Initial commit (#340).

src/main/java/org/gitlab4j/api/ApplicationSettingsApi.java

+package org.gitlab4j.api;
+
+import java.text.ParseException;
+import java.util.Iterator;
+
+import javax.ws.rs.core.Response;
+
+import org.gitlab4j.api.models.Setting;
+import org.gitlab4j.api.models.ApplicationSettings;
+import org.gitlab4j.api.utils.ISO8601;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+/**
+ * This class implements the client side API for the GitLab Application Settings API.
+ * See <a href="https://docs.gitlab.com/ee/api/settings.html">Application Settings API at GitLab</a> for more information.
+ */
+public class ApplicationSettingsApi extends AbstractApi {
+
+    public ApplicationSettingsApi(GitLabApi gitLabApi) {
+        super(gitLabApi);
+    }
+
+    /**
+     * Get the current application settings of the GitLab instance.
+     *
+     * <pre><code>GitLab Endpoint: GET /api/v4/application/settings</code></pre>
+     *
+     * @return an ApplicationSettings instance containing the current application settings of the GitLab instance.
+     * @throws GitLabApiException if any exception occurs
+     */
+    public ApplicationSettings getApplicationSettings() throws GitLabApiException {
+
+        Response response = get(Response.Status.OK, null, "application", "settings");
+        JsonNode root = response.readEntity(JsonNode.class);
+        return (parseApplicationSettings(root));
+    }
+
+    /**
+     * Update the application settings of the GitLab instance with the settings in the 
+     * provided ApplicationSettings instance.
+     *
+     * <pre><code>GitLab Endpoint: PUT /api/v4/application/settings</code></pre>
+     *
+     * @param appSettings the ApplicationSettings instance holding the settings and values to update
+     * @return the updated application settings in an ApplicationSettings instance
+     * @throws GitLabApiException if any exception occurs
+     */
+    public ApplicationSettings updateApplicationSettings(ApplicationSettings appSettings) throws GitLabApiException {
+
+        if (appSettings == null || appSettings.getSettings().isEmpty()) {
+            throw new GitLabApiException("ApplicationSettings cannot be null or empty.");
+        }
+
+        final GitLabApiForm form = new GitLabApiForm();
+        appSettings.getSettings().forEach((s, v) -> form.withParam(s,  v));
+        Response response = put(Response.Status.OK, form.asMap(), "application", "settings");
+        JsonNode root = response.readEntity(JsonNode.class);
+        return (parseApplicationSettings(root));
+    }
+
+    /**
+     * Update a single application setting of the GitLab instance with the provided settings and value.
+     *
+     * <pre><code>GitLab Endpoint: PUT /api/v4/application/settings</code></pre>
+     *
+     * @param setting the ApplicationSetting to update
+     * @param value the new value for the application setting
+     * @return the updated application settings in an ApplicationSettings instance
+     * @throws GitLabApiException if any exception occurs
+     */
+    public ApplicationSettings updateApplicationSetting(Setting setting, Object value) throws GitLabApiException {
+
+        if (setting == null) {
+            throw new GitLabApiException("setting cannot be null.");
+        }
+
+        return (updateApplicationSetting(setting.toString(), value));
+    }
+
+    /**
+     * Update a single application setting of the GitLab instance with the provided settings and value.
+     *
+     * <pre><code>GitLab Endpoint: PUT /api/v4/application/settings</code></pre>
+     *
+     * @param setting the ApplicationSetting to update
+     * @param value the new value for the application setting
+     * @return the updated application settings in an ApplicationSettings instance
+     * @throws GitLabApiException if any exception occurs
+     */
+    public ApplicationSettings updateApplicationSetting(String setting, Object value) throws GitLabApiException {
+
+        if (setting == null || setting.trim().isEmpty()) {
+            throw new GitLabApiException("setting cannot be null or empty.");
+        }
+
+        GitLabApiForm form = new GitLabApiForm().withParam(setting, value);
+        Response response = put(Response.Status.OK, form.asMap(), "application", "settings");
+        JsonNode root = response.readEntity(JsonNode.class);
+        return (parseApplicationSettings(root));
+    }
+
+    /**
+     * Pareses the returned JSON and returns an ApplicationSettings instance.
