Tinkerpop console returns nullpointerexception when reading graphml with subgraph - tinkerpop

Question

I'm just getting started with the tinkerpop console and am interested in using it to work with graphml files that have subgraphs. I have gone through the 'Getting Started' and started the other documentation.
While I can import a graphml file without subgraphs, I'm not able to read the file when subgraphs exist. Is this supported? (my search of the site didn't indicate it wasn't unsupported)
gremlin> graph = TinkerGraph.open()
==>tinkergraph[vertices:0 edges:0]
gremlin> graph.io(graphml()).readGraph('data/xsmall0.graphml')
==>null
gremlin> g = graph.traversal()
==>graphtraversalsource[tinkergraph[vertices:3 edges:2], standard]
gremlin> g.V()
==>v[n1]
==>v[n2]
==>v[n3]
gremlin> graph = TinkerGraph.open()
==>tinkergraph[vertices:0 edges:0]
gremlin> graph.io(graphml()).readGraph('data/xsmall2.graphml')
java.lang.NullPointerException
Type ':help' or ':h' for help.
Display stack trace? [yN]y
java.lang.NullPointerException
at org.apache.tinkerpop.gremlin.structure.io.graphml.GraphMLReader.readGraph(GraphMLReader.java:175)
at org.apache.tinkerpop.gremlin.structure.io.graphml.GraphMLIo.readGraph(GraphMLIo.java:92)
at org.apache.tinkerpop.gremlin.structure.io.Io$readGraph.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at groovysh_evaluate.run(groovysh_evaluate:3)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:232)
at org.codehaus.groovy.tools.shell.Interpreter.evaluate(Interpreter.groovy:70)
at org.codehaus.groovy.tools.shell.Groovysh.execute(Groovysh.groovy:191)
at org.apache.tinkerpop.gremlin.console.GremlinGroovysh.super$3$execute(GremlinGroovysh.groovy)
at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:132)
at org.apache.tinkerpop.gremlin.console.GremlinGroovysh.execute(GremlinGroovysh.groovy:72)
at org.codehaus.groovy.tools.shell.Shell.leftShift(Shell.groovy:122)
at org.codehaus.groovy.tools.shell.ShellRunner.work(ShellRunner.groovy:95)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$work(InteractiveShellRunner.groovy)
at sun.reflect.GeneratedMethodAccessor34.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:132)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:152)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.work(InteractiveShellRunner.groovy:124)
at org.codehaus.groovy.tools.shell.ShellRunner.run(ShellRunner.groovy:59)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.super$2$run(InteractiveShellRunner.groovy)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:132)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuper0(ScriptBytecodeAdapter.java:152)
at org.codehaus.groovy.tools.shell.InteractiveShellRunner.run(InteractiveShellRunner.groovy:83)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:232)
at org.apache.tinkerpop.gremlin.console.Console.<init>(Console.groovy:143)
at org.codehaus.groovy.vmplugin.v7.IndyInterface.selectMethod(IndyInterface.java:232)
at org.apache.tinkerpop.gremlin.console.Console.main(Console.groovy:450)
gremlin>
Here is the xsmall2.graphml file that I'm importing (copied from http://kb.yworks.com/article/78/)
<?xml version="1.0" encoding="UTF-8"?>
<graphml>
<graph id="G" edgedefault="directed">
<node id="n0"/>
<node id="n1"/>
<node id="n2">
<graph id="n2::" edgedefault="directed">
<node id="n2::n0"/>
<node id="n2::n1">
<graph id="n2::n1::" edgedefault="directed">
<node id="n2::n1::n0"/>
<node id="n2::n1::n1"/>
<node id="n2::n1::n2"/>
<edge id="e0" source="n2::n1::n1" target="n2::n1::n0"/>
<edge id="e1" source="n2::n1::n2" target="n2::n1::n1"/>
</graph>
</node>
<node id="n2::n2"/>
<edge id="e2" source="n2::n1" target="n2::n0"/>
<edge id="e3" source="n2::n2" target="n2::n1"/>
</graph>
</node>
<edge id="e4" source="n1" target="n0"/>
<edge id="e5" source="n1" target="n2::n1"/>
<edge id="e6" source="n0" target="n2"/>
</graph>
</graphml>

Answer 1

TinkerPop's GraphMLReader doesn't support subgraphs. I suspect that the parser doesn't expect to find a <graph> element embedded in another <graph> element.