19l04-roberts-advanced scripting and debugging

8/3/2019 19L04-Roberts-Advanced Scripting and Debugging

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Advanced Scripting &

Debugging Lab

John RobertsApplication Developer

ServiceNow

Jerrod BennettSenior Technical Consultant

ServiceNow


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Place holder for instanceinformation


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Overview Scripting & Debugging Concepts Debugging Tools

Client and Server Debugging Examples Extending Script Includes AJAX Debugging Basic Jelly Debugging Display Business Rules

Lab Agenda


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Overview

Disclaimer Advanced topics and quick pace Assumes some scripting experience and knowledge of

Service-now.com concepts

Objectives Improve scripting and troubleshooting abilities Learn some new tricks


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Overview

Setup Lab instance Script source - http://wiki.service-now.com/index.php?

title=Script_Lab

Optional Install Firefox and Firebug


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Scripting Concepts (quick review)

Case SenSitiviTy All commands, functions, variables,

Variable Scope Session global risk of duplication Classes limited to class Function limited to function, best protection

var myName = john;

function doThis() {var myName = roberts;

}


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Reference vs Value values Reference var myId = gr.sys_id;

myId will change as gr changes Value var myId = gr.sys_id.toString();

myId will only change if explicitly changed


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Try/Catch blocks for proper error handling Errors will halt script unless handled

try {

//something

}

catch (err) {

gs.log(ERROR: + err);

}


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Debugging Concepts

Know what should happen

Identify what is happening

Did my script run, were there errors

Do I have the expected results


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Debugging Tools

Application System Diagnostics / Session Debug modules Information output options

Browser Developer Tools Add-ons such as Firebug


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Debugging Examples

Exercise 1Business Rule Debug


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Exercise 1 Debug Business Rule

Scenario: business rule adds comments when incident state changesto closed

Problem: no comments are being added Business rule: k11 Exercise 1 Incident Close Comment


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Try it Open an existing incident Set incident state to Closed Using header context menu, save the record

Result No comment or info message

Troubleshooting Did the rule execute


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Identifying whether a business rule was executed Run the Debug Business Rules module to enable business rule

debugging

Just the Debug Business Rule, no jumping ahead to (Details) yet

Open anotherexisting incident and set incident state to closed,save

Scroll down to see debug output and notice the followingSkipping 'k11 Exercise 1 - Incident Close Comment' on table incident; condition not satisfied:

current.incident_state.changesTo("Closed")

From the debug output click on the business rule name to open it


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For some reason our condition is not being satisfied current.incident_state.changesTo("Closed")

Lets remove the condition and find out what the field value ischanging to

Delete the condition so the rule will execute Comment out the comment set statement so it doesnt run on all incidents Add some debugging statements

//add comment when closing//current.comments = "Closed by " + gs.getUserName() + " at " + gs.nowDateTime();//gs.addInfoMessage("Close comment added");// Debug infogs.addInfoMessage("(InfoMessage) Incident state = "+ current.incident_state);//output to appgs.log("(Log) Incident state = "+ current.incident_state);//output to system loggs.print("(debug print) Incident state = "+ current.incident_state);//output to debug console


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Open anotherexisting incident and set incident state to closed,save

Scroll down to see debug output and notice the following3:50:23.714: ==> 'k11 Exercise 1 - Incident Close Comment' on table incident

13:50:23.718: : (Log) Incident state = 7

13:50:23.718: : (debug print) Incident state = 7

13:50:23.719:


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Perform one more test to verify If we suspected the field value was wrong we could have taken a

shortcut

From a closed incident form, use the header context menu Show XML to displayall fields and values


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Debugging Examples

Exercise 2Debug Business Rule Changes


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Exercise 2 Business Rule Changes

Scenario: whenever we create a hardware incident the priority is setto 1, we suspect it might be a business rule

Try it Create a new incident and set category to Hardware

Save the incident, and notice the priority value has changed to 1

Debugging Enable the Debug Business Rule (Details) to add detail to the debug output Create another hardware incident, save View debug output

==> 'k11 Exercise 2 - Incident Priority Change' on table incidentpriority: 4 => 1


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Debugging Examples

Exercise 3Try Catch

Line by line evaluation


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Exercise 3 Error Handling

Scenario: simple business rule should add message when saving asoftware incident

Problem: we are only getting one of the three messages we expect

Try it Create a incident with software category Add a short description and save Notice we are getting one message at the top of the form


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Following the javascript processor line by line Run the JS Debug Activate module to enable the Rhino debugger Create another software incident and view the debug output Search the page for Exercise 3 to find the related script processing

==> 'k11 Exercise 3 - Display Info' on table incident

evaluate://output current number gs.addInfoMessage("Current number: " + current.number); //output current

short_description gs.addInfoMessage("Current Short Description: " + currrent.short_description); //outputcurrent category gs.addInfoMessage("Current Category: " + current.category);

>>> line(2) gs.addInfoMessage("Current number: " + current.number);

>>> line(5) gs.addInfoMessage("Current Short Description: " + currrent.short_description);


