How to handle null exeption

[Artyom]

Hi, need help with persistence:

var pwr = (PwrCounter.historicState(now.toDateMidnight, "rrd4j").state as DecimalType

I got error:

2015-05-02 23:55:03.243 [ERROR] [.o.m.r.i.engine.ExecuteRuleJob] - Error during the execution of rule Counters plus
java.lang.NullPointerException: cannot invoke method public abstract org.openhab.core.types.State org.openhab.core.persistence.HistoricItem.getState() on null

How to handle null exeption?

[Алексей Власов]

if (PwrCounter.historicState(now.toDateMidnight, "rrd4j").state != null) { 

var pwr = (PwrCounter.historicState(now.toDateMidnight, "rrd4j").state as DecimalType

} else {...}

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С уважением,
Алексей А. Власов

[Artyom]

doesnt work

rule "Counters plus"
when
   Time cron "0 * * * * ?"
then

    if (PwrCounter.historicState(now.toDateMidnight, "rrd4j").state != null) {
        var pwr = (PwrCounter.historicState(now.toDateMidnight, "rrd4j").state as DecimalType

    logInfo("PwrCounter.historicState="+ pwr.toString)
    }
end

2015-05-03 23:27:03.737 [ERROR] [.o.m.r.i.engine.ExecuteRuleJob] - Error during the execution of rule Counters plus
java.lang.NullPointerException: null
    at org.openhab.model.script.lib.NumberExtensions.operator_notEquals(NumberExtensions.java:89) ~[na:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_79]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[na:1.7.0_79]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.7.0_79]
......

воскресенье, 3 мая 2015 г., 12:16:22 UTC+3 пользователь Алексей Власов написал: