Gremlin Server now can start from ArcadeDB JVM as a plugin

gremlin/pom.xml

@@ -32,11 +32,6 @@
     <artifactId>arcadedb-gremlin</artifactId>
     <packaging>jar</packaging>
 
-    <properties>
-        <gremlin.version>3.5.1</gremlin.version>
-        <junit5.version>5.8.1</junit5.version>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>com.arcadedb</groupId>
@@ -73,7 +68,7 @@
         <dependency>
             <groupId>org.junit.vintage</groupId>
             <artifactId>junit-vintage-engine</artifactId>
-            <version>${junit5.version}</version>
+            <version>${junit.jupiter.version}</version>
             <scope>test</scope>
         </dependency>
     </dependencies>

pom.xml

@@ -48,6 +48,7 @@
         <exclude.tests></exclude.tests>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
+        <gremlin.version>3.5.1</gremlin.version>
         <docker.plugin.version>1.2.2</docker.plugin.version>
         <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
         <jacoco-maven-plugin.version>0.8.7</jacoco-maven-plugin.version>

server/pom.xml

@@ -86,6 +86,11 @@
             <version>${project.parent.version}</version>
             <scope>compile</scope>
         </dependency>
+        <dependency>
+            <groupId>org.apache.tinkerpop</groupId>
+            <artifactId>gremlin-server</artifactId>
+            <version>${gremlin.version}</version>
+        </dependency>
         <dependency>
             <groupId>io.undertow</groupId>
             <artifactId>undertow-core</artifactId>

server/src/main/java/com/arcadedb/server/gremlin/GremlinServerPlugin.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright © 2021-present Arcade Data Ltd (info@arcadedata.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.arcadedb.server.gremlin;
+
+import com.arcadedb.ContextConfiguration;
+import com.arcadedb.log.LogManager;
+import com.arcadedb.server.ArcadeDBServer;
+import com.arcadedb.server.ServerException;
+import com.arcadedb.server.ServerPlugin;
+import com.arcadedb.server.http.HttpServer;
+import io.undertow.server.handlers.PathHandler;
+import org.apache.tinkerpop.gremlin.server.GremlinServer;
+import org.apache.tinkerpop.gremlin.server.Settings;
+
+import java.io.*;
+import java.lang.reflect.*;
+import java.util.logging.*;
+
+public class GremlinServerPlugin implements ServerPlugin {
+  private static final String               CONFIG_GREMLIN_SERVER_YAML = "/config/gremlin-server.yaml";
+  private              ArcadeDBServer       server;
+  private              ContextConfiguration configuration;
+  private              GremlinServer        gremlinServer;
+
+  @Override
+  public void configure(final ArcadeDBServer arcadeDBServer, final ContextConfiguration configuration) {
+    this.server = arcadeDBServer;
+    this.configuration = configuration;
+  }
+
+  @Override
+  public void startService() {
+    Settings settings = null;
+    final File confFile = new File(server.getRootPath() + CONFIG_GREMLIN_SERVER_YAML);
+    if (confFile.exists()) {
+      try (FileInputStream is = new FileInputStream(confFile.getAbsolutePath())) {
+        settings = Settings.read(is);
+      } catch (Exception e) {
+        LogManager.instance()
+            .log(this, Level.INFO, "Error on loading Gremlin Server configuration file '%s'. Using default configuration", null, CONFIG_GREMLIN_SERVER_YAML);
+      }
+    } else
+      LogManager.instance()
+          .log(this, Level.INFO, "Cannot find Gremlin Server configuration file '%s'. Using default configuration", null, CONFIG_GREMLIN_SERVER_YAML);
+
+    if (settings == null)
+      // DEFAULT CONFIGURATION
+      settings = new Settings();
+
+    for (String key : configuration.getContextKeys()) {
+      if (key.startsWith("gremlin.")) {
+        final Object value = configuration.getValue(key, null);
+        final String gremlinConfigKey = key.substring("gremlin.".length());
+
+        try {
+          final Field field = settings.getClass().getField(gremlinConfigKey);
+          field.set(settings, value);
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+          // IGNORE IT
+        }
+      }
+    }
+
+    gremlinServer = new GremlinServer(settings);
+    try {
+      gremlinServer.start();
+    } catch (Exception e) {
+      throw new ServerException("Error on starting GremlinServer plugin", e);
+    }
+  }
+
+  @Override
+  public void stopService() {
+    if (gremlinServer != null)
+      gremlinServer.stop();
+  }
+
+  @Override
+  public void registerAPI(HttpServer httpServer, final PathHandler routes) {
+  }
+}