Doctrine, Object Persistence, and You

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DOCTRINE, OBJECT PERSISTENCE, AND YOU Jeremy Mikola jmikola

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Agenda Design Patterns Object Persistence Behind the Persistence

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PEAR DB Metabase PEAR MDB PEAR MDB2 Zend_Db Doctrine ORM 1.x Doctrine ORM 2.x Doctrine DBAL

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Design Patterns

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Who needs design patterns?

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Selecting Data from a Table $ c o n = m y s q l i _ c o n n e c t ( " e x a m p l e . c o m " , " p e t e r " , " a b c 1 2 3 " , " m y _ d b " ) ; i f ( m y s q l i _ c o n n e c t _ e r r n o ( ) ) { e c h o " F a i l e d t o c o n n e c t t o M y S Q L : " . m y s q l i _ c o n n e c t _ e r r o r ( ) ; } $ r e s u l t = m y s q l i _ q u e r y ( $ c o n , " S E L E C T * F R O M P e r s o n s " ) ; w h i l e ( $ r o w = m y s q l i _ f e t c h _ a r r a y ( $ r e s u l t ) ) { e c h o $ r o w [ ' F i r s t N a m e ' ] . " " . $ r o w [ ' L a s t N a m e ' ] ; e c h o " < b r > " ; } m y s q l i _ c l o s e ( $ c o n ) ; http://www.w3schools.com/php/php_mysql_select.asp

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Inserting Form Data into a Database $ c o n = m y s q l i _ c o n n e c t ( " e x a m p l e . c o m " , " p e t e r " , " a b c 1 2 3 " , " m y _ d b " ) ; i f ( m y s q l i _ c o n n e c t _ e r r n o ( ) ) { e c h o " F a i l e d t o c o n n e c t t o M y S Q L : " . m y s q l i _ c o n n e c t _ e r r o r ( ) ; } $ s q l = " I N S E R T I N T O P e r s o n s ( F i r s t N a m e , L a s t N a m e , A g e ) V A L U E S ( ' $ _ P O S T [ f i r s t n a m e ] ' , ' $ _ P O S T [ l a s t n a m e ] ' , ' $ _ P O S T [ a g e ] ' ) " ; i f ( ! m y s q l i _ q u e r y ( $ c o n , $ s q l ) ) { d i e ( ' E r r o r : ' . m y s q l i _ e r r o r ( $ c o n ) ) ; } m y s q l i _ c l o s e ( $ c o n ) ; http://www.w3schools.com/php/php_mysql_insert.asp

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Data Source Architectural Patterns Table data gateway Row data gateway Active record Data mapper

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Gateway Patterns

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An object that encapsulates access to an external system or resource. “ — Martin Fowler in PoEAA

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Table Data Gateway e.g. Zend\Db\TableGateway

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An object that acts as a Gateway to a database table. One instance handles all the rows in the table. “ — Martin Fowler in PoEAA

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Table Data Gateway

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What this looks like in PHP n a m e s p a c e Z e n d \ D b \ T a b l e G a t e w a y ; i n t e r f a c e T a b l e G a t e w a y I n t e r f a c e { p u b l i c f u n c t i o n g e t T a b l e ( ) ; p u b l i c f u n c t i o n s e l e c t ( $ w h e r e = n u l l ) ; p u b l i c f u n c t i o n i n s e r t ( $ s e t ) ; p u b l i c f u n c t i o n u p d a t e ( $ s e t , $ w h e r e = n u l l ) ; p u b l i c f u n c t i o n d e l e t e ( $ w h e r e ) ; }

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Row Data Gateway e.g. Zend\Db\RowGateway

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Row Data Gateway

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What’s the problem? Gateways are thin abstractions Data model not included Hydration and persistence?

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Active Record e.g. Doctrine ORM 1.x

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An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data. “ — Martin Fowler in PoEAA

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Active Record

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Active Record Sits on top of our domain model Row data gateway + business logic

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Domain Model Data encapsulation Business logic Relationships Validation?

