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TIL
  • README
  • Git
    • Basic
    • Remote Repository
    • Log & Diff
    • Rebase&Cherri-Pick
    • git-flow
  • DevOps
    • Monolithic vs MSA
    • Jenkins ์‹œ์ž‘ํ•˜๊ธฐ
    • Airflow ์‹œ์ž‘ํ•˜๊ธฐ
    • Airflow ์‹œ์ž‘ํ•˜๊ธฐ
    • Build Tools
      • maven
  • ๊ฐœ๋ฐœ ๋ฐฉ๋ฒ•๋ก 
    • TDD
  • Spring
    • IoC
    • Is Spring Bean Thread-Safe?
    • Spring Singleton
    • Component Scan
    • Spring Annotation
    • ์˜์กด ๊ด€๊ณ„ ์ฃผ์ž…(DI)
    • Lombok ํ™œ์šฉํ•˜๊ธฐ
    • Bean ์ƒ๋ช…์ฃผ๊ธฐ์™€ ์ฝœ๋ฐฑ
    • Bean Scope
    • AOP(1) - AOP๋ž€
    • AOP(2) - Aop Proxy
    • AOP(3) - Dynamic Proxy
    • AOP(4) - AspectJ
    • POJO
    • Spring ์„œ๋น„์Šค ๊ตฌ์กฐ
    • Transaction
    • JPA๋ž€?
    • JPA Entity
    • Spring Data JPA
    • Spring Data Specification
    • Model Mapping
    • Cache
    • restTemplate
    • YAML ํŒŒ์ผ ์„ค์ •
    • Spring Boot
      • H2 DB ์„ค์ •
      • ๋‹ค์ค‘ ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์„ค์ •
      • Mybatis ์—ฐ๋™ํ•˜๊ธฐ
    • Spring Batch
      • Batch ์‹œ์ž‘ํ•ด๋ณด๊ธฐ
      • Batch Job Flow
      • Job
      • Step
      • Batch Scope & Job Parameter
      • JobRepository์™€ ๋ฉ”ํƒ€ํ…Œ์ด๋ธ”
      • Chunk ์ง€ํ–ฅ ํ”„๋กœ๊ทธ๋ž˜๋ฐ
      • ItemReader
      • ItemProcessor
      • ItemWriter
      • Batch Schedular
      • Job๋ณ„ Bean๋“ฑ๋กํ•˜๊ธฐ
      • Batch ๊ตฌํ˜„์‹œ ๋ฐœ์ƒํ•œ ์˜ค๋ฅ˜ ์ •๋ฆฌ
      • Spring Batch Scaling
        • Multithread Job๊ตฌํ˜„์‹œ ์ด์Šˆ์‚ฌํ•ญ
    • Spring test
      • Junit5
        • ํ…Œ์ŠคํŠธ ์ด๋ฆ„ ํ‘œ๊ธฐ
        • ํ…Œ์ŠคํŠธ ๊ทธ๋ฃน ์‚ฌ์ด์˜ ๊ด€๊ณ„
        • ํƒœ๊ทธ์™€ ํ•„ํ„ฐ๋ง
        • ๋™์  ํ…Œ์ŠคํŠธ
        • ํ…Œ์ŠคํŠธ LifeCycle
        • ํ…Œ์ŠคํŠธ ๋ฉ”์„œ๋“œ
        • ํ…Œ์ŠคํŠธ ์ˆœ์„œ
        • AssertJ
        • ํ…Œ์ŠคํŠธ ๋ณ‘๋ ฌ ์‹คํ–‰
        • AssertJ
        • Mock
      • Spring Boot Test DB ๋ถ„๋ฆฌ
      • Spring Batch Test
  • Web Application
    • Web Server & WAS
    • ๊ด€๋ จ ๊ฐœ๋… - HTTP API, HTML, CSR, SSR
    • Servlet
    • JSP
    • Cookie And Session
    • ์˜ˆ์™ธํŽ˜์ด์ง€
    • Java Bean
    • JDBC
    • Connection Pool
    • ํŒŒ์ผ ์—…๋กœ๋“œ
    • Expression Language
    • JSTL
    • FrontControllerํŒจํ„ด Command ํŒจํ„ด
    • Forwarding
    • MVC
    • ํšŒ์›๊ฐ€์ž…์˜ˆ์ œ
    • ์ฐธ๊ณ 
      • ๊ฐœ๋ฐœํ™˜๊ฒฝ์„ค์ •
  • Java+
    • SOAP/WSDL vs REST
    • WSDL์„ JAVA๋กœ ๋ณ€ํ™˜ํ•˜๊ธฐ
    • SOAP ํ†ต์‹  OPEN API๋กœ ๊ฐœ๋ฐœํ•ด๋ณด๊ธฐ
  • Java
    • Basic
      • ๋ณ€์ˆ˜์™€ ํƒ€์ž…
      • ์—ฐ์‚ฐ์ž
      • ์กฐ๊ฑด๋ฌธ๊ณผ ๋ฐ˜๋ณต๋ฌธ
      • ์ฐธ์กฐ ํƒ€์ž…
      • ํด๋ž˜์Šค
      • ์ƒ์†(Inheritance)
      • ์ธํ„ฐํŽ˜์ด์Šค(Interface)
      • ์ค‘์ฒฉ ํด๋ž˜์Šค์™€ ์ค‘์ฒฉ ์ธํ„ฐํŽ˜์ด์Šค
      • ์˜ˆ์™ธ ์ฒ˜๋ฆฌ
      • API - Object, System, Class, Math, Wrapper
      • API - String, StringBuffer, StringBuilder
      • Thread
      • Generic
      • Lambda
      • Collection - List, Set
      • Collection - Map
      • Collection - Tree
      • Collection - Stack, Queue
      • Stream
      • Reflection
      • ์ •๊ทœํ‘œํ˜„์‹
      • GUI
      • UML
      • Serializable
    • Advanced
      • OutOfMemoryError
      • AutoValue
      • meta-annotation
        • @Retention
        • @Target
        • @Repeatable
    • Effective Java 3/E
      • ITEM 1: Static Factory Method(์ •์  ๋ฉ”์†Œ๋“œ)
