Spring By Example One Day Workshop

Spring By Example
Oleksiy Rezchykov
Eugene Scripnik

About us
 Software Engineers

 Working with Spring since 2006

 Pragmatic programmers

 SpringByExample.com.ua
founders

SpringByExample.com.ua
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Contents
 Intro

 IoC using Spring

 Persistence with Spring

 Web applications with Spring MVC

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Intro
 What we will do today?

 Meet some new faces

 Learn some new stuff

 Code some new stuff

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SpringFramework
history
 In October 2002 Rod Johnson
wrote his famous book

 The first milestone release 1.0 -
June 2004

 Company renamed from
Interface21 to SpringSource in
2007

 SpringSource acquired by
VMWare in 2009

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Spring in 2012

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IoC using Spring
 Buiding xml contexts

 Bean scopes & lifecycles

 Constructor vs Setter injection

 Property placeholders

 p & c and util name spaces

 Annotation context

 Using component scan

 AOP usage

 Spring AOP vs AspectJ

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Inversion of Control
 Inversion of regular approach where object was
responsible for satisfying it’s own dependencies

 Implementation of Dependency Injection

 Container instantiates and wires dependencies

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IoC
 Pros vs Cons (to discuss)

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Injection types
 Setter injection– when you are using setter to fulfill
bean dependency

 Constructor injection – when constructor is called to
set-up a bean with dependencies

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CI vs SI
 Pro vs Cons (to discuss)

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Context
 An object which contains beans declarations with
their dependencies

 BeanFactory interface implementation

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XML namespaces

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Context

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Context usage

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Bean lifecycle
 Depends on scope and lazy initialization

 Main bean scopes:

Singleton and Prototype

(Also there are multiple web scopes)

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Bean instantiation order

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Bean Post-processing
• Bean instantiated for singletons with
Bean
instantiation
eager initialization

Dependency
• Dependencies are injected into beans
injection

• Bean post-processing actions
Bean post-
processing
• You can put your custom logic in here

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Property Editors

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Multiple config files

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Bean definition
inheritance

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Inner Beans

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Factory Method

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Map, List, Set, Prop,
Null

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Map, List, Set, Prop, Nul
l

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Util namespace

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Component model

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@Autowired
 Spring proprietary annotation for property injection

 Supports @Qualifier to select implementation by
name if more than one exists in context

 Has required parameter to enforce dependency
loading

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@Autowired

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@Inject
 Context and Dependency Injection (CDI) standard
JSR-299

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@Resource
 JSR 250 (Common annotations)

 Supports @PostConstruct and @PreDestroy as
well

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Autowiring
An appropriate bean for dependency is found through:

 Type

 Name

 Type and Name combination

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Resource loading and
i18n

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Resource loading and
i18n

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SpEl
 Stands for Spring Expression Language

 Can be used in the xml context

 Can be used in bean classes

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SpEl

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Java Spring Config
 @Configuration

 @Bean

 Support for Environment and Profiles

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Java Spring Config

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Environment abstraction
& context profiles
 Environment abstraction introduced in Spring 3.1

 Can be declaratively and programmatically
configured

 Affects property resolution

 Affects bean profiles

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& context profiles

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& context profiles

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AOP
A programming paradigm which allows to separate
cross-cutting concerns

Cross-cutting logic:

 Logging

 Tracing

 Security

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AOP
 Aspect

 Advice

 Join point

 Pointcut

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AOP

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Spring AOP
 Spring AOP defaults to using standard J2SE
dynamic proxies for AOP proxies. This enables any
interface (or set of interfaces) to be proxied.

 Spring AOP can also use CGLIB proxies. This is
necessary to proxy classes, rather than interfaces

 It is good practice to program to interfaces rather
than classes, business classes normally will
implement one or more business interfaces.

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AspectJ
 Spring AOP is often uses the AspectJ declaration
style
 AspectJ itself uses Load Time Weaving (LTW) to
modify the bean code according to Aspect logic
 LTW could do much more than dynamic proxies but it
is more time-consuming operation. This means that
LTW has a performance drawback.

