Key Points

1. Groovy is a dynamic language running on the JVM that fully integrates with Java
2. Groovy is an ideal language for advanced data management that relies on dynamic metadata and metamodels
3. Leverage Grade for builds and JCenter, Github, Mavencentral for libraries

References

Groovy Overviews

Udemy Complete Groovy Developer Course - updated for 4x - 2022

https://www.udemy.com/course/apache-groovy/

Groovy Tutorial For Beginners

https://www.youtube.com/watch?v=vDtENU-3Lwo

We will cover these Topics throughout the course

Programming Fundamentals Environment Setup Groovy Programming Basic Syntax Groovy Data Types Groovy Variables Groovy Operators Loops in Groovy Decision Making in Groovy Methods In Groovy File I/O in Groovy Optionals Data Structures Date & Time Exception Handling Object Oriented Programming Generics Closures Groovy Database

Groovy Script Tutorial for Beginners

What is a Groovy Script?
Why Groovy?
Groovy History
Features of Groovy
How to install Groovy
Groovy Hello World Example
Groovy Variables
Groovy-Operators
Groovy-Loops
Groovy- Decision Making
Groovy List
Groovy Maps
Groovy- Closures
Groovy Builders and Slurpers - Json etc
GORM for data access
Groovy Vs. Java
Myths about Groovy
Cons of using Groovy
Groovy Tools

Groovy Setup

SDKMAN ??

BREW ??

BINARY install and configuration

groovysh

groovyConsole

groovy SomeScript

setGroovy3.sh

Key Concepts

Summary of Key Groovy Concepts 

https://en.wikipedia.org/wiki/Apache_Groovy#History

1. Groovy uses and extends a Java JDK
2. Groovyc compiles Groovy source to executable classes with an option to capture the generated java source
3. Groovysh compiles Groovy source to execute from a command line
4. GroovyConsole provides a simple developer UI to build, test Groovy code and libraries
5. code can be dynamic or compiled and executes on a JVM
6. variables and properties can be static or dynamically typed
7. provides multiple programming models:  functional, object, object-oriented
8. Groovy Beans have more capability than Java beans and MBeans
   1. Java MBeans are management extended Beans ( see basic tutorial on MBeans )
9. Groovy extends the JDK with additional features and functions
10. can model event streams quickly using Gbeans as event sources, listeners, handlers for workflow modeling
11. Expando MetaClass allows dynamic class definitions at runtime ( a prototype model like JS and other languages )
12. Supports both immediate bindings of client to object ( like Java ) or deferred binding 
13. Excellent JSON and XML support to build, use those documents easily
14. String interpolation using Gstrings generates strings using embedded variable expressions
15. Dynamic compilation of code or strings to generate immediate executables at runtime ( provides "smart" system code generation dynamically )
16. Custom compilation of metaprogramming capabilities safely using AST transformations
17. AST Transformations provides Groovy with improved compile-time metaprogramming capabilities allowing powerful flexibility at the language level, without a runtime performance penalty
18. Traits are a structural construct of the language that allows: composition of behaviors, runtime implementation of interfaces, behavior overriding, and compatibility with static type checking/compilation.
19. Spock testing language is a BDD DSL that goes beyond Selenium, Cucumber, Gherkin
20. Grooscript converts Groovy code to JavaScript code.^[48] Although Grooscript has some limitations compared to Apache Groovy, it can use domain classes in both the server and the client.^[49] Plugin support for Grails version 3.0 is provided, as well as online code conversions.^[50]

Some key Groovy modeling scenarios

• from simple object models generate GORM classes and DDL in any database ( faster than building in data modeling tools or Erwin, System Architect, etc )
• generate prototype Web services and CRUD Web apps on the object models automatically to demo concepts to customers
• generate code dynamically at runtime based on event discovery for automated data conversion tooling
• use built-in event support and Expando metaclasses to generate dynamic event-driven workflows for clients

Grails - the fastest way to prototype services and Web UIs from executable object models in Groovy

• .. and then there's Grails ( better than Ruby on Rails )
• generates data access automatically to any database using Hibernate++ 
• generates service classes from object model classes
• generates CRUD Web UIs from object and service classes that support customized generation using templates
• I extended Grails to generate custom Web apps adding search to CRUD for ALL generations .. now SCRUD

Groovy Data Science libraries

Groovy - why I like it - Paul King

https://www.slideshare.net/paulk_asert/awesome-groovy

Object Computing - Groovy Data Science billable course

https://objectcomputing.com/services/training/catalog/grails/data-science-with-groovy

Using Groovy for Data Science - youtbue free

https://www.youtube.com/watch?v=rixvYN-DCPk

Groovy Data Science - Paul King - speakerdeck

https://speakerdeck.com/paulk/groovy-data-science

Groovy Tools - Paul King

https://www.slideshare.net/paulk_asert/industrial-strength-groovy-paul-king-may2009-1461116