      • ITEM 2: Builder Pattern
      • ITEM 3: Singleton
      • ITEM 4: Private Constructor
      • ITEM 5: Dependency Injection
      • ITEM 6: Avoid Unnecessary Object
      • ITEM 7: Eliminate Object Reference
      • ITEM 8: Avoid finalizer and cleaner
      • ITEM 9: try-with-resources
      • ITEM 10: The gerneral contract when overriding equlas
      • ITEM 11: Overriding hashCode
      • ITEM 12: overriding toString
      • ITEM 13: overriding clone judiciously
      • ITEM 14: Consider implementing comparable
      • ITEM 15: ํด๋ž˜์Šค์™€ ๋ฉค๋ฒ„์˜ ์ ‘๊ทผ์„ ์ตœ์†Œํ™”ํ•ด๋ผ
      • ITEM 16: Use Accessor methods
      • ITEM 17: ๋ณ€๊ฒฝ ๊ฐ€๋Šฅ์„ฑ์„ ์ตœ์†Œํ™”ํ•ด๋ผ(๋ถˆ๋ณ€ ํด๋ž˜์Šค)
      • ITEM 18: ์ƒ์†๋ณด๋‹จ ์ปดํฌ์ง€์…˜์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 19: ์ƒ์†์„ ๊ณ ๋ คํ•ด ์„ค๊ณ„ํ•˜๊ณ  ๋ฌธ์„œํ™”ํ•ด๋ผ
      • ITEM 20: ์ถ”์ƒ ํด๋ž˜์Šค๋ณด๋‹ค ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์šฐ์„ ํ•˜๋ผ
      • ITEM 21: ์ธํ„ฐํŽ˜์ด์Šค๋Š” ๊ตฌํ˜„ํ•˜๋Š” ์ชฝ์„ ์ƒ๊ฐํ•ด ์„ค๊ณ„ํ•ด๋ผ.
      • ITEM 22: ์ธํ„ฐํŽ˜์ด์Šค๋Š” ํƒ€์ž…์„ ์ •์˜ํ•˜๋Š” ์šฉ๋„๋กœ๋งŒ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 23: ํƒœ๊ทธ ๋‹ฌ๋ฆฐ ํด๋ž˜์Šค๋ณด๋‹ค ํด๋ž˜์Šค ๊ณ„์ธต๊ตฌ์กฐ๋ฅผ ํ™œ์šฉํ•ด๋ผ
      • ITEM 24: ๋ฉค๋ฒ„ ํด๋ž˜์Šค๋Š” ๋˜๋„๋ก static์œผ๋กœ ๊ตฌํ˜„ํ•ด๋ผ
      • ITEM 25: ํ†ฑ๋ ˆ๋ฒจ ํด๋ž˜์Šค๋Š” ํ•œ ํŒŒ์ผ์— ํ•˜๋‚˜๋งŒ ์ƒ์„ฑํ•ด๋ผ.
      • ITEM 26: Raw type์€ ์‚ฌ์šฉํ•˜์ง€ ๋งˆ๋ผ
      • ITEM 27: ๋น„๊ฒ€์‚ฌ ๊ฒฝ๊ณ ๋ฅผ ์ œ๊ฑฐํ•ด๋ผ
      • ITEM 28: ๋ฐฐ์—ด๋ณด๋‹ค๋Š” ๋ฆฌ์ŠคํŠธ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 29: ์ด์™•์ด๋ฉด ์ œ๋„ค๋ฆญ ํƒ€์ž…์œผ๋กœ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 30: ์ด์™•์ด๋ฉด ์ œ๋„ค๋ฆญ ๋ฉ”์„œ๋“œ๋กœ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 31 : ํ•œ์ •์  ์™€์ผ๋“œ์นด๋“œ๋ฅผ ์‚ฌ์šฉํ•ด API ์œ ์—ฐ์„ฑ์„ ๋†’์—ฌ๋ผ
      • ITEM 32: ์ œ๋„ค๋ฆญ๊ณผ ๊ฐ€๋ณ€์ธ์ˆ˜๋ฅผ ํ•จ๊ป˜ ์“ธ ๋•Œ๋Š” ์‹ ์ค‘ํ•ด๋ผ
      • ITEM 33: ํƒ€์ž… ์•ˆ์ „ ์ด์ข… ์ปจํ…Œ์ด๋„ˆ๋ฅผ ๊ณ ๋ คํ•ด๋ผ
      • ITEM 34: int ์ƒ์ˆ˜ ๋Œ€์‹  ์—ด๊ฑฐ ํƒ€์ž…์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 35: ordinal ๋ฉ”์„œ๋“œ ๋Œ€์‹  ์ธ์Šคํ„ด์Šค ํ•„๋“œ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 36: ๋น„ํŠธ ํ•„๋“œ ๋Œ€์‹  EnumSet์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 37: ordinal ์ธ๋ฑ์‹ฑ ๋Œ€์‹  EnumMap์„ ์‚ฌ์šฉํ•ด๋ผ
      • TEM 38 : ํ™•์žฅํ•  ์ˆ˜ ์žˆ๋Š” ์—ด๊ฑฐํƒ€์ž…์ด ํ•„์š”ํ•˜๋ฉด ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 39: ๋ช…๋ช… ํŒจํ„ด๋ณด๋‹ค ์• ๋„ˆํ…Œ์ด์…˜์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 40: @Override ์–ด๋…ธํ…Œ์ด์…˜์„ ์ผ๊ด€๋˜๊ฒŒ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 41: ์ •์˜ํ•˜๋ ค๋Š” ๊ฒƒ์ด ํƒ€์ž…์ด๋ผ๋ฉด ๋งˆ์ปค ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 42: ์ต๋ช… ํด๋ž˜์Šค๋ณด๋‹ค๋Š” ๋žŒ๋‹ค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 43: ๋žŒ๋‹ค๋ณด๋‹ค๋Š” ๋ฉ”์„œ๋“œ ์ฐธ์กฐ๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 44: ํ‘œ์ค€ ํ•จ์ˆ˜ํ˜• ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 45: ์ŠคํŠธ๋ฆผ์€ ์ฃผ์˜ํ•ด์„œ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 46: ์ŠคํŠธ๋ฆผ์—์„œ ๋ถ€์ž‘์šฉ ์—†๋Š” ํ•จ์ˆ˜๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 47: ๋ฐ˜ํ™˜ ํƒ€์ž…์œผ๋กœ๋Š” ์ŠคํŠธ๋ฆผ๋ณด๋‹ค ์ปฌ๋ ‰์…˜์ด ๋‚ซ๋‹ค.
      • ITEM 48: ์ŠคํŠธ๋ฆผ ๋ณ‘๋ ฌํ™”๋Š” ์ฃผ์˜ํ•ด์„œ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 49: ๋งค๊ฐœ๋ณ€์ˆ˜๊ฐ€ ์œ ํšจํ•œ์ง€ ๊ฒ€์‚ฌํ•ด๋ผ