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Active Record adds… Factory method for new objects Hydration for fetched objects Persistence logic Common queries CRUD methods

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What this looks like in PHP / / c r e a t e T i t o $ u s e r = U s e r : : c r e a t e ( [ ' n a m e ' = > ' T i t o ' , ' s t a t e ' = > ' V A ' ] ) ; / / r e a d T i t o $ u s e r = U s e r : : f i n d _ b y _ n a m e ( ' T i t o ' ) ; / / u p d a t e T i t o $ u s e r - > n a m e = ' T i t o J r ' ; $ u s e r - > s a v e ( ) ; / / d e l e t e T i t o $ u s e r - > d e l e t e ( ) ; http://phpactiverecord.org/projects/main/wiki/Quick_Start

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What’s the problem? Testability Single Responsibility Principle

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ONE DOES NOT SIMPLY MOCK OUT ACTIVERECORD

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What’s the problem? Testability Scalability and performance Single Responsibility Principle Multitenancy

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Scalability and Performance Fat models eat memory

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An Elephant Never Forgets

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Data Mapper e.g. Doctrine ORM 2.x, ODMs

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A layer of Mappers that moves data between objects and a database while keeping them independent of each other and the mapper itself. “ — Martin Fowler in PoEAA

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Data Mapper

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Data Mapper Complements the domain model, instead of augmenting it Manages hydration and persistence

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The Data Mapper is a layer of software that separates the in-memory objects from the database. “ — Martin Fowler in PoEAA

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☑ Separation of concerns

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With Data Mapper the in-memory objects needn’t know even that there’s a database present. “ — Martin Fowler in PoEAA

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☑ Testability

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What this looks like in PHP / / c r e a t e J o n $ u s e r = n e w U s e r ( ) ; $ u s e r - > s e t N a m e ( ' J o n ' ) ; $ u s e r - > s e t S t a t e ( ' T N ' ) ; $ m a n a g e r - > p e r s i s t ( $ u s e r ) ; $ m a n a g e r - > f l u s h ( ) ; / / r e a d J o n $ u s e r = $ m a n a g e r - > g e t R e p o s i t o r y ( ' U s e r ' ) - > f i n d O n e B y ( [ ' n a m e ' = > ' J o n ' ] ) ; / / u p d a t e J o n $ u s e r - > s e t N a m e ( ' J o n W a g e ' ) ; $ m a n a g e r - > f l u s h ( ) ; / / d e l e t e J o n $ m a n a g e r - > r e m o v e ( $ u s e r ) ; $ m a n a g e r - > f l u s h ( ) ; http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/tutorials/getting-started.html

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Data Mapper Simple models Manager handles persistence Repository holds queries

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☑ Multitenancy

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☑ Scalability and performance

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Object Persistence in Doctrine ORM 2.x, ODMs Inspired by and Hibernate JPA 2.0

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Architecture EventManager Metadata Hydrator Persister UnitOfWork ObjectManager Repository Query

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Metadata / * * * @ E n t i t y * @ T a b l e ( n a m e = " p r o d u c t s " ) * / c l a s s P r o d u c t { / * * * @ I d * @ C o l u m n ( t y p e = " i n t e g e r " ) * @ G e n e r a t e d V a l u e * / p r o t e c t e d $ i d ; / * * @ C o l u m n ( t y p e = " s t r i n g " ) * / p r o t e c t e d $ n a m e ; / / . . . }

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Hydrator

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Persister

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Unit of Work

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A Unit of Work keeps track of everything you do during a business transaction that can affect the database. “ — Martin Fowler in PoEAA

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When you’re done, it figures out everything that needs to be done to alter the database as a result of your work. “ — Martin Fowler in PoEAA

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Unit of Work: Object States New Managed Removed Detached

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What this looks like in PHP $ u s e r = n e w U s e r ( ) ; $ u s e r - > s e t N a m e ( ' J o n ' ) ; / / $ u s e r i s N E W $ m a n a g e r - > p e r s i s t ( $ u s e r ) ; / / $ u s e r i s M A N A G E D $ m a n a g e r - > f l u s h ( ) ; $ m a n a g e r - > r e m o v e ( $ u s e r ) ; / / $ u s e r i s R E M O V E D $ m a n a g e r - > f l u s h ( ) ;

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Unit of Work: Identity Map

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What this looks like in PHP $ u s e r A = $ m a n a g e r - > g e t R e p o s i t o r y ( ' U s e r ' ) - > f i n d O n e B y ( [ ' i d ' = > 1 ] ) ; $ u s e r B = $ m a n a g e r - > g e t R e p o s i t o r y ( ' U s e r ' ) - > f i n d O n e B y ( [ ' i d ' = > 1 ] ) ; $ u s e r A = = = $ u s e r B ; / / t r u e

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Doctrine\Common\Persistence\ ObjectManager f i n d ( $ c l a s s , $ i d ) p e r s i s t ( $ o b j e c t ) r e m o v e ( $ o b j e c t ) f l u s h ( ) c l e a r ( ) d e t a c h ( $ o b j e c t ) m e r g e ( $ o b j e c t ) r e f r e s h ( $ o b j e c t )

