Adds support for creating graph variables collection if not present

Author: arcanefoam

src/main/java/com/arangodb/tinkerpop/gremlin/structure/ArangoDBGraph.java

@@ -598,10 +598,25 @@ public ArangoDBGraph(Configuration configuration) {
 
         if (graph.exists()) {
             ArangoDBUtil.checkGraphForErrors(prefVCols, prefECols, edgeDefinitions, graph, options);
-            ArangoDBGraphVariables iter = client.getGraphVariables();
-            if (iter == null) {
-            	throw new ArangoDBGraphException("Existing graph does not have a Variables collection");
-            }
+            ArangoDBGraphVariables variables = null;
+            try {
+				variables = client.getGraphVariables();
+			} catch (NullPointerException ex) {
+				logger.warn("Existing graph missing Graph Variables collection ({}), will attempt to create one.", GRAPH_VARIABLES_COLLECTION);
+			}
+            if (variables == null) {
+				variables = new ArangoDBGraphVariables(name, GRAPH_VARIABLES_COLLECTION, this);
+				try {
+					client.insertGraphVariables(variables);
+				} catch (ArangoDBGraphException ex) {
+					throw new ArangoDBGraphException(
+							String.format(
+									"Unable to add graph variables collection (%s) to existing graph. %s",
+									ex.getMessage(),
+									GRAPH_VARIABLES_COLLECTION)
+							, ex);
+				}
+			}
         }
         else {
         	graph = client.createGraph(name, edgeDefinitions, options);

src/main/java/com/arangodb/tinkerpop/gremlin/utils/ArangoDBConfigurationBuilder.java

@@ -59,7 +59,6 @@ public class ArangoDBConfigurationBuilder {
 	private static final String PROPERTY_KEY_ACQUIRE_HOST_LIST = "arangodb.acquireHostList";
 	private static final String PROPERTY_KEY_LOAD_BALANCING_STRATEGY = "arangodb.loadBalancingStrategy";
 	private static final String PROPERTY_KEY_PROTOCOL = "arangodb.protocol";
-	private static final String PROPERTY_KEY_SHOULD_PREFIX_COLLECTION_NAMES = "arangodb.shouldPrefixCollectionNames";
 
 	/** The db name. */
 	private String dbName = "tinkerpop";
@@ -195,7 +194,7 @@ public BaseConfiguration build() {
 			config.addProperty(fullPropertyKey(PROPERTY_KEY_HOSTS), hosts.stream().collect(Collectors.joining(",")));
 		}
 		if(shouldPrefixCollectionNames != null){
-			config.addProperty(fullPropertyKey(PROPERTY_KEY_SHOULD_PREFIX_COLLECTION_NAMES), shouldPrefixCollectionNames);
+			config.addProperty(fullPropertyKey(ArangoDBGraph.PROPERTY_KEY_SHOULD_PREFIX_COLLECTION_NAMES), shouldPrefixCollectionNames);
 		}
 
 		config.addProperty(Graph.GRAPH, ArangoDBGraph.class.getName());

src/main/java/com/arangodb/tinkerpop/gremlin/utils/ArangoDBUtil.java

@@ -325,6 +325,7 @@ public static void checkGraphForErrors(
         		throw new ArangoDBGraphException(String.format("The graph has a surplus edge definition %s", edgeDefinitionString(existing)));
         	}
         }
+
 	}
 
 	private static void checkGraphVertexCollections(List<String> verticesCollectionNames, ArangoGraph graph, GraphCreateOptions options) {

src/test/java/com/arangodb/tinkerpop/gremlin/Issue57.java

@@ -0,0 +1,27 @@
+package com.arangodb.tinkerpop.gremlin;
+
+import com.arangodb.tinkerpop.gremlin.structure.ArangoDBGraph;
+import com.arangodb.tinkerpop.gremlin.utils.ArangoDBConfigurationBuilder;
+import org.apache.commons.configuration.Configuration;
+
+import java.io.File;
+
+
+public class Issue57 {
+
+    public static void main(String... args) {
+        ArangoDBConfigurationBuilder builder = new ArangoDBConfigurationBuilder();
+        builder.dataBase("Test02")
+                .graph("Test02Graph01")
+                .arangoUser("gremlin")
+                .arangoPassword("gremlin")
+                .arangoHosts("127.0.0.1:8529")
+                .withEdgeCollection("testedge")
+                .withVertexCollection("testfrom")
+                .withVertexCollection("testto")
+                .shouldPrefixCollectionNamesWithGraphName(false)
+                .configureEdge("testedge", "testfrom", "testto");
+
+        ArangoDBGraph g = ArangoDBGraph.open(builder.build());
+    }
+}

src/test/java/com/arangodb/tinkerpop/gremlin/test.conf

@@ -0,0 +1,11 @@
+gremlin.graph = com.arangodb.tinkerpop.gremlin.structure.ArangoDBGraph
+gremlin.arangodb.conf.graph.db = Test02
+gremlin.arangodb.conf.graph.name = Test02Graph01
+gremlin.arangodb.conf.graph.vertex = testfrom
+gremlin.arangodb.conf.graph.vertex = testto
+gremlin.arangodb.conf.graph.edge = testedge
+gremlin.arangodb.conf.graph.relation = testedge:testfrom->testto
+gremlin.arangodb.conf.graph.shouldPrefixCollectionNames = false
+gremlin.arangodb.conf.arangodb.hosts = 127.0.0.1:8529
+gremlin.arangodb.conf.arangodb.user = xxxx
+gremlin.arangodb.conf.arangodb.password = xxxx