+     *
+     * @param root the root JsonNode
+     * @return the populated ApplicationSettings instance
+     * @throws GitLabApiException if any error occurs
+     */
+    private final ApplicationSettings parseApplicationSettings(JsonNode root) throws GitLabApiException {
+
+        ApplicationSettings appSettings = new ApplicationSettings();
+
+        Iterator<String> fieldNames = root.fieldNames();
+        while (fieldNames.hasNext()) {
+
+            String fieldName = fieldNames.next();
+            switch (fieldName) {
+            case "id":
+                appSettings.setId(root.path(fieldName).asInt());
+                break;
+
+            case "created_at":
+                try {
+                    appSettings.setCreatedAt(ISO8601.toDate(root.path(fieldName).asText()));
+                } catch (ParseException pe) {
+                    throw new GitLabApiException(pe);
+                }
+                break;
+
+            case "updated_at":
+                try {
+                    appSettings.setUpdatedAt(ISO8601.toDate(root.path(fieldName).asText()));
+                } catch (ParseException pe) {
+                    throw new GitLabApiException(pe);
+                }
+                break;
+
+            default:
+
+                Setting setting = Setting.forValue(fieldName);
+                if (setting != null) {
+                    appSettings.addSetting(setting, root.path(fieldName));
+                } else {
+                    GitLabApi.getLogger().warning(String.format("Unknown setting: %s, type: %s",
+                            fieldName, root.path(fieldName).getClass().getSimpleName()));
+                    appSettings.addSetting(fieldName, root.path(fieldName));
+                }
+
+                break;
+            }
+        }
+
+        return (appSettings);
+    }
+}

src/main/java/org/gitlab4j/api/models/ApplicationSettings.java

+package org.gitlab4j.api.models;
+
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.gitlab4j.api.GitLabApiException;
+import org.gitlab4j.api.utils.JacksonJson;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.BooleanNode;
+import com.fasterxml.jackson.databind.node.DoubleNode;
+import com.fasterxml.jackson.databind.node.FloatNode;
+import com.fasterxml.jackson.databind.node.IntNode;
+import com.fasterxml.jackson.databind.node.NullNode;
+import com.fasterxml.jackson.databind.node.TextNode;
+
+public class ApplicationSettings {
+
+    private Integer id;
+    private Date createdAt;
+    private Date updatedAt;
+    private Map<String, Object> settings = new HashMap<>();
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public Date getCreatedAt() {
+        return createdAt;
+    }
+
+    public void setCreatedAt(Date createdAt) {
+        this.createdAt = createdAt;
+    }
+
+    public Date getUpdatedAt() {
+        return updatedAt;
+    }
+
+    public void setUpdatedAt(Date updatedAt) {
+        this.updatedAt = updatedAt;
+    }
+
+    public Map<String, Object> getSettings() {
+        return settings;
+    }
+
+    public void setSettings(Map<String, Object> settings) {
+        this.settings = settings;
+    }
+
+    @JsonIgnore
+    public Object getSetting(Setting setting) {
+
+        if (setting == null) {
+            return (null);
+        }
+
+        String name = setting.toString();
+        return (settings.get(name));
+    }
+
+    @JsonIgnore
+    public Object getSetting(String setting) {
+
+        if (setting == null) {
+            return (null);
+        }
+
+        return (settings.get(setting));
+    }
+
+    public Object addSetting(String setting, Object value) throws GitLabApiException {
+
+        Setting appSetting = Setting.forValue(setting);
+        if (appSetting != null) {
+            return (addSetting(appSetting, value));
+        }
+
+        settings.put(setting, value);
+        return (value);
+    }
+
+    public Object addSetting(Setting setting, Object value) throws GitLabApiException {
+
+        if (value instanceof JsonNode) {
+            value = jsonNodeToValue((JsonNode)value);
+        }
+
+        setting.validate(value);
+        settings.put(setting.toString(), value);
+        return (value);
+    }
+
+    public Object removeSetting(Setting setting) {
+        return settings.remove(setting.toString());
+    }
+
+    public Object removeSetting(String setting) {
+        return settings.remove(setting);
+    }
+
+    public void clearSettings() {
+        settings.clear();
+    }
+
+    private Object jsonNodeToValue(JsonNode node) {
+
+        Object value = node;
+        if (node instanceof NullNode) {
+            value = null;
+        } else if (node instanceof TextNode) {
+            value = node.asText();
+        } else if (node instanceof BooleanNode) {
+            value = node.asBoolean();
+        } else if (node instanceof IntNode) {
+            value = node.asInt();
+        } else if (node instanceof FloatNode) {
+            value = (float)((FloatNode)node).asDouble();
+        } else if (node instanceof DoubleNode) {
+            value = (float)((DoubleNode)node).asDouble();
+        } else if (node instanceof ArrayNode) {
+
+            int numItems = node.size();
+            String[] values = new String[numItems];
+            for (int i = 0; i < numItems; i++) {
+                values[i] = node.path(i).asText();
+            }
+
+            value = values;
+        }
+
+        return (value);
+    }
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
+}

src/main/java/org/gitlab4j/api/models/Setting.java

+package org.gitlab4j.api.models;
+
+import org.gitlab4j.api.GitLabApiException;
+import org.gitlab4j.api.utils.JacksonJsonEnumHelper;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * This enum provides constants and value validation for the available GitLab application settings.
+ * See <a href="https://docs.gitlab.com/ce/api/settings.html#list-of-settings-that-can-be-accessed-via-api-calls">
+ * List of settings that can be accessed via API calls</a> for more information.
+ */
+public enum Setting {
+
+    /**
+     * Abuse reports will be sent to this address if it is set. Abuse reports are
+     * always available in the admin area.
+     */
+    ADMIN_NOTIFICATION_EMAIL(String.class),
+
+    /** Where to redirect users after logout. */
+    AFTER_SIGN_OUT_PATH(String.class),
+
+    /** Text shown to the user after signing up */
+    AFTER_SIGN_UP_TEXT(String.class),
+
+    /** required by: akismet_enabled API key for akismet spam protection. */
+    AKISMET_API_KEY(String.class),
+
+    /**
+     * (If enabled, requires: akismet_api_key) Enable or disable akismet spam
+     * protection.
+     */
+    AKISMET_ENABLED(Boolean.class),
+
+    /** (Premium) Set to true to allow group owners to manage LDAP */
+    ALLOW_GROUP_OWNERS_TO_MANAGE_LDAP(Boolean.class),
+
+    /** Allow requests to the local network from hooks and services. */
+    ALLOW_LOCAL_REQUESTS_FROM_HOOKS_AND_SERVICES(Boolean.class),
+
+    /**
+     * By default, we write to the authorized_keys file to support Git over SSH
+     * without additional configuration. GitLab can be optimized to authenticate SSH
+     * keys via the database file. Only disable this if you have configured your
+     * OpenSSH server to use the AuthorizedKeysCommand.
