The Spring FrameworkTM

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The Spring FrameworkTM
Rod Johnson Interface21
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Spring framework goals

• Make J2EE easier to use
• Address end-to-end requirements rather than one
  tier
• Eliminate need for middle tier glue
• Provide the best Inversion of Control solution
• Provide a pure Java AOP implementation, focused
  on solving common problems in J2EE
• Fully portable across application servers
• Core container can run in any environment, not
  only a server
• Works well in WebSphere

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Spring framework goals

• Non-invasive framework
• Application code has minimal or no dependency on
  Spring APIs
• Key principal seen throughout Springs design
• More power to the POJO
• Facilitate unit testing
• Allow effective TDD
• Allow business objects to be unit tested outside
  the container
• Facilitate OO best practice
• Were used to implementing EJB or J2EE
  applications rather than OO applications.
• It doesnt have to be this way.
• Provide a good alternative to EJB for many
  applications
• Enhance productivity compared to traditional
  J2EE approaches

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Part of a new wave of frameworks

• Big change in how J2EE applications are written
• Less emphasis on EJB
• EJB has been overused Often not appropriate
• Not just Spring PicoContainer, HiveMind and
  other Inversion of Control frameworks
• EJB 3.0 (2005) programming model looks a lot like
  
• (Spring IoC features) Hibernate
• EJB still has some unique capabilities for a
  minority of apps (distributed transaction
  management, RMI remoting)
• These lightweight frameworks are different
• Spring is the most mature, most powerful and most
  popular

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Unique Spring capabilities

• Declarative transaction management for POJOs with
  or without EJB
• Consistent approach to data access, with common
  exception hierarchy
• Simplifies working with JDBC, Hibernate, JDO etc
• Flexible MVC framework
• IoC/AOP integration
• Integration with a wide variety of popular
  products
• Gestalt
• More than the sum of its parts
• Hard to explain in a snappy phrase, but our users
  love it
• Solid, robust, works now
• In production in mission-critical apps now

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Spring focus

• Spring complements application servers like
  WebSphere
• Spring comes out of the application space, rather
  than the server space
• Spring avoids the need for costly in-house
  frameworks
• Can produce real savings
• Focus your developers on your domain
• Well-understood, generic, high-quality solution
• Facilitates testability, increase productivity
• Provides a simpler, yet powerful, alternative to
  the EJB component model in many applications
• But also plays well with EJB if you prefer to
  stick with EJB

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A layered framework

• Web MVC
• AOP framework
• Integrates with IoC
• IoC container
• Dependency Injection
• Transaction management
• Data access
• One stop shop but can also use as modules

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Web MVC

• Most similar in design to Struts
• Single shared Controller instance handles a
  particular request type
• Controllers, interceptors run in the IoC
  container
• Important distinguishing feature
• Spring eats its own dog food

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Web MVC Advantages over Struts

• Allows multiple DispatcherServlets
• More elegant than even Struts 1.1 solution
• DispatcherServlets can share an application
  context
• More flexible
• Interface not class-based
• Easier to customize
• Less tied to JSP
• Velocity, Excel, PDF etc
• Easy to implement custom Views

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Web MVC Advantages over Struts

• Cleaner MVC separation
• Cleanly separates controller, model and view
• Model is not tied to Servlet API or Spring API
• No need for custom ActionForms can reuse domain
  objects or TOs
• Much easier to unit test web tier, because Spring
  uses interfaces, not classes
• Integrates with middle tier with zero custom
  coding
• No more Service Locators or ad hoc Singletons

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Web tier integration

• But I love WebWork/Tapestry/Struts/JSF/whatever
• The customer is always right
• We dont dictate how to use Spring
• You can preserve your investment (tools etc)
• You can refactor to use what parts of Spring you
  need
• WebWork, Tapestry, Struts integration is seamless
• Support for JSF and Portlet development in Spring
  1.1 (August)
• JSF leaders (Ed Burns, David Geary) are working
  with us on Spring/JSF integration

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Spring in the Middle Tier

• Complete solution for managing business objects
• Write your business objects as POJOs
• Spring handles wiring and lookup
• Simple, consistent, XML format (commonest choice)
• But the IoC container is not tied to XML
• Application code has few dependencies on the
  containeroften no dependencies on the container
• Spring Pet Store has no dependencies on Spring
  IoC
• No magic annotations for IoC nothing
  Spring-specific
• Easy unit testing. TDD works!

