Details
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Bug
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Resolution: Done
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Major
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6.1.0.Final
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None
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None
Description
This is an exercise for "group by" words.
Consider the following pattern for realizing a "group by" by means of from/accumulate/count : the goal is to count Messages which starts with preferred keyword, if the count for a keyword is >= 2, then rule should fire.
declare GroupByString groupId : String groups : String[] end rule "init words of my interest" no-loop when then GroupByString grp = new GroupByString(); grp.setGroupId("wordGroup"); grp.setGroups(new String[]{"ciao", "bella"}); insert(grp); end rule "group by word and count if >=2 then " no-loop when $group : GroupByString( groupId == "wordGroup") $word : String() from $group.groups accumulate ( $msg : Message( text str[startsWith] $word ) over window:time( 5m ) ; $list : collectList( $msg ), $count : count( $msg ); $count >= 2 ) then System.out.println("group by " + $word + " count is "+ $count + " list: " + $list); insert(new Integer($count.intValue())); end
However trying to compile the KB with the kie-maven-plugin fails with this NPE and stacktrace (snippet):
java.lang.NullPointerException at org.drools.compiler.rule.builder.dialect.java.JavaAccumulateBuilder.buildExternalFunctionCall(JavaAccumulateBuilder.java:182) at org.drools.compiler.rule.builder.dialect.java.JavaAccumulateBuilder.build(JavaAccumulateBuilder.java:101) at org.drools.compiler.rule.builder.dialect.java.JavaAccumulateBuilder.build(JavaAccumulateBuilder.java:66) at org.drools.compiler.rule.builder.PatternBuilder.build(PatternBuilder.java:320) at org.drools.compiler.rule.builder.PatternBuilder.build(PatternBuilder.java:138) at org.drools.compiler.rule.builder.GroupElementBuilder.build(GroupElementBuilder.java:66) at org.drools.compiler.rule.builder.RuleBuilder.build(RuleBuilder.java:89) at org.drools.compiler.builder.impl.KnowledgeBuilderImpl.addRule(KnowledgeBuilderImpl.java:1652) at org.drools.compiler.builder.impl.KnowledgeBuilderImpl.compileRules(KnowledgeBuilderImpl.java:968)
I've also noticed the following 2 aspects:
1-/ If you use another operator instead of str startsWith, for instance you replace with the contains operators, it does compile the KB successfully. In this scenario would change the exercise to "count Messages which contains the preferred keyword", but it works:
rule "group by word and count if >=2 then " no-loop when $group : GroupByString( groupId == "wordGroup") $word : String() from $group.groups accumulate ( $msg : Message( text contains $word ) over window:time( 5m ) ; $list : collectList( $msg ), $count : count( $msg ); $count >= 2 ) then System.out.println("group by " + $word + " count is "+ $count + " list: " + $list); insert(new Integer($count.intValue())); end
2-/ If you use an hard-coded operand in the str startsWith, it works too. For instance if you hard-code the rule as:
rule "group by word and count if >=2 then " no-loop when accumulate ( $msg : Message( text str[startsWith] "ciao" ) over window:time( 5m ) ; $list : collectList( $msg ), $count : count( $msg ); $count >= 2 ) then insert(new Integer($count.intValue())); end
It does not give NPE at KB build and executes as expected.
For my application it's okay to deal with the first option above, but anyway I thought worthy to report a JIRA. I will attach reproducer. Ciao