      • ITEM 50: ์ ์‹œ์— ๋ฐฉ์–ด์  ๋ณต์‚ฌ๋ณธ์„ ๋งŒ๋“ค์–ด๋ผ
      • ITEM 51: ๋ฉ”์„œ๋“œ ์‹œ๊ทธ๋‹ˆ์ฒ˜๋ฅผ ์‹ ์ค‘ํžˆ ์„ค๊ณ„ํ•ด๋ผ
      • ITEM 52: ๋‹ค์ค‘์ •์˜๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 53: ๊ฐ€๋ณ€์ธ์ˆ˜๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 54: null์ด ์•„๋‹Œ, ๋นˆ ์ปฌ๋ ‰์…˜์ด๋‚˜ ๋ฐฐ์—ด์„ ๋ฐ˜ํ™˜ํ•ด๋ผ
      • ITEM 55: Optional ๋ฐ˜ํ™˜์€ ์‹ ์ค‘ํ•˜๊ฒŒ ํ•ด๋ผ
      • ITEM 56: ๊ณต๊ฐœ๋œ API ์š”์†Œ์—๋Š” ํ•ญ์ƒ ์ฃผ์„์„ ์ž‘์„ฑํ•ด๋ผ
      • ITEM 57: ์ง€์—ญ๋ณ€์ˆ˜์˜ ๋ฒ”์œ„๋ฅผ ์ตœ์†Œํ™”ํ•ด๋ผ
      • ITEM 58: ์ „ํ†ต์ ์ธ for ๋ฌธ๋ณด๋‹ค๋Š” for-each๋ฌธ์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 59: ๋ผ์ด๋ธŒ๋Ÿฌ๋ฆฌ๋ฅผ ์ตํžˆ๊ณ  ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 60: ์ •ํ™•ํ•œ ๋‹ต์ด ํ•„์š”ํ•˜๋‹ค๋ฉด float์™€ double์€ ํ”ผํ•ด๋ผ
      • ITEM 61: ๋ฐ•์‹ฑ๋œ ๊ธฐ๋ณธ ํƒ€์ž…๋ณด๋‹ค๋Š” ๊ธฐ๋ณธ ํƒ€์ž…์„ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 62: ๋‹ค๋ฅธ ํƒ€์ž…์ด ์ ์ ˆํ•˜๋‹ค๋ฉด ๋ฌธ์ž์—ด ์‚ฌ์šฉ์„ ํ”ผํ•ด๋ผ
      • ITEM 63: ๋ฌธ์ž์—ด ์—ฐ๊ฒฐ์€ ๋А๋ฆฌ๋‹ˆ ์ฃผ์˜ํ•ด๋ผ
      • ITEM 64: ๊ฐ์ฒด๋Š” ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด ์ฐธ์กฐํ•ด๋ผ
      • ITEM 65: ๋ฆฌํ”Œ๋ ‰์…˜๋ณด๋‹ค๋Š” ์ธํ„ฐํŽ˜์ด์Šค๋ฅผ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 66: ๋„ค์ดํ‹ฐ๋ธŒ ๋ฉ”์„œ๋“œ๋Š” ์‹ ์ค‘ํžˆ ์‚ฌ์šฉํ•ด๋ผ
      • ITEM 67: ์ตœ์ ํ™”๋Š” ์‹ ์ค‘ํžˆ ํ•ด๋ผ
      • ITEM 68: ์ผ๋ฐ˜์ ์œผ๋กœ ํ†ต์šฉ๋˜๋Š” ๋ช…๋ช… ๊ทœ์น™์„ ๋”ฐ๋ผ๋ผ
    • ๊ฐ์ฒด์ง€ํ–ฅ ์„ค๊ณ„ ์›์น™(SOLID)
    • ๋””์ž์ธํŒจํ„ด
      • Strategy Pattern
      • Template Method Pattern
      • Factory Method Pattern
      • Singleton
      • Delegation
      • Proxy
      • Adapter Pattern
    • ์‹ค์Šต
      • ์ธํ„ฐํŽ˜์ด์Šค ์‹ค์Šต - Vehicle
      • ์ธํ„ฐํŽ˜์ด์Šค ์‹ค์Šต - Remote
      • GUI ์‹ค์Šต - Calculator
      • GUI ์‹ค์Šต - button
      • GUI ์‹ค์Šต - lotto
      • Thread ์‹ค์Šต - ์ขŒ์„์˜ˆ์•ฝ, ๋ฉ”์„ธ์ง€๋ณด๋‚ด๊ธฐ
    • Jar vs War
  • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค
    • KEY
    • Index
    • Transaction
    • Trigger
    • Procedure / Function
    • Package
    • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ๋ฐฐ์›€ํ„ฐ
      • ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์‹œ์Šคํ…œ
      • ๊ด€๊ณ„๋ฐ์ดํ„ฐ ๋ชจ๋ธ
      • ๊ด€๊ณ„๋Œ€์ˆ˜์™€ SQL
    • MySQL
      • Database๋ž€
      • MySQL ์‹œ์ž‘ํ•˜๊ธฐ
      • MySQL Database
      • MySQL Table
      • CRUD
      • ๊ด€๊ณ„ํ˜• ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค
      • Server์™€ Client
    • PostgreSQL
    • NoSQL
      • Install Cassandra on mac
      • Cassandra๋ž€?
      • NiFi๋ž€
  • Algorithm
    • String
    • Recursion
    • Dynamic Programming
    • Array, Struct, Pointer
    • Math
    • Sort
    • List
    • Stack
    • Queue
    • Graph
    • Tree
    • Maze
    • AVL
    • ์ด์ง„ํƒ์ƒ‰ํŠธ๋ฆฌ(Binary Search Tree)
    • DFS์™€ BFS
    • ๋‹ค์ต์ŠคํŠธ๋ผ ์•Œ๊ณ ๋ฆฌ์ฆ˜(Dijkstra's Algorithm)
    • Red-Black ํŠธ๋ฆฌ
    • A* ์•Œ๊ณ ๋ฆฌ์ฆ˜
    • Heap
    • Huffman Coding
    • Priority Queue
    • Bellman-Ford ์•Œ๊ณ ๋ฆฌ์ฆ˜
    • C++
      • Class
      • STL
        • STL pair
        • STL Container - Associate Container
        • STL Container - Sequence Container
        • STL Container - Container Adapter
  • JavaScript
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  1. Spring

