How to Choose
the ORM on Android
DroidKaigi 2017, day 2, 10:40-11:30 room 3
by goro-fuji@bitjourney.com (@__gfx__)
#DroidKaigi3
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Table of Contents
I. Introduction to the Speaker
II. What ORMs Are
III. Comparison of ORMs
IV. How Orma Is Designed
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Table of Contents
I. Introduction to the Speaker
II. What ORMs Are
III. Comparison of ORMs
IV. How Orma Is Designed
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Introduction to the Speaker
• Rails Engineer at Bit Jouryney, Inc.
• Released Kibela (kibe.la) recently
• Mobile Application Engineer at Speee, Inc.
• As a Technical Advisor
• Loves Programming, Cooking and Gaming
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Released Kibela at 2017/3/1
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Table of Contents
I. Introduction to the Speaker
II. What ORMs Are
III. Comparison of ORMs
IV. How Orma Is Designed
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Why You Stores Data to Local
• To identify the device and its preferences
• Much faster than Web API
• Much more reliable than Web API
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Why You Stores Data to Local
• To identify the device and its preferences
• Much faster than Web API
-> cache
• Much more reliable than Web API
-> offline-first development
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What You Stores to Storages
• Preferences (or settings)
• Caches
• Drafts
• Buffers (or queue)
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Data Storage on Android
• Built-in SharedPreferences
• Built-in File with the filesystem
• Built-in SQLiteDatabase (SQLite)
• SQLite wrappers (ORMs)
• Original DB (Realm, ObjectBox, etc.)
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Data Storage on Android
• Built-in SharedPreferences
• Built-in File with the filesystem
• Built-in SQLiteDatabase (SQLite)
• SQLite wrappers (ORMs)
• Original DB (Realm, ObjectBox, etc.)
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Built-in SQLiteDatabase
• RDBMS
• Interface to SQLite3 (C library)
• Opetations with SQL (SQL-92)
• Transactions
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ORMs
• Object-Relation Mapper
• Lots of implementations:
• ActiveAndroid, DBFlow, Orma,
Requery, ORMLite, greenDAO,
SugarORM, StorIO, Realm, and etc.
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What ORMs do
• O/R Mapping
• Query Builder
• Association Management
• Publish / Subscribe (pub-sub)
• Migration
Association (or relathinship)
• Handles table-to-table association
• has-one / has-many / many-to-many
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Pub-Sub
• Notifications on data-set changes
• Used to synchronize model state
• e.g. the state of “” over fragments
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Migration
• How schema changes apply to the
database
• Calling ALTER TABLE, or completely re-
create tables if needed
• SQLiteOpenHelper’s / Java code /
Automatic
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What are ORMs?
✅ O/R Mapping
✅ Query Builder
✅ Associations
✅ Publish / Subscribe (pub-sub)
✅ Migration
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As Open Source Software
• README / document
• CI / CD
• Number of comitters
• Changelogs / relase notes
• Recent activities
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Table of Contents
I. Introduction to the Speaker
II. What ORMs Are
III.Comparison of ORMs
IV. How Orma Is Designed
What to See
A. How O/R Mapping Is
B. The Interface of Query Builder
C. Association Support
D. Pub-Sub Support
E. Migration
F. Performance
G. As Open Source Software
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ActiveAndroid v3.0
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ActiveAndroid
• One of the most famous ORM in Android
• Considered as easy to use
• No longer maintained
• Baseline for many of ORMs
• Based on reflection
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Model Definition
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Usage
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Usage
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Usage
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Query Builder
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Association
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Association
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Has-Many Association
getMany() is useless because it returns List
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Pub-Sub: via ContentProvider
The end of Model#save() method:
↓
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Migration
• In short: TERRIBLE
• Just execute versioned SQL files
• In development: you have to
uninstall the app for each time you
change the schema
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As Open Source Software
• Last commit: 2014/10
• The last stable version tag: 2012/01
• No longer maintained
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Pros. and Cons.
•
Easy to setup / model / use
•
Not type safe
•
No longer maintained
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greenDAO v3.2.0
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greenDAO
• One of the most famous ORM in Android
• Considered as high performance
• Modeling was considered terrible
• Based on gradle-plugin-based code
generator
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Model Definition
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Model Definition (after sync)
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Usage
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Usage
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Usage
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Query Builder
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Query Builder
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Query Builder
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Association
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Pub-Sub
• Not supported
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Migration
• Not supported
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As Open Source Software
• Last commit: 2017/03
• Last stable release: 2016/10
• @greenbot is developing another ORM:
• ObjectBox, a brand-new mobile
database with source-code compatibility
with greenDAO
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Pros. and Cons.
•
Performance is awesome
•
Modifying source code seems
really strange
• Not so type safety
•
Migration is terrible
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Requery v1.2.0
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Requery
• a brand-new ORM for Android
• v1.0.0 is released at 2016/09
• Annotation-processor-based code
generator
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Model Definition
↓
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Usage
• DatabaseSouce extends SQLiteOpenHelper
• Models is a generated class
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Usage
• DatabaseSouce extends SQLiteOpenHelper
• Models is a generated class
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Usage
• DatabaseSouce extends SQLiteOpenHelper
• Models is a generated class
Migration
• Add new columns automatically
• but need schemaVersion++
• Do nothing if constraints or the type
change
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As Open Source Software
• Very active
• Not so kind for Android developers
• because it supports lots of
databases
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Pros. and Cons.
•
RxJava support seems cool
•
Too many abstraction
•
Supporting non-Android
plarfotms are useless for us
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SQLBright v0.6.2
&
SQLDelight v0.6.0
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SQLBrite & SQLDelight
• Developed by Square
• SQLBrite: pub-sub helper to SQLite
• SQLDelgith: generates models from
DSL
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SQLDelgiht DSL
That’s SQL
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SQLDelgiht DSL
That’s SQL
!?
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Pros. and Cons.
•
SQLBright is interesting if you
use raw SQLiteOpenHelper
•
SQLDelight’s DSL is strange
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Realm v3.0.0
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Realm (realm-java)
• A superstar of ORMs
• Not based on SQLite
• Developed by Realm
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Model Definition
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Usage
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Query Builder
• equalTo() is not type-safe
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Association
• Supported
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Pub-Sub
• Supported
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Migration
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Migration
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Realm Mobile Platform
• Synchronized data within multiple
devices
• See “Offline-First Application
Development” in DroidKaigi 217
day 1 by zaki50
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Pros. and Cons.
•
Users do not use generated classes,
and thus the interface is not type safe
•
Full-time comitters are awesome
•
Migration is terrible
•
Query builder is not type safe
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Table of Contents
I. Introduction to the Speaker
II. What ORMs are
III. Comparison of ORMs
IV. How Orma Is Designed
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Orma v4.2.1
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Orma
• v1.0.0 is released at 2016/01
• Used in cookpad, Abema TV,
mercari atte, pairs, droidkaigi 2017
• annotation-processor based code
generator
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Model Definition
• No base class
• Explicit annotations required
Query Builder
• Todo_Selector (generated class)
• Todo_Selector#idEq(long)
• only for indexed columns
• Todo_Selector#orderByIdDesc()
• only for indexed columns
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Generated Code
↓ jump to definition
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Association
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Pu-Sub
• Supported experimentally
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Migration
• schema-diff migration
• ALTER TABLE from diff
• step-by-step migration
• hand-written steps