is not a string.",
+                Response.Status.BAD_REQUEST
+            );
+        }
+    }
+}

ccm-core/src/main/java/org/libreccm/configuration/ConfigurationManager.java

@@ -81,18 +81,23 @@ public class ConfigurationManager implements Serializable {
             CcmModule.class);
 
         final SortedSet<Class<?>> configurations = new TreeSet<>(
-            (conf1, conf2) -> conf1.getName().compareTo(conf2.getName()));
+            (conf1, conf2) -> conf1.getName().compareTo(conf2.getName())
+        );
 
         for (CcmModule module : modules) {
             final Module annotation = module.getClass().getAnnotation(
-                Module.class);
+                Module.class
+            );
 
             if (annotation == null) {
                 continue;
             }
 
             final List<Class<?>> moduleConfs = Arrays.stream(
-                annotation.configurations()).collect(Collectors.toList());
+                annotation.configurations()
+            ).collect(
+                Collectors.toList()
+            );
 
             configurations.addAll(moduleConfs);
         }

ccm-core/src/main/java/org/libreccm/configuration/EnumSetting.java

@@ -18,12 +18,22 @@
  */
 package org.libreccm.configuration;
 
-import javax.persistence.*;
 import java.io.Serializable;
-import java.util.*;
 
 import static org.libreccm.core.CoreConstants.DB_SCHEMA;
 
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+import javax.persistence.ElementCollection;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.JoinColumn;
+import javax.persistence.JoinTable;
+
 /**
  * A setting class for storing a set of strings. This can be used to generate
  * enums which can be configured by the administrator.