Groovy best pratices at EWAY

1. v
Groovy in production
Đào Văn Hiệp - 2018/08/10

2. Các vấn đề hiện tại?

3. Agenda:
- What is Groovy?
- How Groovy work?
- Why Groovy?
- Groovy vs Java
- Best practice with Groovy in production

4. Let's Go!

5. What is groovy?
Groovy is
A feature-rich
Java-friendly
Dynamic language *
For the Java platform
=> A super version of Java

6. What is a dynamic language?
A language that allows the types of variables to be changed at
runtime...
...among other things!
Difference between dynamic vs static language?

7. Groovy History
• 2003: Started by James Strachan and Bob McWhirter.
• 2004: Commissioned into JSR 241 but was almost abandoned.
• 2005: Brought back to life by Guillaume Laforge and Jeremy
• Rayner.
• 2007: Groovy 1.0.
• 2012: Groovy 2.0.
• 2014: Groovy 2.3 (official support for JDK 8)
• Now : Groovy 2.5 (Stable version)

8. Who use Groovy?
http://groovy-lang.org/

9. How Groovy work?
- Groovy runs in the JVM.
- GDK extend JDK
=> Groovy is syntactically aligned with Java.
- Compile to Bytecode like Java

10. Groovy Pos (vs. Java)
• Easy to learn
• Productivity (More concise and
meaningful code - Funny typing)
• Can call on Java classes. (Coding
link Java)
• Faster in develop, testing
• Addtional operators
• Mix Functional with Object Orient
Programming (Closure)

11. Groovy Cons (vs. Java)
• Nhiều lỗi tiềm ẩn với dynamic
coding: sai kiểu dữ liệu,....
• IDE không nhắc handle
exception
• Slower than Java

12. Demo

13. Groovy Features
• Closures
• Collection literals
• Properties (GroovyBeans or POGO)
• Multi-line strings
• String interpolation
• Default arguments
• Everything’s an Object (even numbers)
• Operator overloading
• GPath expressions
• Additional operators
• And much much more...

14. Closures are anonymous functions that:
o may accept parameters or return a value,
o can be assigned to variables,
o can be passed as arguments,
Demo
Groovy Closure

15. A both can take params, return value & do something, but...
Lambda expressions:
Language facility for implementing functional interfaces
• Interfaces with a single abstract method.
• Function, Predicate, Supplier, Consumer.
Groovy closures:
• Can be assign as variable
• Can be reference to default param by "it"
• Use like Functional Programming
Groovy Closure <> Java 8 Lambda

16. Groovy best practices

17. "def" keyword
Người đọc không hiểu dữ liệu trả về.
(Đặc biệt với đoạn dài)
=> Gây khó khi đọc hiểu & maintain

18. Don't use "if" with Object
Groovy truth and equals
• Null value is false.
• Empty collection or map is false.
• Empty string is false.
• Zero value is false.
Best pratices:
- Chỉ nên sử dụng với Boolean
- Các trường hợp dùng với Type Number
rất dễ nhầm
- Các trường hợp check List/String nên
check cả null
(StringUtils.notBlank()/CollectionUtils.notEmpty())

19. Don't use "if" with Object

20. • GString. (Double quote: "This is GString: ${1 + 1}")
Can be calculate, evaluate method....
• String.
• Single quote: 'This is String'
• Double quote: "This is String" - Like Java String
=> Don't use GString when unnecessary (String constant)
String vs GString

21. Use multiple line
String vs GString

22. "?:" operator
=> Hữu dụng khi dùng để set default
value
Vấn đề:
- Các trường hợp String blank hoặc Number
value 0
- KQ: 10 & 10​

23. Null Safe operator
With Null safe
Without Null safe

24. with() method
Check condition
Set multiple value
Use like builder

25. Collection In Groovy
• Find/Filter
• Map
• List to Map
• Grep (exclude null, empty elements)

26. Format Map, Json
Before
After

27. • Use operator : '==' (compare String), '=~' (Check regular/Contains)
• Operator: '+', '-' (add, remove with List)
• Parse Date: Date.parse(...), Date.format(...)
Groovy best practices (Continues)

28. • Annotations:
• @InheritConstructors
• @TupleConstructor
• @Slf4j
• @CompileStatic
• @Singleton
Groovy best practices (Continues)

29. • Groovy 2 Cookbook
• Programming Groovy 2
• Blog: http://mrhaki.blogspot.com
• Groovy Web Site: http://groovy.codehaus.org
How to start with Groovy?