Spring Singleton

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Spring์—์„œ์˜ singleton pattern์„ ์•Œ์•„๋ณด๊ธฐ ์ด์ „์—

๋ฅผ ์„ ํ–‰ํ•˜๋ฉด ๋” ์ดํ•ดํ•˜๋Š”๋ฐ ์ข‹๋‹ค.

Singleton Container

์Šคํ”„๋ง์€ ๊ธฐ๋ณธ์ ์œผ๋กœ ๋ณ„๋‹ค๋ฅธ ์„ค์ •์„ ํ•˜์ง€ ์•Š์œผ๋ฉด ๋‚ด๋ถ€์—์„œ ์ƒ์„ฑํ•˜๋Š” ๋นˆ ์˜ค๋ธŒ์ ํŠธ๋ฅผ ๋ชจ๋‘ ์‹ฑ๊ธ€ํ†ค์œผ๋กœ ๋งŒ๋“ ๋‹ค.

์Šคํ”„๋ง์€ ์„œ๋ฒ„ ํ™˜๊ฒฝ์—์„œ ์‹ฑ๊ธ€ํ†ค์ด ๋งŒ๋“ค์–ด์ ธ ์„œ๋น„์Šค ์˜ค๋ธŒ์ ํŠธ ๋ฐฉ์‹์œผ๋กœ ์‚ฌ์šฉ๋˜๋Š” ๊ฒƒ์€ ์ ๊ทน ์ง€์ง€ํ•œ๋‹ค. ํ•˜์ง€๋งŒ ์ž๋ฐ”์˜ ๊ธฐ๋ณธ์ ์ธ ์‹ฑ๊ธ€ํ†ค ํŒจํ„ด์˜ ๊ตฌํ˜„ ๋ฐฉ์‹์€ ์—ฌ๋Ÿฌ๊ฐ€์ง€ ๋‹จ์ ์ด ์žˆ๊ธฐ๋•Œ๋ฌธ์— ์Šคํ”„๋ง์€ ์ง์ ‘ ์‹ฑ๊ธ€ํ†ค ํ˜•ํƒœ์˜ ์˜ค๋ธŒ์ ํŠธ๋ฅผ ๋งŒ๋“ค๊ณ  ๊ด€๋ฆฌํ•˜๋Š” ๊ธฐ๋Šฅ์„ ์ œ๊ณตํ•œ๋‹ค.

์Šคํ”„๋ง ์ปจํ…Œ์ด๋„ˆ๋Š” ์‹ฑ๊ธ€ํ†ค ์ปจํ…Œ์ด๋„ˆ ์—ญํ• ์„ ํ•˜๋ฉฐ, ์ด๋ ‡๊ฒŒ ์‹ฑ๊ธ€ํ†ค ๊ฐ์ฒด๋ฅผ ์ƒ์„ฑํ•˜๊ณ  ๊ด€๋ฆฌํ•˜๋Š” ๊ธฐ๋Šฅ์„ Singleton Registry๋ผ๊ณ  ํ•œ๋‹ค.

