Composable Software Architecture with Spring

Composable Software Architecture
with Spring
Sam Brannen
@sam_brannen
Java Breeze | Odessa, Ukraine | 18 May 2013

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Sam Brannen
•  Spring and Java Consultant @ Swiftmind (Zurich)
•  Developing Java for over 15 years
•  Spring Framework Core Committer since 2007
•  Spring Trainer
•  Presenter on Spring, Java, OSGi, and testing

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Swiftmind
Your experts for Enterprise Java
Areas of expertise
•  Spring Framework
•  Java EE
•  OSGi
•  Agile Methodologies
•  Software Engineering Best Practices
Headquarters
•  Zurich, Switzerland
•  @swiftmind
•  http://www.swiftmind.com

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Agenda
•  Enterprise Applications
•  What we’ve learned as a community
•  Composable Software Architecture
•  Java EE + Open Source
•  How Spring fits into the picture
•  Spring 4.0 Roadmap

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Modern Enterprise Applications

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What does "enterprise" mean?
Enterprise software is software used in organizations, such
as in a business or government, as opposed to software
used by individuals. Enterprise software is an integral part of
a (computer based) Information System.
-Wikipedia

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OK, sure... but what does that mean to developers?

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Furthermore …
Enterprise software typically has interfaces to other
enterprise software and is centrally managed.
- Wikipedia

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Ahh, now we’re getting somewhere!

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Typical Enterprise Application
•  Supports enterprise business process
•  Is relatively large
•  Should be robust, scalable, and offer high performance
•  Does not run in isolation
•  Interacts with multiple external systems and services …

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SOAP Web Services, REST Web Services

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Web and Mobile clients, etc.

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But each of these has its own APIs and potentially different
protocols and exchange formats!

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So how should we design such enterprise applications?

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What we’ve learned as a community

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Things to avoid
•  Tight coupling to the container or frameworks
•  Tight coupling to protocols and exchange formats in our
service layer
•  Monolithic deployment units
•  Anemic domain models
•  Bloated transaction scripts
•  Code tangling and scattering

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What we should aim for
•  Modularity
•  Layered architecture with
–  a canonical domain model
–  a dedicated orchestration layer
•  Separation of concerns
•  Externalized environment-specific configuration
•  Design for testability

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How we achieve it
•  OOA / OOD / OOP
•  (@)POJO Programming Model
•  Marshaling and automatic type conversion
•  Dependency Injection (DI)
•  Inversion of Control (IoC)
•  AOP / Interceptor Model
•  Automated out-of-container testing and CI

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Composable Software Architecture

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Composability
Composability is a system design principle that deals with
the inter-relationships of components. A highly
composable system provides recombinant components that
can be selected and assembled in various combinations
to satisfy specific user requirements. (Wikipedia)
•  Self-contained (modular)
•  Typically stateless

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But it's not just about modularity and statelessness.

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It's a different way of thinking,

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a different way of designing,

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a different kind of architecture,

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Think about different ways the same components can be...

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to meet different business requirements

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or to interact with different systems.

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Composable Architecture Visualized
Infrastructure
Repository
Service
Orchestration
DomainModel

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How is this new?
•  To be honest, it’s not really new,
–  if you just look at the diagram…
•  The web tier or presentation layer has always effectively
been a type of orchestration layer.
•  The difference is that we re-use all of the other layers
with multiple types of orchestration simultaneously!

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Orchestration Layer
•  Lies at the heart of a composable architecture
•  Orchestrates all interactions with the service layer
–  potentially interacting directly with repositories (e.g.,
in batch processing)
•  Handles external protocols
•  Converts from external formats into our canonical domain
model
•  Thereby… allowing application services to be composed in
a multitude of different ways!

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Common Types of Orchestration
•  Web controller
–  HTTP, HTTPS :: HTTP request and response
•  REST or SOAP Web Service endpoint
–  HTTP/HTTPS :: XML, JSON, binary, …
•  JMS or AMQP listener (or message listener container)
–  JMS Message types, domain entities, …
•  Messaging endpoint (e.g., gateway + service activator)
–  Web service, FTP, file system, email, …
•  Batch component (e.g., reader, writer, processor)
–  Files, SQL, …

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What's good about Java EE?
•  Set of common enterprise standards for Java
•  Consistent across containers and vendors (mostly)
•  Great tooling and build support
•  Catching up with innovation in open source
–  Hibernate à JPA
–  Spring DI / Guice / Seam à CDI

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if everything you need is in that shop.

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But if Java EE doesn’t offer what you need…

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either in a Java EE container

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or in an alternative light-weight container.