+     */
+    AUTHORIZED_KEYS_ENABLED(Boolean.class),
+
+    /**
+     * Specify a domain to use by default for every project’s Auto Review Apps and
+     * Auto Deploy stages.
+     */
+    AUTO_DEVOPS_DOMAIN(String.class),
+
+    /**
+     * Enable Auto DevOps for projects by default. It will automatically build,
+     * test, and deploy applications based on a predefined CI/CD configuration.
+     */
+    AUTO_DEVOPS_ENABLED(Boolean.class),
+
+    /**
+     * (Premium) Enabling this will make only licensed EE features available to
+     * projects if the project namespace’s plan includes the feature or if the
+     * project is public.
+     */
+    CHECK_NAMESPACE_PLAN(Boolean.class),
+
+    /**
+     * required by: clientside_sentry_enabled Clientside Sentry Data Source Name.
+     */
+    CLIENTSIDE_SENTRY_DSN(String.class),
+
+    /**
+     * (If enabled, requires: clientside_sentry_dsn) Enable Sentry error reporting
+     * for the client side.
+     */
+    CLIENTSIDE_SENTRY_ENABLED(Boolean.class),
+
+    /** Container Registry token duration in minutes. */
+    CONTAINER_REGISTRY_TOKEN_EXPIRE_DELAY(Integer.class),
+
+    /** Set the default expiration time for each job’s artifacts. */
+    DEFAULT_ARTIFACTS_EXPIRE_IN(String.class),
+
+    /**
+     * Determine if developers can push to master. Can take: 0 (not protected, both
+     * developers and maintainers can push new commits, force push, or delete the
+     * branch), 1 (partially protected, developers and maintainers can push new
+     * commits, but cannot force push or delete the branch) or 2 (fully protected,
+     * developers cannot push new commits, but maintainers can; no-one can force
+     * push or delete the branch) as a parameter. Default is 2.
+     */
+    DEFAULT_BRANCH_PROTECTION(Integer.class),
+
+    /**
+     * What visibility level new groups receive. Can take private, internal and
+     * public as a parameter. Default is private.
+     */
+    DEFAULT_GROUP_VISIBILITY(String.class),
+
+    /**
+     * What visibility level new projects receive. Can take private, internal and
+     * public as a parameter. Default is private.
+     */
+    DEFAULT_PROJECT_VISIBILITY(String.class),
+
+    /** Project limit per user. Default is 100000. */
+    DEFAULT_PROJECTS_LIMIT(Integer.class),
+
+    /**
+     * What visibility level new snippets receive. Can take private, internal and
+     * public as a parameter. Default is private.
+     */
+    DEFAULT_SNIPPET_VISIBILITY(String.class),
+
+    /** Disabled OAuth sign-in sources. */
+    DISABLED_OAUTH_SIGN_IN_SOURCES(String[].class),
+
+    /**
+     * required by: domain_blacklist_enabled Users with e-mail addresses that match
+     * these domain(s) will NOT be able to sign-up. Wildcards allowed. Use separate
+     * lines for multiple entries. Ex: domain.com, *.domain.com.
+     */
+    DOMAIN_BLACKLIST(String[].class),
+
+    /**
+     * (If enabled, requires: domain_blacklist) Allows blocking sign-ups from emails
+     * from specific domains.
+     */
+    DOMAIN_BLACKLIST_ENABLED(Boolean.class),
+
+    /**
+     * Force people to use only corporate emails for sign-up. Default is null,
+     * meaning there is no restriction.
+     */
+    DOMAIN_WHITELIST(String[].class),
+
+    /**
+     * The minimum allowed bit length of an uploaded DSA key. Default is 0 (no
+     * restriction). -1 disables DSA keys.
+     */
+    DSA_KEY_RESTRICTION(Integer.class),
+
+    /**
+     * The minimum allowed curve size (in bits) of an uploaded ECDSA key. Default is
+     * 0 (no restriction). -1 disables ECDSA keys.
+     */
+    ECDSA_KEY_RESTRICTION(Integer.class),
+
+    /**
+     * The minimum allowed curve size (in bits) of an uploaded ED25519 key. Default
+     * is 0 (no restriction). -1 disables ED25519 keys.
+     */
+    ED25519_KEY_RESTRICTION(Integer.class),
+
+    /** (Premium) Enable the use of AWS hosted Elasticsearch */
+    ELASTICSEARCH_AWS(Boolean.class),
+
+    /** (Premium) AWS IAM access key */
+    ELASTICSEARCH_AWS_ACCESS_KEY(String.class),
+
+    /** (Premium) The AWS region the elasticsearch domain is configured */
+    ELASTICSEARCH_AWS_REGION(String.class),
+
+    /** (Premium) AWS IAM secret access key */
+    ELASTICSEARCH_AWS_SECRET_ACCESS_KEY(String.class),
+
+    /**
+     * (Premium) Use the experimental elasticsearch indexer. More info:
+     * https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer
+     */
+    ELASTICSEARCH_EXPERIMENTAL_INDEXER(Boolean.class),
+
+    /** (Premium) Enable Elasticsearch indexing */
+    ELASTICSEARCH_INDEXING(Boolean.class),
+
+    /** (Premium) Enable Elasticsearch search */
+    ELASTICSEARCH_SEARCH(Boolean.class),
+
+    /**
+     * (Premium) The url to use for connecting to Elasticsearch. Use a
+     * comma-separated list to support cluster (e.g., “http://localhost:9200,
+     * http://localhost:9201"). If your Elasticsearch instance is password
+     * protected, pass the username:password in the URL,
+     */
+    ELASTICSEARCH_URL(String.class),
+
+    /**
+     * (Premium) Additional text added to the bottom of every email for
+     * legal/auditing/compliance reasons
+     */
+    EMAIL_ADDITIONAL_TEXT(String.class),
+
+    /**
+     * Some email servers do not support overriding the email sender name. Enable
+     * this option to include the name of the author of the issue, merge request or
+     * comment in the email body instead.