Groovy data science concepts for beginners - Advent

https://www.javaadvent.com/2022/12/groovy-and-data-science.html

Groovy Expando - dynamic instance attributes, methods

//==============================
//x3001 Groovy expando metaclass for dynamic behavior ..

class FileUpdateMgr extends Expando {
}
FileUpdateMgr.metaClass.getDateNDaysFromNow = { days -> 
    def cal = new GregorianCalendar()
    cal.roll Calendar.DAY_OF_MONTH, days
    new java.text.SimpleDateFormat().format(cal.time)
}
def mgr = new FileUpdateMgr()
mgr.name = "Jim"
mgr.newDate = mgr.getDateNDaysFromNow(12)
println "$mgr.name "
println "newDate from now: $mgr.newDate"

Groovy Expando Classes packaged - gtwf1-test.groovy

package swt;

class ModelUser extends Expando {
    def methodMissing = { String name, args -> console.println "method> " || name  };
    def orderType;
} 
class ModelSystem extends Expando {
    def pout = { amsg -> console.println amsg  };
} 

// test case

def auser = new ModelUser()
auser.setOrderType( "network" )
println auser.getOrderType()



def system = new ModelSystem()
system.pout( "print a method call")

Groovy Beans - Object Properties and Listeners model dynamic event use cases

use object properties and listeners to simulate dynamic events in models

Groovy Beans PropertyChange Listeners - Event-driven software **

groovy-beans-propertyChange-listeners-2022-blog.mrhaki.com-Groovy Goodness Bound and Constrained Properties in GroovyBeans.pdf

example

/*
   x111c groovy bound property example - https://blog.mrhaki.com/2009/08/groovy-goodness-bound-and-constrained.html
*/

import groovy.beans.*
 
class Car {
   int numberOfDoors
   @Vetoable String model
   @Vetoable String brand
   boolean automatic
   @Bindable double price
  
   String toString() {
     "[Car details => brand: '${brand}', model: '${model}', #doors: '${numberOfDoors}', automatic: '${automatic}', price: '${price}']"
   }
}

import groovy.beans.*
import java.beans.*
 
def toyota = new Car(brand: 'Toyota', model: 'Verso', price: 28919, numberOfDoors: 5)
toyota.propertyChange = {
 if (it.propertyName == 'price') {
  println "The price has changed. Inform sales the new price is '${it.newValue}'."
 }
}
toyota.vetoableChange = { PropertyChangeEvent pce ->
 if (pce.propertyName == "brand") {
  if (!(pce.newValue in ['Toyota', 'Lexus'])) {
   throw new PropertyVetoException('New value is not Toyota or Lexus', pce)
  }
 }
 if (pce.propertyName == "model") {
  if (pce.newValue ==~ /.*\d+.*/) {
   throw new PropertyVetoException('No numbers in model names allowed.', pce)
  }
 }
}
 
toyota.price = 30995
assert 30995 == toyota.price
 
toyota.brand = 'Lexus'
assert 'Lexus' == toyota.brand
 
try {
 toyota.brand = 'AUDI'
 assert false: 'We should not be able to set this value.'
} catch (PropertyVetoException e) {
 assert true
 println " could not set brand to AUDI. car brand is ${toyota.brand}"
}
 
try {
 toyota.model = 'A5'
 assert false: 'We should not be able to set this value.'
} catch (PropertyVetoException e) {
 assert true
 println " could not set model to A5. car model is ${toyota.model}"
}

Groovy Expando example with PropertyChange listeners - Jim

//ex-expando-events-gen-v1.groovy

ex-expando-events-gen-v1.groovy
x111c groovy bound property example - https://blog.mrhaki.com/2009/08/groovy-goodness-bound-and-constrained.html
shows the flexibility of event messaging in requirements modeling

Event >> Owner Jim detected car Lexus automatic transmission type changed to: true from: false
the car is [Car details => brand: 'Lexus', model: 'Verso', #doors: '5', automatic: 'true', price: '30995.0']

Event >> Owner Jim detected car Lexus price changed to: 44000.0 from: 30995.0
the car is [Car details => brand: 'Lexus', model: 'Verso', #doors: '5', automatic: 'true', price: '44000.0']

ex-expando-events-gen-v1.groovy file

Traits vs Interfaces

https://www.baeldung.com/groovy-traits

Traits are reusable components representing a set of methods or behaviors that we can use to extend the functionality of multiple classes.

For this reason, they're considered as interfaces, carrying both default implementations and state. All traits are defined using the trait keyword.