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Enable both Debug Business Rule and Debug Log modules Create another software incident and view the debug output Notice that we have a script exception because we have an extra r

in current


Evaluator: org.mozilla.javascript.EcmaError: "currrent" is not defined. Caused by error in Business Rule: 'k11Exercise 3 - Display Info' at line 5 2: gs.addInfoMessage("Current number: " + current.number); 3: 4: //output

current short_description ==> 5: gs.addInfoMessage("Current Short Description: " +currrent.short_description); 6: 7: //output current category 8: gs.addInfoMessage("Current Category: " +current.category);


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Add a try catch block around our statements and save the businessrule

try {//output current numbergs.addInfoMessage("Current number: "+ current.number);

//output current short_descriptiongs.addInfoMessage("Current Short Description: "+ currrent.short_description);//output current categorygs.addInfoMessage("Current Category: "+ current.category);

}catch(err) {

//catch only runs on exception in try block//err object is passed from the try handler and includesgs.log("Error in k11 Exercise 3 business rule: "+ err);

}


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Create one more software incident and see how the catchstatement provides information


: : Error in k11 Exercise 3 business rule: ReferenceError: "currrent" is not defined.


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Debugging Examples

Exercise 4Client Script


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Exercise 4 Client Script

Scenario: incident table has an on-change client script for categoryfunction onChange(control, oldValue, newValue, isLoading, isTemplate) {if (isLoading || newValue =='')

return;if (newValue =="request") {

g_form.setValue("urgency", 3);jslog("k11 Exercise 5 Request Category client script: Setting urgency to low

for requests");}

} Try it

Lets review options for client-side debug output Enable client javascript debugger console by clicking the green bug in the top

banner

Create a new incident, change category to request Script will log to debug console and change urgency to low Review debug console


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Using browser debuggers (Firebug) From a new incident form, open Firebug and make sure its active Go to the script tab and search for g_form.setValue("urgency,

so we can locate our script

Set a break point by clicking in the gray area left of the line numbers


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Change the category to request to execute the script again Firebug breakpoints can be funny at times, refresh the form script

does not stop at breakpoint

Review all the information available during the break You can also step through code using the yellow arrows


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Debugging Examples

Exercise 5Javascript Executor


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Exercise 5 Javascript Executor

Scenario: it would be nice to have a fast way to test client scriptswithout actually creating them first

Solution: Javascript executor has access to the same clientenvironment as client scripts

Try it: From a change request form, press to launch thejavascript executor

See that the description field is mandatory, lets test a script to change that g_form.setMandatory("description", false); Click Run My Code button Notice the mandatory flag has been removed, lets add it back and add a short

description

g_form.setMandatory("description", true); g_form.setValue(short_description, Testing);


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Exercise 5 Javascript Executor

Now for a cool admin trick Close the executor and verify that you cannot save the form with a

blank description field

Re-open the executorand run g_form.checkMandatory = false; Run My Code

Close executor Try to save the form again with a blank description You just temporarily bypassed the mandatory check on the form Use it wisely and keep it a secret


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Debugging Examples

Exercise 6Background Scripts


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Exercise 6 Background Scripts

Scenario: admin needs a way to test server side scripts or performsome maintenance that requires a script

Solution: background scripts are the server side version of Javascriptexecutor

Warning: this can really be dangerous, and even crash an entireinstance if you get something wrong


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Try it Lets build a script to disable some users Launch the background script module Enter the following script


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Notice that we have commented out the update line Its always best to see the possible results before you actually do

anything

Run the script to see the results

If this is a script you need frequently you can also save it to theserver Upload a script file with .js extension using the file upload

module

It will be available in the customer scripts for future reference andexecution

To be safe you can leave the function call commented when youupload so you purposely have to view and change it before it

does anything harmful


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Debugging Examples

Exercise 7Extending Script Includes


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Exercise 7 Extending Script Includes

Scenario: I like the functionality provided by the TableUtils scriptinclude but want to change it a bit

The getTables method in TableUtils class returns the parent list oftable hierarchy, but it returns it in a java array list not an array

For example you cant enumerate a java array list like you would witha Javascript array

//enumerate java array listfor (var i=0; i < tables.size(); i++) {gs.print(tables.get(i));}//enumerate javascript arrayfor (var i=0; i < tableArray.length; i++) {gs.print(tableArray[i]);}


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Try it From background scripts get the tables hierarchy for cmdb_ci_win_server

var util =new TableUtils("cmdb_ci_server");//getTables returns a java array list object, not arrayvar tables = util.getTables();gs.print("Java list: "+ tables);//what is the tables object

JSUtil.logObject(tables, "tables");//enumerate java array listfor (var i=0; i < tables.size(); i++) {

gs.print(tables.get(i));}

We could convert the array list to an array whenever we need it but it would benice to change the getTables method to return an array Modifying an out-of-box script include is never recommended

*** Script: Java list: [cmdb_ci_server,cmdb_ci_computer, cmdb_ci_hardware,

cmdb_ci]*** Script: Log Object: tables

Java Object:com.glide.util.ImmutableArrayList*** Script: cmdb_ci_server

*** Script: cmdb_ci_computer*** Script: cmdb_ci_hardware

*** Script: cmdb_ci


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Try it Lets first look at the TableUtils script includeinitialize: function(tableName){

this.tableName = tableName;},,getTables: function(){

var tables = Packages.com.glide.db.DBObjectManager.get().getTables(this.tableName); return tables;},

Theres another script include we can use to convert java objects tojavascript, thats j2js


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Since we dont want to modify the system script include well create ourown. We could make a full copy but that would be a waste, when we

can extend the class and leverage everything thats already in place.