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Spring in the Middle Tier

• The most complete IoC container
• Setter Dependency Injection
• Configuration via JavaBean properties
• Constructor Dependency Injection
• Configuration via constructor arguments
• Pioneered by PicoContainer
• Dependency Lookup
• Avalon/EJB-style callbacks
• I favour Setter Injection, but the Spring
  philosophy is that you make the choice
• We are not ideological.
• A good IoC container must provide sophisticated
  support for both injection models to allow use of
  legacy code

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Middle Tier Setter Injection

• public class ServiceImpl implements Service
• private int timeout
• private AccountDao accountDao
• public void setTimeout(int timeout)
• this.timeout timeout
• public void setAccountDao(AccountDao
  accountDao)
• this.accountDao accountDao
• // Business methods from Service
• rviceImpl"
• 30rty
• local"accountDao"/

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Middle Tier Constructor Injection

• public class ServiceImpl implements Service
• private int timeout
• private AccountDao accountDao
• public ServiceImpl (int timeout, AccountDao
  accountDao)
• this.timeout timeout
• this.accountDao accountDao
• // Business methods from Service
• rviceImpl"
• 30rg
• ructor-arg

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Middle Tier Dependency Injection

• Simple or object properties
• Configuration (timeout)
• Dependencies on collaborators (accountDao)
• Configuration properties are also important
• Can run many existing classes unchanged
• Autowiring
• Trivial to test application classes outside the
  container, without Spring
• Can reuse application classes outside the
  container
• Hot swapping, instance pooling (with AOP)

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Spring in the Middle Tier

• Advanced IoC features
• Can manage lists, maps or sets, with arbitrary
  nesting
• Leverages standard JavaBeans PropertyEditor
  machinery
• Register custom property editors
• Post processors

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Why AOP?

• AOP complements IoC to deliver a non-invasive
  framework
• Externalizes crosscutting concerns from
  application code
• Concerns that cut across the structure of an
  object model
• AOP offers a different way of thinking about
  program structure to an object hierarchy
• EJB interception is conceptually similar, but not
  extensible and imposes too many constraints on
  components
• Spring provides important out-of-the box aspects
• Declarative transaction management for any POJO
• Pooling
• Resource acquisition/release

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AOP IoC A unique synergy

• AOP IoC is a match made in heaven
• Any object obtained from a Spring IoC container
  can be transparently advised based on
  configuration
• Advisors, pointcuts and advices can themselves be
  managed by the IoC container
• Spring is an integrated, consistent solution

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Custom AOP

• Complements, rather then conflicts with, OOP
• Email administrator if a particular exception is
  thrown
• Apply custom declarative security checks
• Performance monitoring
• Auditing
• Caching

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AspectJ integration

• Coming in Spring 1.1 (August)
• Particularly relevant to WebSphere users given
  IBMs backing for AspectJ
• Integrates AspectJ aspects into Spring IoC
• Configure and parameterize aspects in a
  consistent way
• Will allow the use of the AspectJ pointcut
  expression language to target Spring advice
• Can mix Spring and AspectJ aspects within a
  consistent architectural model

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Spring DAO

• Integrated with Spring transaction management
• Unique synergy
• Gestalt again
• Doesnt reinvent the wheel.
• There are good solutions for O/R mapping, we make
  them easier to use
• Out-of-the-box support for
• JDBC
• Hibernate
• JDO
• iBATIS
• Model allows support for other technologies
  (TopLink etc)
• Consistent DataAccessException hierarchy allows
  truly technology-agnostic DAOs

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Spring DAO Consistent exception hierarchy
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Spring DAO JDBC

• Class library offers simpler programming model
  than raw JDBC
• Two flavours of usage
• Callbacks (JdbcTemplate)
• JDBC objects Model queries, updates and stored
  procedures as objects
• No more try/catch/finally blocks
• No more leaked connections
• Spring will always close a connection no scope
  for programmer error
• Meaningful exception hierarchy
• No more vendor code lookups
• Spring autodetects database and knows what
  Oracle, DB2 error codes mean
• More portable code
• More readable code
• catch (BadSqlGrammarException ex)
• Stored procedure support
• Can refactor to clean up JDBC without adopting
  Spring overall
• Incremental adoption Step by step

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Spring DAO Hibernate

• Manages Hibernate sessions
• No more custom ThreadLocal sessions
• Sessions are managed within Spring transaction
  management
• Works with JTA if desired
• Works within EJB container with CMT if desired
• HibernateTemplate makes common operations easy
• Simpler, consistent exception handling
• Many operations become one-liners
• Less, simpler, code compared to using Hibernate
  alone
• Portability Switch between Hibernate, JDO and
  other transparent persistence technologies
  without changing DAO interfaces
• Can even switch to JDBC where transparent update
  is not implied
• Mixed use of Hibernate and JDBC within the same
  transaction

