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Date: Sat, 03 Mar 2012 14:49:16 +0100
From: Sebastian Schelter <ssc@apache.org>
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To: giraph-user@incubator.apache.org
Subject: Re: Error in instantiating custom Vertex class via
 InternalVertexRunner.run
References: <F57EEDFE-9E04-4B5B-B825-C6DF45E01B78@deri.org>
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Hi Benjamin,

Does your vertex class have a publicly accessible no-arg constructor?
That's implicitly required because each Vertex class implements Writable.

If you want to use to have a look at your code, you could maybe put it
on github?

Best,
Sebastian

On 02.03.2012 20:51, Benjamin Heitmann wrote:
> Hello, 
> 
> in the last week I started working with Apache Giraph. My goal is to implement a version of the 
> spreading activation algorithm (as described on Wikipedia [1] and in this article [2] ). 
> Using Giraph will hopefully allow scaling for Linked Data/RDF from DBPedia.
> 
> I used the ConnectedComponentsVertex Example (and its UnitTest) as the 
> starting point for my own Vertex, TextInputFormat, TextOutputFormat and UnitTest (and a class for VertexData/State). 
> In addition, I ensured that the ConnectedComponentsVertexTest runs successfully, both from the giraph source tree
> and from my own project. 
> 
> My Vertex class is called SpreadingActivationVertex, and it directly extends BasicVertex, and it has the following <I, V, E, M> signature: 
> public abstract class SpreadingActivationVertex extends
> BasicVertex<IntWritable, SpreadingActivationStateWritable, NullWritable, DoubleWritable>
> As you can see, I need to maintain more then one variable for the state of the vertex, 
> and I need to pass doubles as messages. 
> 
> When I execute my UnitTest, I get the following error: 
> 
> 59820 [Thread-4] WARN  org.apache.hadoop.mapred.LocalJobRunner  - job_local_0001
> java.lang.RuntimeException: java.lang.InstantiationException
> 	at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
> 	at org.apache.giraph.graph.BspUtils.createVertex(BspUtils.java:365)
> 	at ie.deri.uimr.ld_sa.prototyping.giraph.SpreadingActivationTextInputFormat$SpreadingActivationVertexReader.getCurrentVertex(SpreadingActivationTextInputFormat.java:53)
> 	at org.apache.giraph.graph.BspServiceWorker.readVerticesFromInputSplit(BspServiceWorker.java:440)
> 	at org.apache.giraph.graph.BspServiceWorker.loadVerticesFromInputSplit(BspServiceWorker.java:371)
> 	at org.apache.giraph.graph.BspServiceWorker.loadVertices(BspServiceWorker.java:305)
> 	at org.apache.giraph.graph.BspServiceWorker.setup(BspServiceWorker.java:583)
> 	at org.apache.giraph.graph.GraphMapper.setup(GraphMapper.java:474)
> 	at org.apache.giraph.graph.GraphMapper.run(GraphMapper.java:646)
> 	at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:763)
> 	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:369)
> 	at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:210)
> Caused by: java.lang.InstantiationException
> 	at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30)
> 	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
> 	at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:113)
> 	... 11 more
> 
> 
> Using the eclipse debugger, I traced it to these lines of code in Hadoop: 
> 
> org.apache.hadoop.util.ReflectionUtils, line 113 in newInstance():
> 
>     try {
>       Constructor<T> meth = (Constructor<T>) CONSTRUCTOR_CACHE.get(theClass);
>       if (meth == null) {
>         meth = theClass.getDeclaredConstructor(EMPTY_ARRAY);
>         meth.setAccessible(true);
>         CONSTRUCTOR_CACHE.put(theClass, meth);
>       }
>       result = meth.newInstance();    // <<<------------ this is the line causing the error
>     } catch (Exception e) {
>       throw new RuntimeException(e);
>     }
> 
> The constructor cache does not contain my vertex class, however the next lines successfully find the right constructor and put it into "meth". 
> However, the invocation of meth.newInstance() fails with the above error. 
> 
> 
> Did somebody have this error before ? 
> What did I miss ? 
> The class itself is successfully found, so it is not an issue of setting some paths.
> However getting a newInstance seems to fail for some reason. 
> 
> Would it be helpful if I provide the code for my 5 classes somewhere ? If yes, in which way would that be convenient for this mailing list ? 
> 
> 
> 
> [1] https://en.wikipedia.org/wiki/Spreading_activation
> [2] http://linkinghub.elsevier.com/retrieve/pii/0306457387900173
>