+     */
+    EMAIL_AUTHOR_IN_BODY(Boolean.class),
+
+    /**
+     * Enabled protocols for Git access. Allowed values are: ssh, http, and nil to
+     * allow both protocols.
+     */
+    ENABLED_GIT_ACCESS_PROTOCOL(String.class),
+
+    /** (If enabled, requires: terms) Enforce application ToS to all users. */
+    ENFORCE_TERMS(Boolean.class),
+
+    /**
+     * (Premium) (If enabled, requires: external_auth_client_key) The certificate to
+     * use to authenticate with the external authorization service
+     */
+    EXTERNAL_AUTH_CLIENT_CERT(String.class),
+
+    /**
+     * required by: external_auth_client_cert (Premium) Private key for the
+     * certificate when authentication is required for the external authorization
+     * service, this is encrypted when stored
+     */
+    EXTERNAL_AUTH_CLIENT_KEY(String.class),
+
+    /**
+     * (Premium) Passphrase to use for the private key when authenticating with the
+     * external service this is encrypted when stored
+     */
+    EXTERNAL_AUTH_CLIENT_KEY_PASS(String.class),
+
+    /**
+     * required by: external_authorization_service_enabled (Premium) The default
+     * classification label to use when requesting authorization and no
+     * classification label has been specified on the project
+     */
+    EXTERNAL_AUTHORIZATION_SERVICE_DEFAULT_LABEL(String.class),
+
+    /**
+     * (Premium) (If enabled, requires:
+     * external_authorization_service_default_label,
+     * external_authorization_service_timeout and external_authorization_service_url
+     * ) Enable using an external authorization service for accessing projects
+     */
+    EXTERNAL_AUTHORIZATION_SERVICE_ENABLED(Boolean.class),
+
+    /**
+     * required by: external_authorization_service_enabled (Premium) The timeout
+     * after which an authorization request is aborted, in seconds. When a request
+     * times out, access is denied to the user. (min: 0.001, max: 10, step: 0.001)
+     */
+    EXTERNAL_AUTHORIZATION_SERVICE_TIMEOUT(Float.class),
+
+    /**
+     * required by: external_authorization_service_enabled (Premium) URL to which
+     * authorization requests will be directed
+     */
+    EXTERNAL_AUTHORIZATION_SERVICE_URL(String.class),
+
+    /** (Premium) The ID of a project to load custom file templates from */
+    FILE_TEMPLATE_PROJECT_ID(Integer.class),
+
+    /**
+     * Start day of the week for calendar views and date pickers. Valid values are 0
+     * (default) for Sunday, 1 for Monday, and 6 for Saturday.
+     */
+    FIRST_DAY_OF_WEEK(Integer.class),
+
+    /**
+     * (Premium) Comma-separated list of IPs and CIDRs of allowed secondary nodes.
+     * For example, 1.1.1.1, 2.2.2.0/24.
+     */
+    GEO_NODE_ALLOWED_IPS(String.class),
+
+    /**
+     * (Premium) The amount of seconds after which a request to get a secondary node
+     * status will time out.
+     */
+    GEO_STATUS_TIMEOUT(Integer.class),
+
+    /**
+     * Default Gitaly timeout, in seconds. This timeout is not enforced for git
+     * fetch/push operations or Sidekiq jobs. Set to 0 to disable timeouts.
+     */
+    GITALY_TIMEOUT_DEFAULT(Integer.class),
+
+    /**
+     * Gitaly fast operation timeout, in seconds. Some Gitaly operations are
+     * expected to be fast. If they exceed this threshold, there may be a problem
+     * with a storage shard and ‘failing fast’ can help maintain the stability of
+     * the GitLab instance. Set to 0 to disable timeouts.
+     */
+    GITALY_TIMEOUT_FAST(Integer.class),
+
+    /**
+     * Medium Gitaly timeout, in seconds. This should be a value between the Fast
+     * and the Default timeout. Set to 0 to disable timeouts.
+     */
+    GITALY_TIMEOUT_MEDIUM(Integer.class),
+
+    /** Enable Gravatar. */
+    GRAVATAR_ENABLED(Boolean.class),
+
+    /**
+     * Create new projects using hashed storage paths: Enable immutable, hash-based
+     * paths and repository names to store repositories on disk. This prevents
+     * repositories from having to be moved or renamed when the Project URL changes
+     * and may improve disk I/O performance. (EXPERIMENTAL)
+     */
+    HASHED_STORAGE_ENABLED(Boolean.class),
+
+    /** Hide marketing-related entries from help. */
+    HELP_PAGE_HIDE_COMMERCIAL_CONTENT(Boolean.class),
+
+    /** Alternate support URL for help page. */
+    HELP_PAGE_SUPPORT_URL(String.class),
+
+    /** Custom text displayed on the help page. */
+    HELP_PAGE_TEXT(String.class),
+
+    /** (Premium) GitLab server administrator information */
+    HELP_TEXT(String.class),
+
+    /** Do not display offers from third parties within GitLab. */
+    HIDE_THIRD_PARTY_OFFERS(Boolean.class),
+
+    /** Redirect to this URL when not logged in. */
+    HOME_PAGE_URL(String.class),
+
+    /** required by: housekeeping_enabled Enable Git pack file bitmap creation. */
+    HOUSEKEEPING_BITMAPS_ENABLED(Boolean.class),
+
+    /**
+     * (If enabled, requires: housekeeping_bitmaps_enabled,
+     * housekeeping_full_repack_period, housekeeping_gc_period, and
+     * housekeeping_incremental_repack_period) Enable or disable git housekeeping.