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HibernateTemplate DAO example

• public class MyHibernateDao implements MyDao
• private HibernateTemplate hibernateTemplate
• public MyHibernateDao (net.sf.hibernate.SessionFa
  ctory sessionFactory)
• hibernateTemplate new HibernateTemplate(sessio
  nFactory)
• public Collection getWorkflows()
• return hibernateTemplate.find("from Workflow")
• rk.orm.hibernate.LocalSessionFactoryBean"
• local"dataSource"/
• mycompany/mappings.hbm.xml

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Spring DAO JDO

• Comparable to Hibernate support
• Mixed use of JDO and JDBC within the same
  transaction
• Will support JDO 2.0 features (detach) and vendor
  extensions in a portable manner
• All major vendors support similar concepts

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Spring Transaction

• Consistent abstraction
• PlatformTransactionManager
• Does not reinvent transaction manager
• Choose between JTA, JDBC, Hibernate, JDO etc with
  simple changes to configuration not Java code
• No more rewriting application to scale up from
  JDBC or Hibernate local transactions to JTA
  global transactions
• Use the simplest transaction infrastructure that
  can possibly work
• Programmatic transaction management
• Simpler API than JTA
• Use the same API for JTA, JDBC, Hibernate etc.
• Write once have transaction management
  everywhereTM

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Declarative Transaction Management

• Most popular transaction management option
• Built on same abstraction as programmatic
  transaction management
• Declarative transaction management for any POJO,
  without EJB even without JTA (single database)
• More flexible than EJB CMT
• Declarative rollback rules roll back on
  MyCheckedException
• Non-invasive Minimizes dependence on the
  container
• No more passing around EJBContext

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Make ServiceImpl POJO transactional

• public class ServiceImpl implements Service
• private int timeout
• private AccountDao accountDao
• public void setTimeout(int timeout)
• this.timeout timeout
• public void setAccountDao(AccountDao accountDao)
  
• this.accountDao accountDao
• public void doSomething() throws
  ServiceWithdrawnException
• ice.ServiceImpl"
• 30perty
• local"accountDao"/

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Make ServiceImpl transactional

• saction.interceptor.TransactionProxyFactoryBean"/
  
• PROPAGATION_REQUIRED,-ServiceWithdrawnExcep
  tion

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Make ServiceImpl transactional

• Rollback rule means that we dont need to call
  setRollbackOnly()
• Of course Spring also supports programmatic
  rollback
• Can run this from a JUnit test case
• Doesnt depend on a heavyweight container
• Can work with JTA, JDBC, Hibernate, JDO, iBATIS
  transactions
• Just change definition of transaction manager

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Make ServiceImpl transactional

• Alternative approaches, simpler in large
  applications
• Use auto proxy creator to apply similar
  transaction attributes to multiple beans
• Use metadata or another pointcut approach to
  apply transactional behaviour to multiple classes

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Spring J2EE

• No more JNDI lookups
• JndiObjectFactoryBean
• Generic proxy for DataSources etc.
• No more EJB API dependencies, even in code
  calling EJBs
• EJB proxies
• No more home.create()
• No more Service Locators or Business Delegates
• Codeless EJB access
• Callers depend on Business Methods interface, not
  EJB API
• Exposed via Dependency Injection (naturally)
• Maximize code reuse by minimizing J2EE API
  dependencies
• Spring does not prevent you using the full power
  of J2EE
• Full power of WebSphere lies under the covers
• Spring makes it easier to use effectively

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Spring OOP

• No more Singletons
• An antipattern as commonly used
• Program to interfaces, not classes
• Facilitates use of the Strategy pattern
• Makes good OO practice much easier to achieve
• IoC Dependency Injection keeps the container from
  messing up your object model
• Base object granularity on OO concerns, not
  Spring concerns
• Combine with transparent persistence to achieve a
  true domain model

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Spring Productivity

• Less code to develop in house
• Focus on your domain
• Reduced testing effort
• Try it and you wont look back
• Old J2EE has a poor productivity record
• Need to simplify the programming model, not rely
  on tools to hide the complexity

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Old J2EE vs Spring

• Write a SLSB
• Home interface
• Component interface
• Business methods interface
• Bean implementation class
• Complex XML configuration
• POJO delegate behind it if you want to test
  outside the container
• Much of this is working around EJB
• If you want parameterization it gets even more
  complex
• Need custom code, IoC container or environment
  variables (ouch)