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Persistence with Spring
 Building DAO

 Embedded Datasources

 JDBC vs ORM DAO’s

 Integration testing with Spring

 @Transactional & transactions with Spring

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Spring supports
 JDBC

 JPA

 JDO

 Concrete ORM

 NoSQL templates (Mongo/Redis)

 Graph DB abstractions - Spring Data Graph project

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Persistence layer
• Persistence service which has domain specific logic
Service

• Spring JDBCTemplate
• SessionFactory, EntityManagerFactory
Repository
(DAO) • Redis/Mongo template

• RDBMS (or NoSQL)
DB

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JDBCTemplate
 Useful interface

 No boilerplate code

 Exception handling

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JDBCTemplate

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JDBC namespace

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Intro to Hibernate
Object Relational Mapping - is a programming
technique for converting data between incompatible
type systems in object-oriented programming
languages. This creates, in effect, a "virtual object
database" that can be used from within the
programming language.

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ORM main challenges
 Object inheritance

 Object relations

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Hibernate main parts
 SessionFactory

 Session

 Entity

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Transactions in Spring
 Support for ACID transactions

 Declarative and programmatic

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Transaction managers
 Spring support both container managed and
framework managed transactions

Managers:

 DataSourceTransactionManager

 HibernateTransactionManager

 JPATransactionManager

 JTATransactionManager

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@Transactional
 Isolation levels

 Transaction propagation

 Read-only transactions

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Read-only transactions
 A read-only transaction can be used when your
code reads but does not modify data. Read-only
transactions can be a useful optimization in some
cases, such as when you are using Hibernate.

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Isolation levels
 DEFAULT - The default isolation level for the
underlying resource (usually this is the
READ_COMMITTED isolation level)

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Isolation levels
 READ_UNCOMMITTED - Least restrictive isolation
level. A transaction can read data updates even if
they haven't yet been committed. (The updates
might subsequently be rolled-back).

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Isolation levels
 READ_COMMITTED - A transaction can only read
data that has already been committed. The
transaction doesn't see uncommitted updates.

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Isolation levels
 REPEATABLE_READ - A transaction always reads
the same value after it has read some data. Other
transactions can update the data in parallel with the
original transaction.

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Isolation levels
 SERIALIZABLE - This is the most restrictive
isolation level. Transactions are completely isolated
from each other. Resource managers frequently
implement this isolation level by locking large
amounts of data

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Propagation
 NOT_SUPPORTED

Suspends client's transaction until bean method is complete

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Propagation
 SUPPORTS

If client has transaction, bean method is included in it

If client doesn't have transaction, bean method doesn't
create one

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Propagation
 REQUIRED

If client has a transaction, bean method is included in it

If client doesn't have a transaction, bean method creates
one

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Propagation
 REQUIRES_NEW

If client has a transaction, bean method creates new one
anyway

If client doesn't have a transaction, bean method creates
one

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Propagation
 MANDATORY

If client has a transaction, bean method uses it

If client doesn't have a transaction, exception!

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Propagation
 NEVER

If client has a transaction, exception!

If client doesn't have transaction, bean method doesn't
create one

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Persistence layer testing
 Context loading in test

 Environment abstraction and profiles usage

 Transactional methods

 Embedded data source could be used

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Persistence layer testing

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Spring MVC
 Application context

 Dispatcher Servlet and it’s context

 Controllers and mappings

 Implementing CRUD logic

 Using Spring for UI tests

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Application & Dispatcher
servlet context

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Front controller and
MVC

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URL mappings
 @RequestMapping

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View resolvers
 AbstractCachingViewResolver

 XmlViewResolver

 ResourceBundleViewResolver

 UrlBasedViewResolver

 InternalResourceViewResolver

 VelocityViewResolver / FreeMarkerViewResolver

 ContentNegotiatingViewResolver
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View resolvers

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CRUD in one place

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Using Spring for UI tests
 Integration testing of Controllers

 Spring as a framework for Selenium UI tests

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