+     */
+    HOUSEKEEPING_ENABLED(Boolean.class),
+
+    /**
+     * required by: housekeeping_enabled Number of Git pushes after which an
+     * incremental git repack is run.
+     */
+    HOUSEKEEPING_FULL_REPACK_PERIOD(Integer.class),
+
+    /**
+     * required by: housekeeping_enabled Number of Git pushes after which git gc is
+     * run.
+     */
+    HOUSEKEEPING_GC_PERIOD(Integer.class),
+
+    /**
+     * required by: housekeeping_enabled Number of Git pushes after which an
+     * incremental git repack is run.
+     */
+    HOUSEKEEPING_INCREMENTAL_REPACK_PERIOD(Integer.class),
+
+    /** Enable HTML emails. */
+    HTML_EMAILS_ENABLED(Boolean.class),
+
+    /**
+     * Sources to allow project import from, possible values: github, bitbucket,
+     * gitlab, google_code, fogbugz, git, and gitlab_project.
+     */
+    IMPORT_SOURCES(String[].class),
+
+    /** When set to true Instance statistics will only be available to admins. */
+    INSTANCE_STATISTICS_VISIBILITY_PRIVATE(Boolean.class),
+
+    /** Increase this value when any cached markdown should be invalidated. */
+    LOCAL_MARKDOWN_VERSION(Integer.class),
+
+    /** Maximum artifacts size in MB */
+    MAX_ARTIFACTS_SIZE(Integer.class),
+
+    /** Limit attachment size in MB */
+    MAX_ATTACHMENT_SIZE(Integer.class),
+
+    /** Maximum size of pages repositories in MB */
+    MAX_PAGES_SIZE(Integer.class),
+
+    /**
+     * (If enabled, requires: metrics_host, metrics_method_call_threshold,
+     * metrics_packet_size, metrics_pool_size, metrics_port, metrics_sample_interval
+     * and metrics_timeout) Enable influxDB metrics.
+     */
+    METRICS_ENABLED(Boolean.class),
+
+    /** required by: metrics_enabled InfluxDB host. */
+    METRICS_HOST(String.class),
+
+    /**
+     * required by: metrics_enabled A method call is only tracked when it takes
+     * longer than the given amount of milliseconds.
+     */
+    METRICS_METHOD_CALL_THRESHOLD(Integer.class),
+
+    /**
+     * required by: metrics_enabled The amount of datapoints to send in a single UDP
+     * packet.
+     */
+    METRICS_PACKET_SIZE(Integer.class),
+
+    /**
+     * required by: metrics_enabled The amount of InfluxDB connections to keep open.
+     */
+    METRICS_POOL_SIZE(Integer.class),
+
+    /**
+     * required by: metrics_enabled The UDP port to use for connecting to InfluxDB.
+     */
+    METRICS_PORT(Integer.class),
+
+    /** required by: metrics_enabled The sampling interval in seconds. */
+    METRICS_SAMPLE_INTERVAL(Integer.class),
+
+    /**
+     * required by: metrics_enabled The amount of seconds after which InfluxDB will
+     * time out.
+     */
+    METRICS_TIMEOUT(Integer.class),
+
+    /**
+     * Allow mirrors to be set up for projects. If disabled, only admins will be
+     * able to set up mirrors in projects.
+     */
+    MIRROR_AVAILABLE(Boolean.class),
+
+    /**
+     * (Premium) Minimum capacity to be available before scheduling more mirrors
+     * preemptively
+     */
+    MIRROR_CAPACITY_THRESHOLD(Integer.class),
+
+    /**
+     * (Premium) Maximum number of mirrors that can be synchronizing at the same
+     * time.
+     */
+    MIRROR_MAX_CAPACITY(Integer.class),
+
+    /**
+     * (Premium) Maximum time (in minutes) between updates that a mirror can have
+     * when scheduled to synchronize.
+     */
+    MIRROR_MAX_DELAY(Integer.class),
+
+    /**
+     * Require users to prove ownership of custom domains. Domain verification is an
+     * essential security measure for public GitLab sites. Users are required to
+     * demonstrate they control a domain before it is enabled.
+     */
+    PAGES_DOMAIN_VERIFICATION_ENABLED(Boolean.class),
+
+    /**
+     * Enable authentication for Git over HTTP(S) via a GitLab account password.
+     * Default is true.
+     */
+    PASSWORD_AUTHENTICATION_ENABLED_FOR_GIT(Boolean.class),
+
+    /**
+     * Enable authentication for the web interface via a GitLab account password.
+     * Default is true.
+     */
+    PASSWORD_AUTHENTICATION_ENABLED_FOR_WEB(Boolean.class),
+
+    /**
+     * (Deprecated: Use performance_bar_allowed_group_path instead) Path of the
+     * group that is allowed to toggle the performance bar.
+     */
+    PERFORMANCE_BAR_ALLOWED_GROUP_ID(String.class),
+
+    /** Path of the group that is allowed to toggle the performance bar. */
+    PERFORMANCE_BAR_ALLOWED_GROUP_PATH(String.class),
+
+    /**
+     * (Deprecated: Pass performance_bar_allowed_group_path: nil instead) Allow
+     * enabling the performance bar.
+     */
+    PERFORMANCE_BAR_ENABLED(Boolean.class),
+
+    /**
+     * (If enabled, requires: plantuml_url) Enable PlantUML integration. Default is
+     * false.
