Using JanusGraph with Lucene instead of ElasticSearch - elasticsearch

Question

I am trying to use Lucene instead of ElasticSearch (used by default) when configuring JanusGraph. For this I changed the following in janusgraph-cql-es.properties
index.search.backend=lucene
index.search.directory=/data/searchindex
and also commented out
index.search.hostname=127.0.0.1
However the command to start Janusgraph bin/janusgraph.sh -v start gives this error
3718 [main] ERROR org.janusgraph.graphdb.server.JanusGraphServer - JanusGraph Server was unable to start and will now begin shutdown
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor.<init>(ServerGremlinExecutor.java:97)
at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:127)
at org.apache.tinkerpop.gremlin.server.GremlinServer.<init>(GremlinServer.java:90)
at org.janusgraph.graphdb.server.JanusGraphServer.start(JanusGraphServer.java:85)
at org.janusgraph.graphdb.server.JanusGraphServer.main(JanusGraphServer.java:53)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.apache.tinkerpop.gremlin.server.util.ServerGremlinExecutor.<init>(ServerGremlinExecutor.java:86)
... 4 more
Caused by: java.lang.IllegalArgumentException: Could not instantiate implementation: org.janusgraph.diskstorage.lucene.LuceneIndex
at org.janusgraph.util.system.ConfigurationUtil.instantiate(ConfigurationUtil.java:79)
at org.janusgraph.diskstorage.Backend.getImplementationClass(Backend.java:527)
at org.janusgraph.diskstorage.Backend.getIndexes(Backend.java:511)
at org.janusgraph.diskstorage.Backend.<init>(Backend.java:239)
at org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.getBackend(GraphDatabaseConfiguration.java:1355)
at org.janusgraph.graphdb.database.StandardJanusGraph.<init>(StandardJanusGraph.java:184)
at org.janusgraph.core.JanusGraphFactory.lambda$open$0(JanusGraphFactory.java:165)
at org.janusgraph.graphdb.management.JanusGraphManager.openGraph(JanusGraphManager.java:239)
at org.janusgraph.core.JanusGraphFactory.open(JanusGraphFactory.java:165)
at org.janusgraph.core.JanusGraphFactory.open(JanusGraphFactory.java:115)
at org.janusgraph.graphdb.management.JanusGraphManager.lambda$new$0(JanusGraphManager.java:73)
at java.util.LinkedHashMap.forEach(LinkedHashMap.java:684)
at org.janusgraph.graphdb.management.JanusGraphManager.<init>(JanusGraphManager.java:72)
... 9 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.janusgraph.util.system.ConfigurationUtil.instantiate(ConfigurationUtil.java:73)
... 21 more
Caused by: java.lang.NullPointerException
at java.io.File.<init>(File.java:279)
at org.janusgraph.diskstorage.lucene.LuceneIndex.<init>(LuceneIndex.java:185)
... 26 more
What configuration changes need to be done here? Or can Lucene only be used with HBase as storage backend as shown here?