ServiceNow Knowledge11 Advanced Scripting & Debugging Lab

Advanced Scripting &
Debugging Lab
John Roberts Jerrod Bennett
Application Developer Senior Technical Consultant
ServiceNow ServiceNow

Lab Agenda
•  Overview
•  Scripting & Debugging Concepts
•  Debugging Tools
•  Client and Server Debugging Examples
•  Extending Script Includes
•  AJAX Debugging
•  Basic Jelly Debugging
•  Display Business Rules

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

Overview
•  Setup
•  Lab instance
•  Script source - http://wiki.service-now.com/index.php?
title=Script_Lab

•  Optional
•  Install Firefox and Firebug

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”;

func4on
doThis()
{

var
myName
=
“roberts”;

}

•  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

•  Try/Catch blocks for proper error handling

•  Errors will halt script unless handled

try {
//something
}
catch (err) {
gs.log(“ERROR: “ + err);
}

Debugging Concepts
•  Know what should happen

•  Identify what is happening

•  Did my script run, were there errors

•  Do I have the expected results

Debugging Tools
•  Application
•  System Diagnostics / Session Debug modules
•  Information output options

•  Browser
•  Developer Tools
•  Add-ons such as Firebug

Debugging Examples
Exercise 1
Business Rule Debug

Exercise 1 – Debug Business Rule
•  Scenario: business rule adds comments when incident state changes
to closed
•  Problem: no comments are being added
•  Business rule: k11 Exercise 1 – Incident Close Comment

•  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

•  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 another existing incident and set incident state to closed,
save

•  Scroll down to see debug output and notice the following
Skipping '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

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

•  Let’s remove the condition and find out what the field value is
changing to
–  Delete the condition so the rule will execute
–  Comment out the comment set statement so it doesn’t 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 info
gs.addInfoMessage("(InfoMessage) Incident state = " + current.incident_state); //output to app
gs.log("(Log) Incident state = " + current.incident_state); //output to system log
gs.print("(debug print) Incident state = " + current.incident_state); //output to debug console

•  Open another existing incident and set incident state to closed,
save
•  Scroll down to see debug output and notice the following
3:50:23.714: ==> '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: <== 'k11 Exercise 1 - Incident Close Comment' on table incident

•  Looks like we had the wrong condition value for closed incident state
•  Now we can correct the condition and un-comment the business
rule

•  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 display
all fields and values

Debugging Examples
Exercise 2
Debug Business Rule Changes

Exercise 2 – Business Rule Changes
•  Scenario: whenever we create a hardware incident the priority is set
to 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 incident
priority: 4 => 1
<== 'k11 Exercise 2 - Incident Priority Change' on table incident

–  Looks like we found the rule changing the priority value

Debugging Examples
Exercise 3
Try … Catch
Line by line evaluation

Exercise 3 – Error Handling
•  Scenario: simple business rule should add message when saving a
software 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

•  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); //output
current 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);
<== 'k11 Exercise 3 - Display Info' on table incident

•  Notice we don’t process after line 5, now we need to find out why
•  First disable the rhino debugger by running the Disable All module
–  Rhino debugger can interfere or suppress error output

•  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: 'k11
Exercise 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);


•  Now let’s see how try … catch block can help us
•  From the debug output click on the business rule to open it

•  Add a try catch block around our statements and save the business
rule

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

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

//output current category
gs.addInfoMessage("Current Category: " + current.category);
}
catch(err) {
//catch only runs on exception in try block
//err object is passed from the try handler and includes
gs.log("Error in k11 Exercise 3 business rule: " + err);
}

•  Create one more software incident and see how the catch
statement provides information

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

•  Unhandled errors can prevent script functionality and even other
scripts from running
•  Catch statements guarantee that you control what happens when an
error occurs, especially important if you need to clean up or revert
something

Debugging Examples
Exercise 4
Client Script

Exercise 4 – Client Script
•  Scenario: incident table has an on-change client script for category
function 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
–  Let’s 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

•  Using browser debuggers (Firebug)

•  From a new incident form, open Firebug and make sure it’s 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

•  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

Debugging Examples
Exercise 5
Javascript Executor

Exercise 5 – Javascript Executor
•  Scenario: it would be nice to have a fast way to test client scripts
without actually creating them first
•  Solution: Javascript executor has access to the same client
environment as client scripts

•  Try it:
–  From a change request form, press <Shift><Ctrl><Alt><j> to launch the
javascript executor
–  See that the description field is mandatory, let’s test a script to change that
–  g_form.setMandatory("description", false);
–  Click Run My Code button
–  Notice the mandatory flag has been removed, let’s add it back and add a short
description
–  g_form.setMandatory("description", true);
–  g_form.setValue(“short_description”, “Testing”);