+     */
+    PLANTUML_ENABLED(Boolean.class), // Decimal
+
+    /** required by: plantuml_enabled The PlantUML instance URL for integration. */
+    PLANTUML_URL(String.class),
+
+    /**
+     * Interval multiplier used by endpoints that perform polling. Set to 0 to disable polling.
+     * The documentation liusts this as a decimal, but it is a String in the JSON.
+     */
+    POLLING_INTERVAL_MULTIPLIER(String.class),
+
+    /** Enable project export. */
+    PROJECT_EXPORT_ENABLED(Boolean.class),
+
+    /** Enable prometheus metrics. */
+    PROMETHEUS_METRICS_ENABLED(Boolean.class),
+
+    /**
+     * (Premium) When enabled, GitLab will run a background job that will produce
+     * pseudonymized CSVs of the GitLab database that will be uploaded to your
+     * configured object storage directory.
+     */
+    PSEUDONYMIZER_ENABLED(Boolean.class),
+
+    /**
+     * (If enabled, requires: recaptcha_private_key and recaptcha_site_key) Enable
+     * recaptcha.
+     */
+    RECAPTCHA_ENABLED(Boolean.class),
+
+    /** required by: recaptcha_enabled Private key for recaptcha. */
+    RECAPTCHA_PRIVATE_KEY(String.class),
+
+    /** required by: recaptcha_enabled Site key for recaptcha. */
+    RECAPTCHA_SITE_KEY(String.class),
+
+    /**
+     * GitLab will periodically run git fsck in all project and wiki repositories to
+     * look for silent disk corruption issues.
+     */
+    REPOSITORY_CHECKS_ENABLED(Boolean.class),
+
+    /** (Premium) Size limit per repository (MB) */
+    REPOSITORY_SIZE_LIMIT(Integer.class),
+
+    /**
+     * A list of names of enabled storage paths, taken from gitlab.yml. New projects
+     * will be created in one of these stores, chosen at random.
+     */
+    REPOSITORY_STORAGES(String[].class),
+
+    /**
+     * (If enabled, requires: two_factor_grace_period) Require all users to set up
+     * Two-factor authentication.
+     */
+    REQUIRE_TWO_FACTOR_AUTHENTICATION(Boolean.class),
+
+    /**
+     * Selected levels cannot be used by non-admin users for groups, projects or
+     * snippets. Can take private, internal and public as a parameter. Default is
+     * null which means there is no restriction.
+     */
+    RESTRICTED_VISIBILITY_LEVELS(String[].class),
+
+    /**
+     * The minimum allowed bit length of an uploaded RSA key. Default is 0 (no
+     * restriction). -1 disables RSA keys.
+     */
+    RSA_KEY_RESTRICTION(Integer.class),
+
+    /** Send confirmation email on sign-up. */
+    SEND_USER_CONFIRMATION_EMAIL(Boolean.class),
+
+    /** required by: sentry_enabled Sentry Data Source Name. */
+    SENTRY_DSN(String.class),
+
+    /**
+     * (If enabled, requires: sentry_dsn) Sentry is an error reporting and logging
+     * tool which is currently not shipped with GitLab, available at
+     * https://sentry.io.
+     */
+    SENTRY_ENABLED(Boolean.class),
+
+    /** Session duration in minutes. GitLab restart is required to apply changes */
+    SESSION_EXPIRE_DELAY(Integer.class),
+
+	/**
+     * (If enabled, requires: shared_runners_text and shared_runners_minutes)
+     * Enable shared runners for new projects.
+     */
+    SHARED_RUNNERS_ENABLED(Boolean.class),
+
+    /**
+     * required by: shared_runners_enabled (Premium) Set the maximum number of
+     * pipeline minutes that a group can use on shared Runners per month.
+     */
+    SHARED_RUNNERS_MINUTES(Integer.class),
+
+    /** required by: shared_runners_enabled Shared runners text. */
+    SHARED_RUNNERS_TEXT(String.class),
+
+    /** Text on the login page. */
+    SIGN_IN_TEXT(String.class),
+
+    /**
+     * (Deprecated: Use password_authentication_enabled_for_web instead) Flag
+     * indicating if password authentication is enabled for the web interface.
+     * Documentation lists this as a String, but it s a Boolean
+     */
+    SIGNIN_ENABLED(Boolean.class),
+
+    /** Enable registration. Default is true. */
+    SIGNUP_ENABLED(Boolean.class),
+
+    /**
+     * (Premium) (If enabled, requires: slack_app_id, slack_app_secret and
+     * slack_app_secret) Enable Slack app.
+     */
+    SLACK_APP_ENABLED(Boolean.class),
+
+    /**
+     * string required by: slack_app_enabled (Premium) The app id of the Slack-app.
+     */
+    SLACK_APP_ID(String.class),
+
+    /** required by: slack_app_enabled (Premium) The app secret of the Slack-app. */
+    SLACK_APP_SECRET(String.class),
+
+    /**
+     * required by: slack_app_enabled (Premium) The verification token of the
+     * Slack-app.
+     */
+    SLACK_APP_VERIFICATION_TOKEN(String.class),
+
+    /**
+     * Maximum time for web terminal websocket connection (in seconds). Set to 0 for
+     * unlimited time.
+     */
+    TERMINAL_MAX_SESSION_TIME(Integer.class),
+
+    /**
+     * required by: enforce_terms (Required by: enforce_terms) Markdown content for
+     * the ToS.