Singleton Registry์˜ ์žฅ์ ์€ ํ‰๋ฒ”ํ•œ ์ž๋ฐ” ํด๋ž˜์Šค์ด๋”๋ผ๋„ IoC๋ฐฉ์‹์˜ ์ปจํ…Œ์ด๋„ˆ๋ฅผ ์‚ฌ์šฉํ•ด ์ƒ์„ฑ๊ณผ ๊ด€๊ณ„์„ค์ •, ์‚ฌ์šฉ ๋“ฑ์— ๋Œ€ํ•œ ์ œ์–ด๊ถŒ์„ ์†์‰ฝ๊ฒŒ ์‹ฑ๊ธ€ํ†ค ๋ฐฉ์‹์œผ๋กœ ๋งŒ๋“ค์–ด์ ธ ๊ด€๋ฆฌ๋˜๊ฒŒ ํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋ ‡๊ธฐ ๋•Œ๋ฌธ์— ํ…Œ์ŠคํŠธ ํ™˜๊ฒฝ์—์„œ๋„ ์ž์œ ๋กญ๊ฒŒ ์˜ค๋ธŒ์ ํŠธ๋ฅผ ๋งŒ๋“ค ์ˆ˜ ์žˆ๊ณ , ํ…Œ์ŠคํŠธ๋ฅผ ์œ„ํ•œ ๋ชฉ์ ์œผ๋กœ ์˜ค๋ธŒ์ ํŠธ๋ฅผ ๋Œ€์ฒดํ•˜๋Š” ๊ฒƒ๋„ ๊ฐ„๋‹จํ•˜๋‹ค.

์ฆ‰, ์‹ฑ๊ธ€ํ„ด ํŒจํ„ด์˜ ๋‹จ์ ์„ ํ•ด๊ฒฐํ•˜๋ฉด์„œ ๊ฐ์ฒด๋ฅผ ์‹ฑ๊ธ€ํ†ค ๋ฐฉ์‹์œผ๋กœ ์œ ์ง€ ํ•  ์ˆ˜ ์žˆ๋‹ค.

( 1. ์‹ฑ๊ธ€ํ†ค ํŒจํ„ด์„ ์œ„ํ•œ ์ง€์ €๋ถ„ํ•œ ์ฝ”๋“œ๊ฐ€ ์ถ”๊ฐ€๋˜์ง€ ์•Š์Œ. 2. DIP, OCP, ํ…Œ์ŠคํŠธ, private ์ƒ์„ฑ์ž๋กœ ๋ถ€ํ„ฐ ์ž์œ ๋กญ๊ฒŒ ์‹ฑ๊ธ€ํ†ค ์‚ฌ์šฉ ๊ฐ€๋Šฅ)

์‹ฑ๊ธ€ํ†ค์ด ๋ฉ€ํ‹ฐ์Šค๋ ˆ๋“œ ํ™˜๊ฒฝ์—์„œ ์„œ๋น„์Šค ํ˜•ํƒœ์˜ ์˜ค๋ธŒ์ ํŠธ๋กœ ์‚ฌ์šฉ๋˜๋Š” ๊ฒฝ์šฐ์—๋Š” stateless ๋ฐฉ์‹์œผ๋กœ ๋งŒ๋“ค์–ด์ ธ์•ผํ•œ๋‹ค. ์ด๋•Œ๋Š” ์ฝ๊ธฐ์ „์šฉ ๊ฐ’์ด๋ผ๋ฉด ์ดˆ๊ธฐํ™” ์‹œ์ ์— ์ธ์Šคํ„ด์Šค ๋ณ€์ˆ˜์— ์ €์žฅํ•ด๋‘๊ณ  ๊ณต์œ ํ•˜๋Š” ๊ฒƒ์€ ๋ฌธ์ œ ์—†๋‹ค. ๋งŒ์•ฝ ๊ฐ ์š”์ฒญ์— ๋Œ€ํ•œ ์ •๋ณด๋‚˜, DB ์„œ๋ฒ„์˜ ๋ฆฌ์†Œ์Šค๋กœ ๋ถ€ํ„ฐ ์ƒ์„ฑํ•œ ์ •๋ณด๋Š” ํŒŒ๋ผ๋ฏธํ„ฐ์™€ ๋กœ์ปฌ ๋ณ€์ˆ˜, ๋ฆฌํ„ด ๊ฐ’์„ ์ด์šฉํ•˜๋ฉด ๋œ๋‹ค. ๋ฉ”์†Œ๋“œ ํŒŒ๋ผ๋ฏธํ„ฐ๋‚˜, ๋ฉ”์†Œ๋“œ ์•ˆ์—์„œ ์ƒ์„ฑ๋˜๋Š” ๋กœ์ปฌ ๋ณ€์ˆ˜๋Š” ๋งค๋ฒˆ ์ƒˆ๋กœ์šด ๊ฐ’์„ ์ €์žฅํ•  ๋…๋ฆฝ์ ์ธ ๊ณต๊ฐ„์ด ๋งŒ๋“ค์–ด์ง€๊ธฐ ๋•Œ๋ฌธ์— ์‹ฑ๊ธ€ํ†ค์ด๋ผ๊ณ  ํ•ด๋„ ๋ฌธ์ œ์—†๋‹ค.