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 executor and 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

Debugging Examples
Exercise 6
Background Scripts

Exercise 6 – Background Scripts
•  Scenario: admin needs a way to test server side scripts or perform
some maintenance that requires a script

•  Solution: background scripts are the server side version of Javascript
executor

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

•  Try it
–  Let’s build a script to disable some users
–  Launch the background script module
–  Enter the following script

•  Notice that we have commented out the update line
•  It’s 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 the
server
•  Upload a script file with “.js” extension using the file upload
module
•  It will be available in the customer scripts for future reference and
execution
•  To be safe you can leave the function call commented when you
upload so you purposely have to view and change it before it
does anything harmful

Debugging Examples
Exercise 7
Extending Script Includes

Exercise 7 – Extending Script Includes
•  Scenario: I like the functionality provided by the TableUtils script
include but want to change it a bit

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

•  For example you can’t enumerate a java array list like you would with
a Javascript array
//enumerate java array list
for (var i=0; i < tables.size(); i++) {
gs.print(tables.get(i));
}

//enumerate javascript array
for (var i=0; i < tableArray.length; i++) {
gs.print(tableArray[i]);
}

•  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 array
var tables = util.getTables();
gs.print("Java list: " + tables); ***
Script:
Java
list:
[cmdb_ci_server,

//what is the tables object cmdb_ci_computer,
cmdb_ci_hardware,

JSUtil.logObject(tables, "tables"); cmdb_ci]

***
Script:
Log
Object:
tables

Java
Object:
com.glide.u@l.ImmutableArrayList

//enumerate java array list ***
Script:
cmdb_ci_server

for (var i=0; i < tables.size(); i++) { ***
Script:
cmdb_ci_computer

gs.print(tables.get(i)); ***
Script:
cmdb_ci_hardware

} ***
Script:
cmdb_ci

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

•  Try it
–  Let’s first look at the TableUtils script include

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

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

•  There’s another script include we can use to convert java objects to
javascript, that’s “j2js”

•  Since we don’t want to modify the system script include we’ll create our
own. We could make a full copy but that would be a waste, when we
can extend the class and leverage everything that’s 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

•  Return to background scripts and call the new class

var util = new MyTableUtils("cmdb_ci_server");
//call our new method
var 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 object
JSUtil.logObject(util, "util");

•  Notice that we didn’t need an initialize of getTables method in our class,
we inherited those from the parent (“this”) object

Debugging Examples
Exercise 8
AJAX Debugging

Exercise 8 – AJAX
•  Scenario: Use AJAX to lookup the number of available development
laptops 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

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

Exercise 8 – AJAX
•  Try it
–  From the development laptop catalog item page start the javascript executor
<Shift><Ctrl><Alt><j>

–  Run the following script to make an AJAX request

var gajax = new GlideAjax("CapacityCheckAjax");
gajax.addParam("sysparm_name", "checkDevCapacity");
gajax.getXML(ajaxResponse);

function ajaxResponse(serverResponse) {
alert(serverResponse.responseText);
}

Debugging Examples
Exercise 9
Jelly

Exercise 9 – Jelly
•  Scenario: In a jelly script such as a UI Page, I would like to know
which 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)

Exercise 9 – Jelly
•  Try it
–  Review UI page “k11_test”
–  Notice the j: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

Debugging Examples
Exercise 10
Display Business Rules

Exercise 10 – Display Business Rules
•  Scenario: a client script needs to access data from a field that is not
displayed 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 record
data is passed to the client
•  The “g_scratchpad” object is available for setting values in the rule
and getting values on the client
•  Display rules can also change field data, similar to calculated fields
since they display the new value but it’s not written to the database
until you save the record

•  Review business rule “k11 Exercise 10 Send data to the client”
on the problem table
//get the record sys_created_by value and add to the client scratchpad
g_scratchpad.created_by = current.sys_created_by;

//calculate the age of this record
var 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 old
problems” on problem table
function onLoad() {
//get data from display rule scratchpad
var createdBy = g_scratchpad.created_by;
var daysOld = g_scratchpad.days_old;

if (parseInt(daysOld) > 30) {
alert("This is an old record created by " + createdBy);
}
}

•  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

Q&A

j_roberts

#know11
#servicenow

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 (O’Reilly)

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

•  Firebug
–  http://getfirebug.com/

ServiceNow Knowledge11 Advanced Scripting & Debugging Lab

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