+     */
+    TERMS(String.class),
+
+    /**
+     * (If enabled, requires: throttle_authenticated_api_period_in_seconds and
+     * throttle_authenticated_api_requests_per_period) Enable authenticated API
+     * request rate limit. Helps reduce request volume (e.g. from crawlers or
+     * abusive bots).
+     */
+    THROTTLE_AUTHENTICATED_API_ENABLED(Boolean.class),
+
+    /**
+     * required by: throttle_authenticated_api_enabled Rate limit period in seconds.
+     */
+    THROTTLE_AUTHENTICATED_API_PERIOD_IN_SECONDS(Integer.class),
+
+    /**
+     * required by: throttle_authenticated_api_enabled Max requests per period per
+     * user.
+     */
+    THROTTLE_AUTHENTICATED_API_REQUESTS_PER_PERIOD(Integer.class),
+
+    /**
+     * (If enabled, requires: throttle_authenticated_web_period_in_seconds and
+     * throttle_authenticated_web_requests_per_period) Enable authenticated web
+     * request rate limit. Helps reduce request volume (e.g. from crawlers or
+     * abusive bots).
+     */
+    THROTTLE_AUTHENTICATED_WEB_ENABLED(Boolean.class),
+
+    /**
+     * required by: throttle_authenticated_web_enabled Rate limit period in seconds.
+     */
+    THROTTLE_AUTHENTICATED_WEB_PERIOD_IN_SECONDS(Integer.class),
+
+    /**
+     * required by: throttle_authenticated_web_enabled Max requests per period per
+     * user.
+     */
+    THROTTLE_AUTHENTICATED_WEB_REQUESTS_PER_PERIOD(Integer.class),
+
+    /**
+     * (If enabled, requires: throttle_unauthenticated_period_in_seconds and
+     * throttle_unauthenticated_requests_per_period) Enable unauthenticated request
+     * rate limit. Helps reduce request volume (e.g. from crawlers or abusive bots).
+     */
+    THROTTLE_UNAUTHENTICATED_ENABLED(Boolean.class),
+
+    /**
+     * required by: throttle_unauthenticated_enabled Rate limit period in seconds.
+     */
+    THROTTLE_UNAUTHENTICATED_PERIOD_IN_SECONDS(Integer.class),
+
+    /**
+     * required by: throttle_unauthenticated_enabled Max requests per period per IP.
+     */
+    THROTTLE_UNAUTHENTICATED_REQUESTS_PER_PERIOD(Integer.class),
+
+    /**
+     * required by: require_two_factor_authentication Amount of time (in hours) that
+     * users are allowed to skip forced configuration of two-factor authentication.
+     */
+    TWO_FACTOR_GRACE_PERIOD(Integer.class),
+
+    /**
+     * (If enabled, requires: unique_ips_limit_per_user and
+     * unique_ips_limit_time_window) Limit sign in from multiple ips.
+     */
+    UNIQUE_IPS_LIMIT_ENABLED(Boolean.class),
+
+    /**
+     * integer required by: unique_ips_limit_enabled Maximum number of ips per user.
+     */
+    UNIQUE_IPS_LIMIT_PER_USER(Integer.class),
+
+    /**
+     * required by: unique_ips_limit_enabled How many seconds an IP will be counted
+     * towards the limit.
+     */
+    UNIQUE_IPS_LIMIT_TIME_WINDOW(Integer.class),
+
+    /** Every week GitLab will report license usage back to GitLab, Inc. */
+    USAGE_PING_ENABLED(Boolean.class),
+
+    /** Newly registered users will be external by default. */
+    USER_DEFAULT_EXTERNAL(Boolean.class),
+
+    /**
+     * Allow users to register any application to use GitLab as an OAuth provider.
+     */
+    USER_OAUTH_APPLICATIONS(Boolean.class),
+
+    /**
+     * When set to false disable the “You won’t be able to pull or push project code
+     * via SSH” warning shown to users with no uploaded SSH key.
+     */
+    USER_SHOW_ADD_SSH_KEY_MESSAGE(Boolean.class),
+
+    /** Let GitLab inform you when an update is available. */
+    VERSION_CHECK_ENABLED(Boolean.class),
+
+	/* The following settings are undocumented, but are returned from the server */
+    ARCHIVE_BUILDS_IN_HUMAN_READABLE(Boolean.class),
+    DEFAULT_PROJECT_CREATION(Integer.class),
+    DOMAIN_BLACKLIST_RAW(String.class),
+    DOMAIN_WHITELIST_RAW(String.class),
+    RECEIVE_MAX_INPUT_SIZE(Integer.class),
+    USER_DEFAULT_INTERNAL_REGEX(String.class),
+    WEB_IDE_CLIENTSIDE_PREVIEW_ENABLED(Boolean.class),
+    DIFF_MAX_PATCH_BYTES(Integer.class),
+    COMMIT_EMAIL_HOSTNAME(String.class),
+    PROTECTED_CI_VARIABLES(Boolean.class),
+    PASSWORD_AUTHENTICATION_ENABLED(Boolean.class);
+
+    private static JacksonJsonEnumHelper<Setting> enumHelper = new JacksonJsonEnumHelper<>(Setting.class);
+
+    private Class<?> type;
+    private Setting(Class<?> type) {
+        this.type = type;
+    }
+
+    public final Class<?> getType() {
+        return (type);
+    }
+
+    @JsonCreator
+    public static Setting forValue(String value) {
+        return enumHelper.forValue(value);
+    }
+
+    @JsonValue
+    public String toValue() {
+        return (enumHelper.toString(this));
+    }
+
+    @Override
+    public String toString() {
+        return (enumHelper.toString(this));
+    }
+
+    /**
+     * Returns true if the provided value is of the correct type specified by this ApplicationSetting enum,
+     * otherwise returns false.