Spring์—์„œ์˜ Singleton Pattern

spring์˜ bean๋“ค์€ Bean Factory์— ์˜ํ•ด์„œ ๊ด€๋ฆฌ๋˜๊ณ  ์žˆ์œผ๋ฉฐ, ๊ธฐ๋ณธ์ ์œผ๋กœ ์ด๋Ÿฌํ•œ bean์˜ ์ƒ๋ช…์ฃผ๊ธฐ์˜ scope๋Š” singleton์„ ๋”ฐ๋ฅด๊ณ  ์žˆ๋‹ค. Spring Boot์—์„œ๋Š” ๋ณ„๋„์˜ ์„ค์ •์ด ์—†๋‹ค๋ฉด, DefaultListableBeanFactory๋ฅผ ๊ธฐ๋ณธ์œผ๋กœ ์‚ฌ์šฉํ•˜๋ฉฐ, resolveBean ๋ฉ”์†Œ๋“œ๋ฅผ ๋ณด๋ฉด ์•Œ ์ˆ˜ ์žˆ๋‹ค.

    @Nullable
    private <T> T resolveBean(ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) {
        // 1. ๋“ฑ๋ก๋˜์–ด์žˆ๋Š” bean๋“ค์˜ ์ด๋ฆ„์„ ๊ฒ€์ƒ‰
        NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args, nonUniqueAsNull);

        // 2. ๋“ฑ๋ก๋˜์–ด์žˆ๋‹ค๋ฉด ํ•ด๋‹น bean์„ ๋ฆฌํ„ด(์ธ์Šคํ„ด์Šค)
        if (namedBean != null) {
            return namedBean.getBeanInstance();
        }

        // 3. ๋‹ค๋ฅธ beanfactory์—์„œ ์š”์ฒญํ•œ bean ์ฐพ๊ธฐ    
        BeanFactory parent = getParentBeanFactory();
        if (parent instanceof DefaultListableBeanFactory) {
            return ((DefaultListableBeanFactory) parent).resolveBean(requiredType, args, nonUniqueAsNull);
        }
        else if (parent != null) {
            ObjectProvider<T> parentProvider = parent.getBeanProvider(requiredType);
            if (args != null) {
                return parentProvider.getObject(args);
            }
            else {
                return (nonUniqueAsNull ? parentProvider.getIfUnique() : parentProvider.getIfAvailable());
            }
        }
        // 4. ์ฐพ์ง€ ๋ชปํ–ˆ์„ ์‹œ null ๋ฐ˜ํ™˜
        return null;
    }

ํ•˜์ง€๋งŒ ์—ฌ๊ธฐ์—์„œ๋Š” private static ์ ‘๊ทผ ์ œ์–ด์ž๋ฅผ ํ†ตํ•œ singleton ํŒจํ„ด์€ ์ฐพ์•„๋ณผ ์ˆ˜ ์—†๋‹ค.

์•ˆํ‹ฐ ํŒจํ„ด

์•ˆํ‹ฐ ํŒจํ„ด์ด๋ž€, ์Šต๊ด€์ ์œผ๋กœ ๋งŽ์ด ์‚ฌ์šฉํ•˜๋Š” ํŒจํ„ด์ด์ง€๋งŒ ์„ฑ๋Šฅ, ๋””๋ฒ„๊น…, ์œ ์ง€๋ณด์ˆ˜, ๊ฐ€๋…์„ฑ ์ธก๋ฉด์—์„œ ๋ถ€์ •์ ์ธ ์˜ํ–ฅ์„ ์ค„ ์ˆ˜ ์žˆ์–ด ์ง€์–‘ํ•˜๋Š” ํŒจํ„ด์ด๋‹ค.

Singleton ํŒจํ„ด์€ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๋‹จ์ ์ด ์žˆ๋‹ค.

  1. private ์ƒ์„ฑ์ž๋ฅผ ๊ฐ€์ง€๊ณ  ์žˆ์–ด ์ƒ์†์„ ํ•  ์ˆ˜ ์—†๋‹ค.( ๋‹คํ˜•์„ฑ ์ œ๊ณต ๋ถˆ๊ฐ€๋Šฅ, ๊ฐ์ฒด์ง€ํ–ฅ ์„ค๊ณ„ ์ ์šฉ ๋ถˆ๊ฐ€)

  2. ํ…Œ์ŠคํŠธ๊ฐ€ ์–ด๋ ต๋‹ค.

  3. ์„œ๋ฒ„ํ™˜๊ฒฝ์—์„œ๋Š” 1๊ฐœ์˜ instance๋ฅผ ๋ณด์žฅํ•˜์ง€ ๋ชปํ•œ๋‹ค.

  4. ์ „์—ญ ์ƒํƒœ๋ฅผ ๋งŒ๋“ค ์ˆ˜ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ๋ฐ”๋žŒ์งํ•˜์ง€ ๋ชปํ•˜๋‹ค.

    • singleton์€ ์–ด๋””์—์„œ๋“ ์ง€ ๋ˆ„๊ตฌ๋‚˜ ์ ‘๊ทผํ•ด ์‚ฌ์šฉํ•  ์ˆ˜ ์žˆ์œผ๋ฏ€๋กœ, ๊ฐ์ฒด์ง€ํ–ฅ์—์„œ ๊ถŒ์žฅํ•˜์ง€ ๋˜์ง€ ์•Š๋Š” ํ”„๋กœ๊ทธ๋ž˜๋ฐ ๋ชจ๋ธ์ด๋‹ค.

์ด๋Ÿฌํ•œ ์ด์œ ๋กœ Spring์—์„œ ์ง์ ‘ ์‹ฑ๊ธ€ํ†ค ํŒจํ„ด์„ ์‚ฌ์šฉํ•˜์ง€ ์•Š์œผ๋ฉฐ, Singleton Registry ๋ฐฉ์‹์„ ์‚ฌ์šฉํ•œ๋‹ค.