Groovy 3 Key Features

http://groovy-lang.org/releasenotes/groovy-3.0.html

supports JDK 11, JDK 9 and JDK 8 at runtime

onlyJDK 11, JDK 9 supported at build time

Java-style Lambda syntax

(1..10).forEach(e -> { println e })

assert (1..10).stream()
                .filter(e -> e % 2 == 0)
                .map(e -> e * 2)
                .toList() == [4, 8, 12, 16, 20]

// general form
def add = (int x, int y) -> { def z = y; return x + z }
assert add(3, 4) == 7

// curly braces are optional for a single expression
def sub = (int x, int y) -> x - y
assert sub(4, 3) == 1

// parameter types are optional
def mult = (x, y) -> x * y
assert mult(3, 4) == 12

// no parentheses required for a single parameter with no type
def isEven = n -> n % 2 == 0
assert isEven(6)
assert !isEven(7)

// no arguments case
def theAnswer = () -> 42
assert theAnswer() == 42

// any statement requires braces
def checkMath = () -> { assert 1 + 1 == 2 }
checkMath()

// example showing default parameter values (no Java equivalent)
def addWithDefault = (int x, int y = 100) -> x + y
assert addWithDefault(1, 200) == 201
assert addWithDefault(1) == 101

Groovy 4 Features

Groovy 4 Overview Slides - Paul King

https://speakerdeck.com/paulk/groovy-roadmap

Query on Groovy Records, DBs later

https://speakerdeck.com/paulk/groovy-roadmap?slide=27

Now FMR ( Filter Map Reduce is done using SELECT )

GINQ - Groovy Integrated Query

GINQ console example

Groovy Switch can use ranges etc

Built in Type Checkers

Groovy Macro Methods

https://github.com/bsideup/groovy-macro-methods-proposal

AST Transformations

AST Transformation List

Records with meta-annotations

Design by Contract concept

Groovy Builders and Slurpers

Groovy JsonBuilder example

https://stackoverflow.com/questions/51068636/groovy-map-to-json-list-of-objects

to serialize map to json object (string)

you can use

http://docs.groovy-lang.org/latest/html/gapi/groovy/json/JsonBuilder.html

import groovy.json.JsonBuilder
new JsonBuilder([test: 'test', test2: 'test2']).toPrettyString()

or

http://docs.groovy-lang.org/latest/html/gapi/groovy/json/JsonOutput.html

import groovy.json.JsonOutput
JsonOutput.prettyPrint(JsonOutput.toJson([test: 'test', test2: 'test2']))

Spock Test Framework

http://spockframework.org/spock/docs/1.3/all_in_one.html

Spock Web Console

Spock Web Console is a website that allows you to instantly view, edit, run, and even publish Spock specifications. It is the perfect place to toy around with Spock without making any commitments. So why not run Hello, Spock! right away?

Spock Sample Project

To try Spock in your local environment, clone or download/unzip the Spock Example Project. It comes with fully working Ant, Gradle, and Maven builds that require no further setup. The Gradle build even bootstraps Gradle itself and gets you up and running in Eclipse or IDEA with a single command. See the README for detailed instructions.

Spock Overview

Spock lets you write specifications that describe expected features (properties, aspects) exhibited by a system of interest. The system of interest could be anything between a single class and a whole application, and is also called the system under specification or SUS. The description of a feature starts from a specific snapshot of the SUS and its collaborators; this snapshot is called the feature’s fixture.

Create Java source from compiled Groovy bytecode

JDs - java decompiler can convert groovy bytecode to Java source

https://www.javacodegeeks.com/2021/11/13-best-java-decompilers-for-download-and-online-use-for-java-developers.html

Potential Value Opportunities

Potential Challenges

Groovyc - compile groovy to generate class files

groovyc -h   // see all help

run groovyc in app folder with groovy files, dump classes to a classes subfolder

cd  /Volumes/GoogleDrive/'My Drive'/_work/learn/blearn-pc/groovy

groovyc -d classes < main groovy class or list of classes >

Bug> Groovyconsole can't open groovy file from menu or cli

bug> can't open a file from groovyconsole using the file menu

workaround> use CTL + O

1. open groovyconsole normally
2. use CTL + O to open file selector window
3. select a groovy file
4. press Enter
5. << file opens normally in groovy console

Candidate Solutions

Transform input string by line to output print stream

//===========================
// transform input string by line to output print stream

def s1 = """    originID: { type: mongoose.Schema.Types.ObjectId, ref: 'projects' },
    parentID: { type: String}, // Can be used to track the parent asset
    buyerAccountId: { type: mongoose.Schema.Types.ObjectId, ref: 'accounts', required: true },
    sellerAccountId: { type: mongoose.Schema.Types.ObjectId, ref: 'accounts', required: true }, //Can be null if direct buy from project
    paymentId: { type: String },
    paymentMethodId: { type: String },
    amount: { type: Number, required: true },
    orderNumber: { type: Number },
    paymentType: { type: String },
    pricePerUnit: { type: Number, required: true },
    qty: {type: Number, required: true, default: 0},
    description: {type: String},
    status: {type: String, required: true},
    productName: { type: String },
    buyerName: { type: String },
    sellerName: { type: String },
"""
def fields = []
def lines = s1.readLines()
lines.forEach{ 
fields = it.split(":");
println "    \"" + fields[0].replace(" ","") + "\":\"\",";
//println "    \"" + fields[0] + "\": true,";
}

Step-by-step guide for Example

sample code block

Groovy Work File examples 

Recommended Next Steps

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