+     *
+     * @param value the value to validate
+     * @return true if the value is of the correct type or null
+     */
+    public boolean isValid(Object value) {
+        return (value == null || value.getClass() == type);
+    }
+
+    /**
+     * Validates the provided value against the data type of this ApplicationSetting enum.
+     * Will throw a GitLabApiException if the value is not of the correct type.
+     *
+     * @param value the value to validate
+     * @throws GitLabApiException if the provided value is not a valid type for the ApplicationSetting
+     */
+    public final void validate(Object value) throws GitLabApiException {
+
+        if (isValid(value)) {
+            return;
+        }
+
+        String errorMsg = String.format("'%s' value is of incorrect type, is %s, should be %s",
+                toValue(), value.getClass().getSimpleName(), getType().getSimpleName());
+        throw new GitLabApiException(errorMsg);
+    }
+}

src/test/java/org/gitlab4j/api/TestApplicationSettingsApi.java

+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Greg Messner <greg@messners.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package org.gitlab4j.api;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assume.assumeTrue;
+
+import static org.gitlab4j.api.models.Setting.LOCAL_MARKDOWN_VERSION;
+import org.gitlab4j.api.models.ApplicationSettings;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+/**
+ * In order for these tests to run you must set the following properties in test-gitlab4j.properties
+ * <p>
+ * TEST_HOST_URL
+ * TEST_PRIVATE_TOKEN
+ * <p>
+ * If any of the above are NULL, all tests in this class will be skipped.
+ */
+@Category(IntegrationTest.class)
+public class TestApplicationSettingsApi extends AbstractIntegrationTest {
+
+    private static GitLabApi gitLabApi;
+    private static Object savedLocalMarkdownVersion;
+    private static boolean fetchedApplicationSettings;
+
+    public TestApplicationSettingsApi() {
+        super();
+    }
+
+    @BeforeClass
+    public static void setup() {
+        // Must setup the connection to the GitLab test server
+        gitLabApi = baseTestSetup();
+
+        if (gitLabApi != null) {
+            try {
+                ApplicationSettings appSettings = gitLabApi.getApplicationSettingsApi().getApplicationSettings();
+                savedLocalMarkdownVersion = appSettings.getSetting(LOCAL_MARKDOWN_VERSION);
+                fetchedApplicationSettings = true;
+            } catch (Exception ignore) {}
+        }
+    }
+
+    @AfterClass
+    public static void teardown() {
+
+        if (fetchedApplicationSettings) {
+            try {
+                gitLabApi.getApplicationSettingsApi().updateApplicationSetting(
+                        LOCAL_MARKDOWN_VERSION, savedLocalMarkdownVersion);
+            } catch (Exception ignore) {}
+        }
+    }
+
+    @Before
+    public void beforeMethod() {
+        assumeTrue(fetchedApplicationSettings);
+    }
+
+    @Test
+    public void testGetApplicationSettings() throws GitLabApiException {
+        ApplicationSettings appSettings = gitLabApi.getApplicationSettingsApi().getApplicationSettings();
+        assertNotNull(appSettings);
+    }
+
+    @Test
+    public void testUpdateApplicationSetting() throws GitLabApiException {
+
+        int newValue = (savedLocalMarkdownVersion != null ? ((Integer)savedLocalMarkdownVersion).intValue() + 1234 : 1234);
+        ApplicationSettings appSettings = gitLabApi.getApplicationSettingsApi().updateApplicationSetting(LOCAL_MARKDOWN_VERSION, newValue);
+        assertNotNull(appSettings);
+
+        Object updatedLocalMarkdownVersion = appSettings.getSetting(LOCAL_MARKDOWN_VERSION);
+        assertEquals(newValue, updatedLocalMarkdownVersion);
+
+        appSettings = gitLabApi.getApplicationSettingsApi().updateApplicationSetting(LOCAL_MARKDOWN_VERSION, savedLocalMarkdownVersion);
+        updatedLocalMarkdownVersion = appSettings.getSetting(LOCAL_MARKDOWN_VERSION);
+        assertEquals(savedLocalMarkdownVersion, updatedLocalMarkdownVersion);
+    }
+
+    @Test
+    public void testUpdateApplicationSettings() throws GitLabApiException {
+
+        // Arrange
+        int newValue = (savedLocalMarkdownVersion != null ? ((Integer)savedLocalMarkdownVersion).intValue() + 123 : 123);
+        ApplicationSettings appSettings = new ApplicationSettings();
+        appSettings.addSetting(LOCAL_MARKDOWN_VERSION, newValue);
+
+        // Act
+        ApplicationSettings updatedAppSettings = gitLabApi.getApplicationSettingsApi().updateApplicationSettings(appSettings);
+
+        // Assert
+        assertNotNull(updatedAppSettings);
+        Object updatedLocalMarkdownVersion = updatedAppSettings.getSetting(LOCAL_MARKDOWN_VERSION);
+        assertEquals(newValue, updatedLocalMarkdownVersion);
+
+        // Arrange
+        appSettings = new ApplicationSettings();
+        appSettings.addSetting(LOCAL_MARKDOWN_VERSION, savedLocalMarkdownVersion);
+
+        // Act
+        updatedAppSettings = gitLabApi.getApplicationSettingsApi().updateApplicationSettings(appSettings);
+
+        // Assert
+        updatedLocalMarkdownVersion = updatedAppSettings.getSetting(LOCAL_MARKDOWN_VERSION);
+        assertEquals(savedLocalMarkdownVersion, updatedLocalMarkdownVersion);
+    }
+}