Singleton Registry / Singleton Pattern ์ฃผ์˜์ 

๊ฐ์ฒด ์ธ์Šคํ„ด์Šค๋ฅผ ํ•˜๋‚˜๋งŒ ์ƒ์„ฑํ•ด์„œ ๊ณต์œ ํ•˜๋Š” ์‹ฑ๊ธ€ํ†ค ๋ฐฉ์‹์€ ์—ฌ๋Ÿฌ ํด๋ผ์ด์–ธํŠธ๊ฐ€ ํ•˜๋‚˜์˜ ๊ฐ™์€ ๊ฐ์ฒด ์ธ์Šคํ„ด์Šค๋ฅผ ๊ณต์œ ํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์‹ฑ๊ธ€ํ†ค ๊ฐ์ฒด๋Š” ์ƒํƒœ๋ฅผ ์œ ์ง€ (stateful)ํ•˜๊ฒŒ ์„ค๊ณ„ํ•˜๋ฉด ์•ˆ๋œ๋‹ค. ๋ฌด์ƒํƒœ(stateless)๋กœ ์„ค๊ณ„ํ•ด์•ผ ํ•œ๋‹ค!

  • ํŠน์ • ํด๋ผ์ด์–ธํŠธ์— ์˜์กด์ ์ธ ํ•„๋“œ๊ฐ€ ์žˆ์œผ๋ฉด ์•ˆ๋œ๋‹ค.

  • ํŠน์ • ํด๋ผ์ด์–ธํŠธ๊ฐ€ ๊ฐ’์„ ๋ณ€๊ฒฝํ•  ์ˆ˜ ์žˆ๋Š” ํ•„๋“œ๊ฐ€ ์žˆ์œผ๋ฉด ์•ˆ๋œ๋‹ค!

  • ๊ฐ€๊ธ‰์  ์ฝ๊ธฐ๋งŒ ๊ฐ€๋Šฅํ•ด์•ผ ํ•œ๋‹ค.

  • ํ•„๋“œ ๋Œ€์‹ ์— ์ž๋ฐ”์—์„œ ๊ณต์œ ๋˜์ง€ ์•Š๋Š”, ์ง€์—ญ๋ณ€์ˆ˜, ํŒŒ๋ผ๋ฏธํ„ฐ, ThreadLocal ๋“ฑ์„ ์‚ฌ์šฉํ•ด์•ผ ํ•œ๋‹ค.

์Šคํ”„๋ง ๋นˆ์˜ ํ•„๋“œ์— ๊ณต์œ  ๊ฐ’์„ ์„ค์ •ํ•˜๋ฉด ์ •๋ง ํฐ ์žฅ์• ๊ฐ€ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค.

@Configuration

/**
 * ์• ํ”Œ๋ฆฌ์ผ€์…˜์˜ ์‹ค์ œ ๋™์ž‘์— ํ•„์š”ํ•œ ๊ตฌํ˜„ ๊ฐ์ฒด ์ƒ์„ฑ
 * ์ƒ์„ฑํ•œ ๊ฐ์ฒด ์ธ์Šคํ„ด์Šค์˜ ์ฐธ์กฐ๋ฅผ ์ƒ์„ฑ์ž๋ฅผ ํ†ตํ•ด ์ฃผ์ž…ํ•ด์ค€๋‹ค.
 * @Configuration ์–ด๋…ธํ…Œ์ด์…˜์œผ๋กœ @Bean์ด ์‹ฑ๊ธ€ํ†ค์œผ๋กœ ๊ด€๋ฆฌ๋  ์ˆ˜ ์žˆ๊ฒŒ ํ•ด์ค€๋‹ค.
 */
@Configuration
public class AppConfig {

    @Bean
    public MemberService memberService() {
        System.out.println("call AppConfig.memberService");
        return new MemberServiceImpl(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {
        System.out.println("AppConfig.memberRepository");
        return new MemoryMemberRepository();
    }

    @Bean
    public OrderService orderService(){
        System.out.println("AppConfig.orderService");
        return new OrderServiceImpl(memberRepository(), getDiscountPolicy());
    }

    @Bean
    public DiscountPolicy getDiscountPolicy() {
        return new RateDiscountPolicy();
    }

}
package dh0023.springcore.singleton;

import dh0023.springcore.config.AppConfig;
import dh0023.springcore.member.repository.MemberRepository;
import dh0023.springcore.member.service.MemberServiceImpl;
import dh0023.springcore.order.service.OrderServiceImpl;
import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class ConfigurationSingletonTest {

    @Test
    void configurationTest() {
        ApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);

        MemberServiceImpl memberService = ac.getBean("memberService", MemberServiceImpl.class);
        OrderServiceImpl orderService = ac.getBean("orderService", OrderServiceImpl.class);
        MemberRepository memberRepository = ac.getBean("memberRepository", MemberRepository.class);

        MemberRepository memberRepository1 = memberService.getMemberRepository();
        MemberRepository memberRepository2 = orderService.getMemberRepository();

        System.out.println("memberRepository = " + memberRepository);
        System.out.println("memberRepository1 = " + memberRepository1);
        System.out.println("memberRepository2 = " + memberRepository2);

        Assertions.assertThat(memberRepository).isSameAs(memberRepository1);
        Assertions.assertThat(memberRepository).isSameAs(memberRepository2);
    }


    @Test
    void configurationDeep() {
        ApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);
        AppConfig bean = ac.getBean(AppConfig.class);

        System.out.println("bean = " + bean.getClass());
        // bean = class dh0023.springcore.config.AppConfig$$EnhancerBySpringCGLIB$$2a067523

    }
}

์ˆœ์ˆ˜ํ•œ ํด๋ž˜์Šค๋ผ๋ฉด class dh0023.springcore.config.AppConfig๋กœ ์ถœ๋ ฅ๋˜์–ด์•ผํ•œ๋‹ค. ํ•˜์ง€๋งŒ, @Configuration ์ด CGLIB ๋ฐ”์ดํŠธ ์ฝ”๋“œ ์กฐ์ž‘ ๋ผ์ด๋ธŒ๋Ÿฌ๋ฆฌ๋ฅผ ์‚ฌ์šฉํ•ด AppConfig ๋ฅผ ์ƒ์†๋ฐ›์€ ์ž„์˜์˜ ํด๋ž˜์Šค(AppConfig@CGLIB)๋ฅผ ์Šคํ”„๋ง ๋นˆ์œผ๋กœ ๋“ฑ๋กํ•œ๋‹ค.