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Lifecycle Events Remove Persist Update Load Flush Clear

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Event Notification

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Doctrine\Common\ EventManager d i s p a t c h E v e n t ( $ e v e n t , $ a r g s ) g e t L i s t e n e r s ( $ e v e n t ) h a s L i s t e n e r s ( $ e v e n t ) a d d E v e n t L i s t e n e r ( $ e v e n t , $ l i s t e n e r ) r e m o v e E v e n t L i s t e n e r ( $ e v e n t , $ l i s t e n e r ) a d d E v e n t S u b s c r i b e r ( $ s u b s c r i b e r ) r e m o v e E v e n t S u b s c r i b e r ( $ s u b s c r i b e r )

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Doctrine\Common\Persistence\ ObjectRepository f i n d ( $ i d ) f i n d A l l ( ) f i n d B y ( $ c r i t e r i a , … ) f i n d O n e B y ( $ c r i t e r i a ) g e t C l a s s N a m e ( )

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Query Abstracts database query API Fluent builder interface Filter classes ORM/ODM behavior e.g. hydration, fetch mode

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What this looks like in PHP / / $ q b i s a D o c t r i n e \ O R M \ Q u e r y B u i l d e r $ q b - > s e l e c t ( ' u ' ) - > f r o m ( ' U s e r ' , ' u ' ) - > w h e r e ( ' u . n a m e = : n a m e O R u . n i c k n a m e = : n a m e ' ) - > o r d e r B y ( ' u . a g e ' , ' D E S C ' ) - > s e t P a r a m e t e r s ( [ ' n a m e ' = > ' J o n ' ] ) - > g e t Q u e r y ( ) - > g e t R e s u l t ( )

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What this looks like in PHP / / $ q b i s a D o c t r i n e \ O R M \ Q u e r y B u i l d e r $ q b - > s e l e c t ( ' u ' ) - > f r o m ( ' U s e r ' , ' u ' ) - > w h e r e ( $ q b - > e x p r ( ) - > o r X ( $ q b - > e x p r ( ) - > e q ( ' u . n a m e ' , ' : n a m e ' ) , $ q b - > e x p r ( ) - > l i k e ( ' u . n i c k n a m e ' , ' : n a m e ' ) ) ) - > o r d e r B y ( ' u . a g e ' , ' D E S C ' ) - > s e t P a r a m e t e r s ( [ ' n a m e ' = > ' J o n ' ] ) - > g e t Q u e r y ( ) - > g e t R e s u l t ( ) ;

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Performance and Tunability Caching results, queries, etc. Change tracking policies Proxy objects, fetch modes Code generation

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Behind the Persistence

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Packages Cache Annotations Lexer Collections Inflector Common DBAL MongoDB CouchDB ORM MongoDB ODM CouchDB ODM PHPCR ODM

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packagist.org/packages/doctrine/

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Doctrine\Common\ Cache Supports over a dozen backends Namespaces and versioning Very simple API

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Doctrine\Common\ Annotations DocBlock annotation parsing Utilizes the lexer component Cache integration

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Doctrine\Common\ Collections Object-oriented collection interface ArrayCollection implementation ORM/ODM persistent collections Java-inspired Criteria API

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Doctrine\ DBAL Thin layer atop PDO SQL database abstraction Type mapping Query builder

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Doctrine\ MongoDB MongoDB driver abstraction Error handling, recovery Syntactic sugar Query builder

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But wait, there’s more! CouchDB client and ODM PHP Content Repository ODM OrientDB ODM Database migrations

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Wrapping Up

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Essentially the ORM can handle about 80- 90% of the mapping problems, but that last chunk always needs careful work by somebody who really understands how a relational database works. “ — Martin Fowler in OrmHate

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Pertinent Resources http://github.com/doctrine http://doctrine-project.org/ http://doctrine-project.org/jira

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Freenode IRC #doctrine #doctrine-dev

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THANKS! Questions?

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Image Credits by http://xkcd.com/327/ http://hqwallbase.com/images/big/Trees-Wallpaper-3008x2000.jpg http://www.angryarchitect.com/wp-content/uploads/2010/04/FowlerFront.jpg https://raw.github.com/paulirish/w3fools/master/images/pity.jpg http://b-i.forbesimg.com/danschawbel/files/2013/03/david.heinemeier.hansson.jpg http://icons8.com http://www.visualpharm.com/