Create a new script include for the MyTableUtils class Extending can add to or replace methods from the parent class

var MyTableUtils = Class.create();MyTableUtils.prototype = Object.extendsObject(TableUtils, {

getTablesArray: function() { var tables = this.getTables(); return j2js(tables);

},type: "MyTableUtils"

});

Save the record so we can test it


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Return to background scripts and call the new classvar util =new MyTableUtils("cmdb_ci_server");//call our new methodvar tables = util.getTables();gs.print("Java list: "+ tables);JSUtil.logObject(tables, "tables");gs.print("");

var tablesArray = util.getTablesArray();gs.print(tablesArray);JSUtil.logObject(tablesArray, "tablesArray");//what is util objectJSUtil.logObject(util, "util");

Notice that we didnt need an initialize of getTables method in our class,we inherited those from the parent (this) object


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Debugging Examples

Exercise 8AJAX Debugging


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Exercise 8 AJAX

Scenario: Use AJAX to lookup the number of available developmentlaptops when someone attempts to request one through the catalog Components

Catalog client script to submit AJAX request to server AJAX processor script include to perform the check and return the result to client Catalog client script to process the AJAX response and inform the user

Try it Go to the catalog and load the Development Laptop item Script runs on load to check inventory and alerts user with status from server


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Exercise 8 AJAX

Review scripts Review catalog client script k11 Capacity Check Review script include k11 CatalogCapacityCheck

Debugging options Log statements in script include Firebug to inspect payload to/from server Manual client script testing from javascript executor


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Exercise 8 AJAX

Try it From the development laptop catalog item page start the javascript executor

Run the following script to make an AJAX requestvar gajax =new GlideAjax("CapacityCheckAjax");gajax.addParam("sysparm_name", "checkDevCapacity");gajax.getXML(ajaxResponse);function ajaxResponse(serverResponse) {

alert(serverResponse.responseText);}


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Debugging Examples

Exercise 9Jelly


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Exercise 9 Jelly

Scenario: In a jelly script such as a UI Page, I would like to knowwhich jelly variables are available and what the values are Options

For known variables you can write values to HTML output Use breakpoint tag to view all available variables in a given phase

Jelly in 30 seconds XML files executed on server and output as HTML to client Evaluated in two phases, {phase 1} is cached (content), [phase 2] for data Nested structures with variables typically being passed down (UI Page calls a UI

Macro)


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Exercise 9 Jelly

Try it Review UI page k11_test Notice thej:set and j2:set lines setting values for jvar_p1_test and jvar_p2_test Review UI macro k11_macro_test called from the UI page Notice the references to the variables defined in the j:set and j2:set lines in the

UI page

Enable Debug Log so we can view of out of the macro breakpoints Navigate browser to /k11_test.do Examine the debug information Notice how our jvar_p1_test and jvar_p2_test only have value in their respective

phases


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Debugging Examples

Exercise 10Display Business Rules


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Exercise 10 Display Business Rules

Scenario: a client script needs to access data from a field that is notdisplayed on the form Options

Add the field to the form view and hide it using a UI policy Use a client GlideRecord query using AJAX Use a display business rule to preload an object that is passed to the client

Display business rules are processed on the server before the recorddata is passed to the client

The g_scratchpad object is available for setting values in the ruleand getting values on the client

Display rules can also change field data, similar to calculated fieldssince they display the new value but its not written to the database

until you save the record


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Review business rule k11 Exercise 10 Send data to the clienton the problem table//get the record sys_created_by value and add to the client scratchpadg_scratchpad.created_by = current.sys_created_by;//calculate the age of this recordvar age = gs.dateDiff(current.sys_created_on, gs.nowDateTime(), true);var daysOld = Math.round(age /3600/24);g_scratchpad.days_old = daysOld;

Review the client script k11 Exercise 10 - notify on oldproblems on problem tablefunction onLoad() {

//get data from display rule scratchpadvar createdBy = g_scratchpad.created_by;var daysOld = g_scratchpad.days_old;if (parseInt(daysOld) >30) {

alert("This is an old record created by "+ createdBy);}

}


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Try it Open the list of problems and find one that was created more than 30 days ago Notice the alert from the client script


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Q & A

j_roberts

#know11

#servicenow


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Additional Resources

SlightlyLoony blog (Service-now.com developer) http://community.service-now.com/blog/slightlyloony Wiki Script Portal

http://wiki.service-now.com/index.php?title=Scripting_and_APIs

JavaScript book JavaScript The Definitive Guide (OReilly)

W3Schools script and HTML reference http://www.w3schools.com

Firebug http://getfirebug.com/


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