NullPointerException when native query with null result

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lotzy

Hi there,

We need to find out the last executed process with a given name so we used this piece of code:

NativeHistoricProcessInstanceQuery haiq = historyService.createNativeHistoricProcessInstanceQuery();
HistoricProcessInstance processNative = haiq.sql("SELECT MAX(id_) AS id FROM act_hi_procinst WHERE business_key_ = '"+processName+"'").singleResult(); ‍‍

and then with the max id we will load the whole HistoricProcessInstanceQuery:

HistoricProcessInstanceQuery hquery = historyService.createHistoricProcessInstanceQuery();
return hquery.processInstanceId(processNative.getId()).singleResult();‍‍

The problem is that when the native query of SELECT MAX() has null result because there is no process executed with the given "processName" name, then throws

java.lang.NullPointerException
   at org.activiti.engine.impl.persistence.entity.HistoricProcessInstanceEntityManager.findHistoricProcessInstanceCountByNativeQuery(HistoricProcessInstanceEntityManager.java:99)

and does not returns null as we would expect.

Do you have a workaround for this problem other than catching the NullPointerException in a try-catch block?

Thank you.

martin_grofcik

Hi.

I have implemented small jUnit test (https://github.com/martin-grofcik/Activiti/commit/b311ba6c8729633c17df1d33ad42288b9ac386ee)
<code>
    @Deployment(resources = {"org/activiti/engine/test/history/oneTaskProcess.bpmn20.xml"})
    public void testNativeHistoricProcessInstanceQuery() {
        NativeHistoricProcessInstanceQuery haiq = historyService.createNativeHistoricProcessInstanceQuery();
        HistoricProcessInstance processNative = haiq.sql("SELECT MAX(id_) AS id FROM act_hi_procinst WHERE business_key_ = 'DOES_NOT_EXIST'").singleResult();
        assertEquals(null, processNative);
    }
</code>

It passes. May be I did something wrong.

Question
Could you create jUnit test for it?

Idea
Can you query DB to get rows count before SELECT MAX(id_) ? (I know it is overhead.)