• Implement a Spring object
• Business interface
• Implementation class
• Straightforward XML configuration
• The first two steps are necessary in Java anyway
• Oops, I really meant implement a Java object,
  not implement a Spring object
• If you want to manage simple properties or object
  dependencies, its easy

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Old J2EE vs Spring

• Use your SLSB
• Write a Service Locator and/or Business Delegate
  need JNDI code
• Each class that uses the service needs to depend
  on EJB interface (home.create) or you need a
  Business Delegate with substantial code
  duplication
• Hard to test outside a container

• Use your Spring object
• Just write the class that uses it in plain old
  Java
• Express a dependency of the business interface
  type using Java (setter or constructor)
• Simple, intuitive XML configuration
• No lookup code
• Easily test with mock object

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Productivity dividend

• Spring removes unnecessary code
• You end with no Java plumbing code and relatively
  simple XML
• If your Spring XML is complex, youre probably
  doing things you couldnt do the old way without
  extensive custom coding
• The old way you have lots of Java plumbing code
  and lots of XML
• A lot of the XML is not standard
• Combine with Hibernate or JDO for transparent
  persistence and the advantage is huge

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Quotes Plenty of choice from Spring users

• I use the Spring Framework daily and I've simply
  been blown away by how much easier it makes
  development of new software components
• Spring lets me port my business logic across
  those environments application server, Swing
  client with ease. That's why I love Spring.

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Quotes Plenty of choice from Spring users

• Lightweight containers make a lot of sense.
  Springs ability to decouple layers within an
  applications is very addictive.
• You will wonder how you ever developed anything
  in Hibernate without spring, it just makes it so
  much easier. You gotta love HibernateTemplate.
  You gotta love the session management.
• The proof of concept went up to 150 requests per
  second! Man, you guys did a hell of job with the
  whole thing. Spring MVC overhead is minimal and
  it took only 15 hours to implement it, thanks for
  the dependency injection!

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Quotes

• I'm a new user of spring and I have to say, it's
  great.  It's really speeding up our development
  time
• One of the great things for me about the Spring
  Framework is that it makes using some of those
  "old" technologies easier to bear
  theorg.springframework.ejb.support package is
  nice to use to reduce the amount of duplicate
  code around EJBs
• Spring now has the momentum to dominate the J2EE
  framework space OO guru and consultant Craig
  Larman

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The Spring community

• www.springframework.org
• 15 developers
• Around 6 core developers
• Significant number of contributors
• Architects and key developers
• Rod Johnson
• Juergen Hoeller
• Test-first development on the framework
• Vibrant community
• Very active mailing lists and forums
• JIRA Issue tracker at Atlassian
• Over 50,000 downloads total

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The Spring community

• At least six books coming out in 2004
• Spring Live (June) Matt Raible
• J2EE Without EJB (May) Johnson/Hoeller
• Professional Spring Development (Q4)
  Johnson/Risberg/Hoeller/Arendsen
• Better, Faster Lighter Java (Bruce Tate)
• Bruce is also writing an introductory Spring book
  for OReilly (due out Q4)
• Manning Spring in Action (Q4)
• Related projects
• Acegi Security for Spring

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Spring services Interface21

• Training
• Commercial support
• Consulting
• We offer more choices for companies who wish to
  form a strategic partnership with us
• We provide unique Spring and J2EE expertise

46
Whos using Spring (partial list)

• Banking
• Global investment bank
• 2 projects live with Spring MVC, IoC, AOP, JDBC
  10,000 users daily (whole Intranet)
• Even bigger project rolling out this month
  (WebSphere)
• German domestic bank
• Leading US bank online banking service (8m hits
  per day)
• At least three more global banks to my knowledge
• Several household names in US
• Defence
• Publishing
• Health care (WebSphere)
• Power generation (WebSphere)

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Whos using Spring (partial list)

• Government/NGO
• European Commission
• WHO
• CERN
• Several universities in the US and UK, including
• Rutgers University (New Jersey)
• Warwick University (UK)
• uPortal project (US University portal)
• Many sophisticated websites
• Used by several consultancies on multiple client
  sites
• Major European delivery tracking service
• Nominet
• FA Premier League football

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Where it all began

• Describes the motivation for Spring and basic
  concepts
• Practical approach to J2EE development that works
• One of the first expressions of lightweight J2EE

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Episode 2

• Describes the Lightweight Container Architecture
  in detail
• Practical guide to more efficient, more
  productive J2EE
• Not just a polemic
• Not purely about Spring, but
• Uses Spring for all examples
• Discusses all key parts of Spring

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Questions