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Open Source Frameworks fill the Gaps
•  Web frameworks and UI components
•  NoSQL
•  Big Data
•  AMQP
•  Mobile
•  Social Media
•  Batch
•  Enterprise Integration (EAI)
•  …

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How Spring fits into the picture

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Core Spring (Framework)
•  DI + IoC + AOP
•  Declarative
–  transactions, caching, validation, formatting
•  Spring MVC and REST
•  JMS Message Listener Container
–  Message-driven POJOs
•  Testing framework

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Dependency Injection and Inversion of Control collectively
decouple application code from the deployment environment

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DI + IoC à POJO Programming Model

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POJO Programming Model + AOP à Composability

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Spring is an Ecosystem
•  Spring MVC
•  Spring REST
•  Spring Web Flow
•  Spring Security
•  Spring Web Services
•  Spring Batch
•  Spring Integration
•  Spring Data
•  Spring Mobile
•  Spring Social
•  Spring AMQP
•  …

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Spring MVC and REST
•  @Controller annotated components serve as MVC
handler methods and REST endpoints
•  Automatic type conversion
•  Data binding to domain entities
•  Marshaling
–  JSON, JAXB, Castor, XMLBeans, JiBX, XStream, …
•  Handler methods and endpoints orchestrate the service
layer

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Spring Web Services
•  @Endpoint annotated components serve as SOAP Web
Service endpoints
•  Marshaling (OXM)
–  JAXB, Castor, XMLBeans, JiBX, XStream
•  Endpoint methods orchestrate the service layer

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Spring JMS
•  Message listener containers (MLC) support
–  JMS MessageListener API
–  Message-driven POJOs
•  Automatic type conversion from JMS Message types into
–  String, Map, Object, byte[]
–  Customer converters also supported
•  Marshaling
–  Spring OXM, customer solutions, etc.
•  MLC orchestrates the service layer

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Spring Integration
•  Inbound and outbound messaging gateways
–  Handle external protocols and APIs
–  Too many to mention here!
•  Automatic type conversion for method arguments and
return types in Service Activators
•  Marshaling and custom type conversion also supported
•  The service layer can be orchestrated via declarative
configuration (e.g., service activators in XML)

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Composable Architecture – with Spring
Infrastructure
Repository
Service
DomainModel
Spring REST
Spring MVC
Spring JMS
Spring Integration
Spring Batch
Spring WS

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Composable Architecture Checklist
þ  Modularity
þ  Layered architecture
þ Canonical Domain Model
þ Orchestration: web, batch, integration, web services
þ Service
þ Repository
þ Infrastructure
þ  POJO programming model
þ  Separation of concerns
þ  Externalized environment-specific configuration
þ  Testability, automated testing, and CI

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1st Class Support for Java 8 based apps
•  Language features such as lambda expressions
–  for callbacks with templates
–  for concurrent execution
•  think fork/join, map/reduce, etc.
•  APIs such as JSR-310 Date and Time
–  Alongside Spring’s existing support for JodaTime

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Configuring Spring with Groovy 2
•  Configuring and implementing Spring-style applications
using Groovy 2.x
•  Groovy-based bean definitions
•  Groovy as the language of choice for an entire
application, as a direct and straightforward alternative to
Java source files
•  Groovy 2.0's static compilation support completes the
picture here

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Support for Key Java EE 7 Technologies
•  JMS 2.0
•  JPA 2.1
•  Bean Validation 1.1
•  Servlet 3.1
•  And fully covering JCache 1.0

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Enabling WebSocket-style Architectures
•  Support for JSR-356 compliant runtimes
•  Also supporting related technologies

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Fine-grained Eventing and Messaging
•  Introducing fine-grained eventing and messaging within
the application
•  Building on our existing application event mechanism
•  Aligned with our JMS message listener mechanism

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Pruning and Dependency Upgrades
•  Removing a variety of deprecated packages across the
framework
–  See Spring Framework 3.2's deprecations!
•  Raising minimum dependencies to Java 6+
–  Java SE 6+ and Java EE 6+
–  with some compromises for EE 5++ servers

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Further Resources
•  Spring Projects
–  http://www.springsource.org/projects
–  Reference Manuals
–  Javadoc
•  Spring Forums
–  http://forum.springframework.org
•  Spring JIRA
–  http://jira.springframework.org
•  GitHub Repositories
–  https://github.com/SpringSource

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Blogs
•  Swiftmind Team Blog
–  http://www.swiftmind.com/blog/
•  SpringSource Team Blog
–  http://blog.springsource.com/

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Q & A
Sam Brannen
twitter: @sam_brannen
www.slideshare.net/sbrannen
www.swiftmind.com

Composable Software Architecture with Spring

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