Re: NullPointerExceptions in v3.6.0

Andy Seaborne Mon, 05 Mar 2018 08:31:56 -0800


On 02/03/18 18:02, Chris Wood wrote:

Hi Andy,

I've answered one question, but got another...

Your comment "What is more, I can't line the stacktrace line numbers up
with the code.  Jena 3.0.1 lines up better" made me sheepishly realise that
my tdbquery path was pointing to an old version of Jena I had locally
(although this was actually v3.3.0). I changed tdbquery to use v3.6.0 and
it worked! But, it struck me that I'd worked on some other code recently
where I'd compiled with 3.6.0 but tested with tdbquery 3.3.0 and hadn't
seen errors - so I did some basic tests.

Even with a mix of versions, I could not reproduce the NPE. The DBformat has not changed and ont at RDF 1.1 / Jena 3.0 was a reload needed.

I've found that reading in a URL directly into a model doesn't result in
this error; i.e. using my previous workflow but using this version of
jena_test.java


import org.apache.jena.query.Dataset;
import org.apache.jena.query.ReadWrite;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.tdb.TDBFactory;

public class jena_test {
public static void main(String args[])
{
Dataset dataset = TDBFactory.createDataset("my_dataset");
Model model = dataset.getDefaultModel();
dataset.begin(ReadWrite.WRITE);

try{
model.add(ModelFactory.createDefaultModel().read("
https://www.w3.org/TR/REC-rdf-syntax/example14.nt";, "N-TRIPLE"));
dataset.commit();
} finally {
dataset.close();
}
}
}


In your first example theer are

 ModelFactory.createDefaultModel().createResource("person:1")
 ModelFactory.createDefaultModel().createResource("Chris")

which are dubious URIs (the first is the "person:" URI schema, not anamespace of person, the second is a relative URI).



https://www.w3.org/TR/REC-rdf-syntax/example14.nt

is all good URIs.

    Andy



with the same pom version but tdbquery v3.3.0

C:\Users\chris\jena_test>tdbquery --version
Jena:       VERSION: 3.3.0
Jena:       BUILD_DATE: 2017-05-02T17:38:25+0000
ARQ:        VERSION: 3.3.0
ARQ:        BUILD_DATE: 2017-05-02T17:38:25+0000
RIOT:       VERSION: 3.3.0
RIOT:       BUILD_DATE: 2017-05-02T17:38:25+0000
TDB:        VERSION: 3.3.0
TDB:        BUILD_DATE: 2017-05-02T17:38:25+0000



results in

C:\Users\chris\jena_test >tdbquery --loc="my_dataset" "SELECT (count(*) as
?t) where {?a ?b ?c . }"
-----
| t |
=====
| 2 |
-----

As expected.

I recognise that using different versions of jena for compiling and for
tdbquery is almost certainly not supported (even if not implicitly), but
perhaps raising awareness from the troubles I've had this week might help
someone else!

Cheers
Chris





On 2 March 2018 at 13:38, Andy Seaborne <[email protected]> wrote:

Hi Chris,

I am on Linux, with Apache Maven 3.5.2, java openjdk version "1.8.0_151".

It works for me.

What is more, I can't line the stacktrace line numbers up with the code.
Jena 3.0.1 lines up better on

JournalControl.recoverSegment(JournalControl.java:185)

because that is a call to "replay"


I ran the maven compiled version with

  java -cp target/classes:target/tdb_generator_resources/\* jena_test

and then

java -cp /home/afs/jlib/apache-jena-3.6.0/lib/\* tdb.tdbquery
--loc=my_dataset 'SELECT (count(*) as ?t) where {?a ?b ?c . }'

"tdbquery --version" ==>

Jena:       VERSION: 3.7.0-SNAPSHOT
Jena:       BUILD_DATE: 2018-02-27T22:54:52+0000
ARQ:        VERSION: 3.7.0-SNAPSHOT
ARQ:        BUILD_DATE: 2018-02-27T22:54:52+0000
RIOT:       VERSION: 3.7.0-SNAPSHOT
RIOT:       BUILD_DATE: 2018-02-27T22:54:52+0000
TDB:        VERSION: ${project.version}
TDB:        BUILD_DATE: ${build.time.xsd}

(the TDB bit is old junk in 3.6.0 - ignore it)

On 01/03/18 18:05, Chris Wood wrote:

java -jar .\target\jena_test.jar


The shade plugin wasn't configured to run, nor was it set to call the
right main class.

When I change the configuration, I also ran:

java -jar target/jena_test.jar

In all cases I got:

-----
| t |
=====
| 1 |
-----

So it's still a mystery to me, I'm afraid.

         Andy

   <plugin>
     <groupId>org.apache.maven.plugins</groupId>
     <artifactId>maven-shade-plugin</artifactId>
     <version>3.1.0</version>
     <executions>
       <execution>
         <phase>package</phase>
         <goals>
           <goal>shade</goal>
         </goals>
       </execution>
     </executions>
     <configuration>
       <shadedArtifactAttached>false</shadedArtifactAttached>
       <transformers>
         <mainClass>jena_test</mainClass>

         ....

Re: NullPointerExceptions in v3.6.0

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