How to catch errors from GlideEvaluator/GlideScopedEvaluator

onnosteenbergen
Kilo Explorer

‎08-31-2017 05:02 AM

I would like to get/catch errors from evaluated code and store them

Example code:

The example is very short, I did use the GlideEvaluator for this example, although GlideScopedEvaluator has the same issue.

try{
       var result = GlideEvaluator.evaluateString("throw Error('stop');");
       gs.log('Got Result: ' + result);
} catch(err){
       gs.log('Got Error: ' + err);
}

Output (Background Script):

The output shows the error, but thats just the logging. At the bottom you can see 'Got Result: null' which doesn't mean an error, just no return value from the script.

Root cause of JavaScriptException: org.mozilla.javascript.NativeError

JavaScript evaluation error on:

throw Error('stop');

: no thrown error

JavaScript evaluation error on:

throw Error('stop');

: org.mozilla.javascript.JavaScriptException: Error: stop (<refname>; line 1): org.mozilla.javascript.gen._refname__4578._c_script_0(<refname>:1)

org.mozilla.javascript.gen._refname__4578.call(<refname>)

org.mozilla.javascript.gen._refname__4578.exec(<refname>)

com.glide.script.ScriptEvaluator.execute(ScriptEvaluator.java:236)

com.glide.script.ScriptEvaluator.evaluateString(ScriptEvaluator.java:107)

com.glide.script.ScriptEvaluator.evaluateString(ScriptEvaluator.java:73)

com.glide.script.ScriptEvaluator.evaluateString(ScriptEvaluator.java:64)

com.glide.script.Evaluator.evaluateString(Evaluator.java:91)

sun.reflect.GeneratedMethodAccessor1891.invoke(Unknown Source)

sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

java.lang.reflect.Method.invoke(Method.java:498)

org.mozilla.javascript.MemberBox.invoke(MemberBox.java:138)

org.mozilla.javascript.NativeJavaMethod.call(NativeJavaMethod.java:292)

org.mozilla.javascript.ScriptRuntime.doCall(ScriptRuntime.java:2577)

org.mozilla.javascript.optimizer.OptRuntime.call1(OptRuntime.java:32)

org.mozilla.javascript.gen.null_null_4581._c_script_0(null.null:2)

org.mozilla.javascript.gen.null_null_4581.call(null.null)

org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:560)

org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3439)

org.mozilla.javascript.gen.null_null_4581.call(null.null)

org.mozilla.javascript.gen.null_null_4581.exec(null.null)

com.glide.script.ScriptEvaluator.execute(ScriptEvaluator.java:236)

com.glide.script.ScriptEvaluator.evaluateString(ScriptEvaluator.java:107)

com.glide.script.ScriptEvaluator.evaluateString(ScriptEvaluator.java:73)

com.glide.script.fencing.GlideScopedEvaluator.evaluateScript(GlideScopedEvaluator.java:324)

com.glide.script.fencing.GlideScopedEvaluator.evaluateScript(GlideScopedEvaluator.java:285)

com.glide.script.fencing.GlideScopedEvaluator.evaluateScript(GlideScopedEvaluator.java:256)

com.glide.script.fencing.GlideScopedEvaluator.evaluateScript(GlideScopedEvaluator.java:244)

com.glide.processors.ScriptProcessor.evaluateScript(ScriptProcessor.java:321)

com.glide.processors.ScriptProcessor.runScript(ScriptProcessor.java:216)

com.glide.processors.ScriptProcessor.process(ScriptProcessor.java:174)

com.glide.processors.AProcessor.runProcessor(AProcessor.java:412)

com.glide.processors.AProcessor.processTransaction(AProcessor.java:187)

com.glide.processors.ProcessorRegistry.process(ProcessorRegistry.java:165)

com.glide.ui.GlideServletTransaction.process(GlideServletTransaction.java:49)

com.glide.sys.ServletTransaction.run(ServletTransaction.java:34)

java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

java.lang.Thread.run(Thread.java:748)

*** Script: Got Result: null

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6 REPLIES 6

sergiu_panaite
ServiceNow Employee
ServiceNow Employee

‎08-31-2017 05:10 AM

Are you talking about capturing the stack trace rather than the error itself?



If yes, this might help:



How to Print Stack Trace via Script


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onnosteenbergen
Kilo Explorer
In response to sergiu_panaite

‎08-31-2017 05:15 AM

I need the error itself, or at least know that the evaluator encountered an error. Stacktracing example only works when you have an error.


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sergiu_panaite
ServiceNow Employee
ServiceNow Employee
In response to onnosteenbergen

‎08-31-2017 07:14 AM

I probably need to look a bit more into GlideEvaluator, see following test that looks strange to me:



var myvar;

try{

 myvar = (GlideEvaluator.evaluateString("gs.print('Testing');"));

} catch(e){

gs.print(e);

}


I get:



[0:00:00.004] Script completed in scope global: script

*** Script: Testing
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courtenay1
Tera Expert

‎10-02-2017 05:21 PM

Hi there,



It's the context of GlideEvaluator that it is running in.


You could wrap the script string to be evaluated in a try/catch   e.g. ...


var myScript = "boo;";

var result = 'yep';

result = GlideEvaluator.evaluateString('try{' + myScript + '}catch(err){ "ERROR! " + err}');   

gs.info('Got Result: ' + result);   


myScript = "throw Error('stop');";

result = 'yeah';

result = GlideEvaluator.evaluateString('try{' + myScript + '}catch(err){ "EROOR!!! " + err}');   

gs.info('Got Result: ' + result);  


But seriously, don't do this with production code. You lose control by masking the results.


To paraphrase Peter Lyons, try/catch is bit of a fail.


Read and understand his article - javascript try catch is fail | Peter Lyons  


and the article he references - Joyent | Error Handling


... node-js centric but still very valid.



Courtenay


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