[jira] [Created] (JENA-1428) NPE in Query Builder

["Claude Warren (JIRA)" <ji...@apache.org>]

Claude Warren created JENA-1428:
-----------------------------------

             Summary: NPE in Query Builder
                 Key: JENA-1428
                 URL: https://issues.apache.org/jira/browse/JENA-1428
             Project: Apache Jena
          Issue Type: Bug
          Components: QueryBuilder
    Affects Versions: Jena 3.4.0
            Reporter: Claude Warren
            Assignee: Claude Warren


As reported by Chris Dollin on users mailing list:

I was experimenting with the query builder and hit a problem
when I was attempting to construct an Expr. This example:

package com.epimorphics.scratch;

import org.apache.jena.arq.querybuilder.ConstructBuilder;
import org.apache.jena.sparql.expr.E_GreaterThan;
import org.apache.jena.sparql.expr.Expr;
import org.apache.jena.sparql.expr.ExprVar;
import org.apache.jena.sparql.expr.nodevalue.NodeValueInteger;
import org.junit.Test;

public class Example {

    @Test public void tryBuilding() {
        ConstructBuilder cb = new ConstructBuilder();

        Expr x = new NodeValueInteger(1);
        Expr y = new ExprVar("y");
        Expr e = new E_GreaterThan(x, y);
        cb.addFilter(e);
        System.err.println(cb.buildString());
    }
}

when run fails with a null pointer exception:

java.lang.NullPointerException
    at org.apache.jena.arq.querybuilder.rewriters.
AbstractRewriter.changeNode(AbstractRewriter.java:126)
    at org.apache.jena.arq.querybuilder.rewriters.NodeValueRewriter.visit(
NodeValueRewriter.java:64)
    at org.apache.jena.sparql.expr.nodevalue.NodeValueInteger.
visit(NodeValueInteger.java:78)
    at org.apache.jena.arq.querybuilder.rewriters.ExprRewriter.visit(
ExprRewriter.java:127)
    at org.apache.jena.sparql.expr.NodeValue.visit(NodeValue.java:1205)
    at org.apache.jena.arq.querybuilder.rewriters.ExprRewriter.visit(
ExprRewriter.java:65)
    at org.apache.jena.sparql.expr.ExprFunction2.visit(
ExprFunction2.java:109)
    at org.apache.jena.arq.querybuilder.rewriters.ElementRewriter.visit(
ElementRewriter.java:70)
    at org.apache.jena.sparql.syntax.ElementFilter.visit(
ElementFilter.java:35)
    at org.apache.jena.arq.querybuilder.rewriters.ElementRewriter.visit(
ElementRewriter.java:141)
    at org.apache.jena.sparql.syntax.ElementGroup.visit(
ElementGroup.java:120)
    at org.apache.jena.arq.querybuilder.handlers.WhereHandler.addAll(
WhereHandler.java:81)
    at org.apache.jena.arq.querybuilder.handlers.HandlerBlock.addAll(
HandlerBlock.java:218)
    at org.apache.jena.arq.querybuilder.handlers.HandlerBlock.addAll(
HandlerBlock.java:245)
    at org.apache.jena.arq.querybuilder.AbstractQueryBuilder.build(
AbstractQueryBuilder.java:555)
    at org.apache.jena.arq.querybuilder.AbstractQueryBuilder.buildString(
AbstractQueryBuilder.java:522)
    at com.epimorphics.scratch.Example.tryBuilding(Example.java:20)
    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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(
FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(
ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(
FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.
evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(
BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(
BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(
JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.
startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(
JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(
JUnitStarter.java:70)

Replacing the addFilter line with

    cb.addFilter("1 > ?y");

does not fail, terminating with the expected print-out
of a construct query

   CONSTRUCT
    {
    }
  WHERE
    { FILTER ( 1 > ?y )}

I tried poking around with the debugger but couldn't see anyhting
obvious. However, /sometimes/ stepping through the code
results in it working and sometimes not, presumably depending
on exactly when I give up through-stepping.

Am I doing anything obviously wrong (like misunderstanding
how to use the Expr functionality) or should I file a JIRA?
This is Jena 3.4.0.



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