@Bean์ด ๋ถ™์€ ๋ฉ”์„œ๋“œ๋งˆ๋‹ค ์ด๋ฏธ ์Šคํ”„๋ง ๋นˆ์ด ์กด์žฌํ•œ๋‹ค๋ฉด, ์กด์žฌํ•˜๋Š” ๋นˆ์„ ๋ฐ˜ํ™˜ํ•˜๊ณ , ์กด์žฌํ•˜์ง€ ์•Š๋Š”๋‹ค๋ฉด ์ƒˆ๋กœ ์ƒ์„ฑํ•˜๋Š” ๋กœ์ง์ด ํฌํ•จ๋˜์–ด ์žˆ์„ ๊ฒƒ์œผ๋กœ ์˜ˆ์ƒ๋œ๋‹ค.

๋งŒ์•ฝ @Configuration ์„ ์„ค์ •ํ•˜์ง€ ์•Š๊ณ  @Bean ๋นˆ์„ ๋“ฑ๋กํ•˜๋ฉด ์–ด๋–ป๊ฒŒ ๋ ๊นŒ?

/**
 * ์• ํ”Œ๋ฆฌ์ผ€์…˜์˜ ์‹ค์ œ ๋™์ž‘์— ํ•„์š”ํ•œ ๊ตฌํ˜„ ๊ฐ์ฒด ์ƒ์„ฑ
 * ์ƒ์„ฑํ•œ ๊ฐ์ฒด ์ธ์Šคํ„ด์Šค์˜ ์ฐธ์กฐ๋ฅผ ์ƒ์„ฑ์ž๋ฅผ ํ†ตํ•ด ์ฃผ์ž…ํ•ด์ค€๋‹ค.
 * @Configuration ์–ด๋…ธํ…Œ์ด์…˜์œผ๋กœ @Bean์ด ์‹ฑ๊ธ€ํ†ค์œผ๋กœ ๊ด€๋ฆฌ๋  ์ˆ˜ ์žˆ๊ฒŒ ํ•ด์ค€๋‹ค.
 */
public class AppConfig {

    @Bean
    public MemberService memberService() {
        System.out.println("call AppConfig.memberService");
        return new MemberServiceImpl(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {
        System.out.println("AppConfig.memberRepository");
        return new MemoryMemberRepository();
    }

    @Bean
    public OrderService orderService(){
        System.out.println("AppConfig.orderService");
        return new OrderServiceImpl(memberRepository(), getDiscountPolicy());
    }

    @Bean
    public DiscountPolicy getDiscountPolicy() {
        return new RateDiscountPolicy();
    }

}
package dh0023.springcore.singleton;

import dh0023.springcore.config.AppConfig;
import dh0023.springcore.member.repository.MemberRepository;
import dh0023.springcore.member.service.MemberServiceImpl;
import dh0023.springcore.order.service.OrderServiceImpl;
import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class ConfigurationSingletonTest {

    @Test
    void configurationTest() {
        ApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);

        MemberServiceImpl memberService = ac.getBean("memberService", MemberServiceImpl.class);
        OrderServiceImpl orderService = ac.getBean("orderService", OrderServiceImpl.class);
        MemberRepository memberRepository = ac.getBean("memberRepository", MemberRepository.class);

        MemberRepository memberRepository1 = memberService.getMemberRepository();
        MemberRepository memberRepository2 = orderService.getMemberRepository();

        System.out.println("memberRepository = " + memberRepository);
        System.out.println("memberRepository1 = " + memberRepository1);
        System.out.println("memberRepository2 = " + memberRepository2);

        Assertions.assertThat(memberRepository).isSameAs(memberRepository1);
        Assertions.assertThat(memberRepository).isSameAs(memberRepository2);
    }


    @Test
    void configurationDeep() {
        ApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);
        AppConfig bean = ac.getBean(AppConfig.class);

        System.out.println("bean = " + bean.getClass());
        // bean = class dh0023.springcore.config.AppConfig

    }
}

@Configuration์„ ๋“ฑ๋กํ•˜์ง€ ์•Š์•„๋„, @Bean์œผ๋กœ ์Šคํ”„๋ง ๋นˆ๋“ฑ๋ก์ด ๊ฐ€๋Šฅํ•˜๋‚˜, ๋ฐ”์ดํŠธ ์กฐ์ž‘์„ ํ•˜์ง€ ์•Š๋Š” Class๊ฐ€ ์ƒ์„ฑ๋œ๋‹ค. ๋˜ํ•œ, ์‹ฑ๊ธ€ํ†ค์ด ๋ณด์žฅ๋˜์ง€ ์•Š๋Š”๋‹ค.

์ฐธ๊ณ 

Singleton ๋””์ž์ธํŒจํ„ด
Item3 - Singleton
https://sabarada.tistory.com/25
๊น€์˜ํ•œ ์Šคํ”„๋ง ํ•ต์‹ฌ ์›๋ฆฌ - ๊ธฐ๋ณธํŽธ