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Groovy Basics

Scripts in Teneo are written in Groovy or Java code. Apache Groovy is similar to Java but with an easier to learn syntax. More details on Groovy can be found here: http://groovy-lang.org. An overview of the differences between Groovy and Java can be found here: Differences with Java.

Groovy-logo.svg

This page will provide a quick overview of Groovy snippets and constructs that can come in handy in scripts in Teneo.

To print something to the Engine Ouput panel in tryout (and the console.log) use:

groovy

1println "Hello world!"
2

As you can see you don't need semi-colons to end statements in Groovy.

Variables

In Groovy you can use dynamic typing. You use the keyword def to define a variable.

groovy

1def x = true
2println x.getClass()
3
4x = 42
5println x.getClass()
6
7x = "Hello World"
8println x.getClass()
9

Results:

groovy

1class java.lang.Boolean
2class java.lang.Integer
3class java.lang.String
4

Strings

When using single quotes, you will use a standard Java String:

groovy

1def name = 'Dave'
2println 'Hello, ' + name + '. You\'re looking well today.'
3

When using double quotes, you can use interpolation:

groovy

1def name = "Dave"
2println "Hello, ${name}. You're looking well today."
3

Substrings

groovy

1def text = "Hunky dory!"
2def name = text[0..4]
3println name
4

Result:

groovy

1Hunky
2

Other example:

groovy

1def text = "Hunky dory!"
2def name = text[-5..-2]
3println name
4

Result:

groovy

1dory
2

The Groovy Truth

Groovy evaluates every object to a boolean value if required (also know as the Implicit Truth):

groovy

1if ("hunky dory") ...
2if (42) ...
3if (someObject) ...
4
  • Strings: If empty false, otherwise true
  • Collections and Maps: true if they are not empty
  • Numbers: true if non-zero
  • Object references: true if they aren't null

For more details: Groovy Truth

Operators

Safe Navigation Operator

The Safe Navigation operator is used to avoid a NullPointerException. Typically when you have a reference to an object you might need to verify that it is not null before accessing methods or properties of the object. In Java it would look something like this:

java

1if (order.getContact() != null && order.getContact().getAddress() != null) { 
2	System.out.println(order.getContact().getAddress());
3}
4

In Groovy:

groovy

1println  order?.getContact()?.getAddress()
2

Elvis Operator

The "Elvis operator" is a shortening of the ternary operator, often used to assign default values. In Java you would use them like this:

groovy

1displayName = user.name ? user.name : 'Anonymous' 
2

Using the Elvis operator in Groovy:

groovy

1displayName = user.name ?: 'Anonymous'
2

(If you are wondering why it is called the Elvis operator, turn your head sideways and look at the smiley's hair.)

More on operators in the Groovy docs: Operators

Collections

Lists

Creating a list:

groovy

1def list = [1,2,2,4,5]
2

Accessing elements in the list:

groovy

1println list[0] // will print out 1 
2println list[-1] // use negative indexes for access from the end of the list, will print 5
3

Iterating lists:

groovy

1list.each {
2	println it
3}
4

or

groovy

1list.each { myNumber ->
2    println myNumber
3}
4

With index:

groovy

1list.eachWithIndex { myNumber,  index ->
2    println "$index, $myNumber"
3}
4

Will print:

groovy

10, 1
21, 2
32, 2
43, 4
54, 5
6

Quick way of adding something to a list:

groovy

1list << 6 // list will become [1,2,2,4,5,6]
2

Maps

Creating a map:

groovy

1def map = ['key1':'value 1', 'key2':'value 2', 'key3':'value 3']
2

Other options:

groovy

1def key = 'key3'
2def map = [
3  'key1': 'value 1',
4  key2: 'value 2', // skip the quotes, the key will automatically be a String
5  (key): 'value 3' // put the key in parentheses if you want to use the value of a variable
6]
7

Accessing the map:

groovy

1println map['key1']
2println map.key1
3println map[key] // access the entry with the value of key variable
4println map.get(key) // using the get method with a key variable
5

Iterating maps:

groovy

1map.each {
2  println it.key
3  println it.value
4}
5

or:

groovy

1map.each { key, value ->
2  println key
3  println value
4}
5

Adding something to a map:

groovy

1map << ['key4':'value 4']
2

For more information on lists and maps in Groovy: Working with collections

JSON

Groovy's handling of JSON is very powerful.

Parsing JSON

groovy

1def jsonSlurper = new groovy.json.JsonSlurper()
2def object = jsonSlurper.parseText('{"name": "Dave Bowman",  "age": 32 }')
3

Producing JSON

Using JsonOuput:

groovy

1def json = new groovy.json.JsonOutput().toJson([name: 'Dave Bowman', age: 32])
2
3// indent nicely
4def pretty = new groovy.json.JsonOutput().prettyPrint(json)
5

Using JsonBuilder:

groovy

1def actionBuilder = new groovy.json.JsonBuilder()
2
3actionBuilder {
4    name "displayCard"
5    parameters {
6        type 'basic'
7        title 'Cappuccino'
8        image 'https://some.url/for/image/cappuccino.png'
9        description 'Try our cappuccino! We love it for its remarkable body of fruit and mocha and its subtle sweet finish.'
10    }
11}
12def json = actionBuilder.toString()
13
14// indent nicely
15def pretty = groovy.json.JsonOutput.prettyPrint(json)
16
17println pretty
18

Result:

groovy

1{
2    "name": "displayCard",
3    "parameters": {
4        "type": "basic",
5        "title": "Cappuccino",
6        "image": "https://some.url/for/image/cappuccino.png",
7        "description": "Try our cappuccino! We love it for its remarkable body of fruit and mocha and its subtle sweet finish."
8    }
9}
10

More on Groovy's way of handling JSON here: Parsing and producing JSON

Reading URL content

Getting a URL

groovy

1def baseUrl = 'https://some/url/'
2def text = baseUrl.toURL().text
3

Getting a URL and parsing the JSON response

groovy

1def baseUrl = 'https://some/url/'
2def result = new groovy.json.JsonSlurper().parseText(baseUrl.toURL().text)
3

Setting a time out on requests

groovy

1def baseUrl = 'https://some/url/'
2def result = new groovy.json.JsonSlurper().parseText(baseUrl.toURL().getText([connectTimeout: 2000, readTimeout: 2000]))
3

If it takes a long time for Teneo to respond and you see an error like this in Tryout: Script action execution failed: Maximum execution time exceeded, but forced script termination failed, the cause is often a call to an online API that is slow or doesn't respond. Setting a timeout will prevent this error. However, you will still need to make sure that your script or flow gracefully handles the fact that it did not receive a response in time.