Domain Driven Design Development Spring Portfolio

Domain Driven Design & Development with Spring Portfolio Srini Penchikala Ann Arbor Java User Group February 24, 2009

About the Speaker • Enterprise Architect • Writer: InfoQ, TSS, ONJava, DevX Java, java.net • Speaker • Detroit Java User Group Leader • Using Java/JEE since 2000 • SOA/Web Services since 2006 • PowerPoint since September 2008 2

Presentation Goal “What” Domain Driven Design (DDD) is and “How” Spring Portfolio helps in implementing a DDD project 3

Format Interactive  Demos  Duration: ~45 minutes  Q&A  4

Before we start… • How many have heard of Domain Driven Design before? • How many are currently using DDD? 5

Agenda • Domain Driven Design & Development • Spring Portfolio • Dependency Injection / AOP / Annotations • Spring Security (Demo) • Architecture Enforcement (Demo) • Code Generation (Demo) • Conclusions 6

Layered Architecture Diagram 8

Architecture Layers User Interface  Application  Domain  Infrastructure  9

Domain Layer Represents concepts of business,  information about business situation, and business rules. Maintains state reflecting the business  situation. This layer is the heart of business  software*. 10

J2EE Architecture Model HTTP Application Controller Session Management Transaction Management Facade Caching Data Access Data Access Object Persistence Domain Object * Notes: • No real Domain Layer • Business Logic in Façade Layer (Stateless Session Beans ) • Direct Access to Data Access Objects (CRUD logic is infrastructure not business ) • *Domain objects are really Persistence Data Store classes with getters /setters Database • Infrastructure concerns have overtaken/ overshadowed the domain concerns 11

The Problem Architects/Developers are thinking only about  infrastructure. Most of the development time is still spent on  writing plumbing code instead of real business logic. We have lost real OOP  12

Domain Driven Architecture 13

Domain Driven Design & Development 14

Domain Driven Design What: Domain Driven Design (DDD) is about  mapping business domain concepts into software artifacts. Why: To create better software by focusing on a  model of the domain rather than the technology. 15

Domain Driven Design Is not a:  new technology  new framework  JSR standard  Is a:  design pattern  16

Advantages Promotes high cohesion and low coupling  in the application code Easy to test domain components  Business (domain) logic is isolated from  non-domain and infrastructure code Adding/changing services does not  influence the domain or other services. 17

Development Styles Transaction Script  Table Module  Domain Model  18

Development Styles A single instance that handles the • business logic for all rows in a database table or view. Choose the right style for the right application/service Source: Patterns of Enterprise Application Architecture, Martin Fowler 19

DDD Manifesto (Business) Domain Infrastructure Domain State & Behavior Persistence   Business Logic Transaction Management   Business Rules Remoting   Scheduling  20

Domain Objects Domain objects are instances of real  entities which hold any knowledge or activity of the business domain. 21

Main Elements Entities  Objects defined by their identity, which remains  same throughout the life of software Value Objects  Immutable objects that have no identity & are used  to describe an attribute of another object. (Domain) Services  Objects that have no state & only have a defined  behavior that’s not part of any domain object. 22

Other Elements Module:  A method of organizing related concepts and tasks  in order to reduce complexity. Domain object Lifecycle is managed by:  Aggregate  Factory  Repository  23

DDD Thought Process Start with domain entities and domain logic  Basic domain-driven & object-oriented principles  Mentally start without a quot;servicequot; layer  See how far you can get  Add service level as required  You can refactor to DDD  Source: Domain Driven Design with AOP and DI, Presentation by Ramnivas Laddad 24

DDD Lifecycle Diagram 25

Spring Framework • Separation of concerns (business v. infrastructure) • POJO Based Design • Business domain first, infrastructure concerns second • Agile Development and Testing 27

Spring Philosophy 28

Spring Portfolio Spring Core  Spring AOP  Spring Security  Spring MVC/Spring WebFlow  29

The Project Project Management  Agile Methodology (SCRUM)  Iterative Design, Development, Unit Testing and  Refactoring. Architecture  Focus on business domain & alignment with  business model Isolation & Modularity  Loosely coupled with other layers  30 POJO programming model. 

Design Recipe Object Oriented Programming (OOP)  Dependency Injection (DI)  Aspect-oriented Programming (AOP)  Annotations  32

DDD with OOP Principles Domain Element State/Behavior Entity, Value Object, State and Behavior Aggregate Data Transfer Object State only Service, Repository Behavior only 33

Dependency Injection • Decouple and manage the dependencies of the components in the application • DI Frameworks: • Spring • Google Guice • Pico Container 34

DI Use Cases Service  Domain Classes  Transaction Manager  Domain  Data Access Object (DAO)  DAO class  Data Source  JPA Entity Manager  35

Domain Object DI • @Configurable annotation 36

Aspect-oriented Programming • Allows developers to add behavior to objects in a non-obtrusive manner through use of static and dynamic crosscutting. • Main goal is to code cross-cutting concerns in separate modules and apply them in a declarative way. 37

AOP Use Cases Framework Built-In Aspects  Transaction Management  Security  Custom Aspects  Profiling  Caching  Rules  38

Annotations • Added in Java SE 5.0 as Java Metadata facility (JSR 175). • Provide a way to add metadata to program elements. • Defined by nearly every recent JSR standard. • Also include a mechanism for adding custom annotations to the Java code*. 39

Annotations For Domain Elements Layer Domain Element Annotation Domain Entity, @Entity (JPA), Value Object @Configurable Domain Repository @Repository Domain Service @Service Application Controller @Controller All All @Component 40

Custom Annotations Use Cases • Caching • Validation 41

Custom Annotations • Implementation Options • Reflection • Annotation Processing Tool (APT) • Byte-code Instrumentation (Javassist) • Aspects/AOP (AspectJ and Spring AOP) 42

Domain Aspects Data Access  Persistence  Transaction Management  Domain Security  Business Operation Retry  Caching  44

Persistence & Txn Management JDBC  JPA w/ Hibernate, OpenJPA, EclipseLink  (TopLink) Spring JPA Utils & Data Source DI  Spring JTA Support  – Transactions are managed in Service classes using quot;@Transactionalquot; annotation 45

Spring Security Declarative Application Security support  Fits in very well with Spring Framework  Authentication  Authorization  URL level  Domain Object  Service Method  46

DEMO 47

Architecture Enforcement • Domain Driven Design Rules • Enforcement using Aspects and AOP 49

Rules – Compile Time Service classes should not depend on  Application layer classes DAO classes should only be called from  Domain classes 50

DEMO 51

Rules – Run Time Business operation retry  Caching  System Settings (using AOP)  Application Variables/Business Data (using  Annotations) 52

DEMO 53

Code Generation Write: XSD  Domain / Service  Code Generate: DAO interface and implementation  Facade (EJB's & WebServices)  DTO's  Unit Tests (including test data)  Spring configuration files  55

Code Generation Tools openArchitectureWare (oAW)  AndroMDA  Aceleo Spring Module  Skyway Builder  56

DEMO 57

Tools Spring for:  Scheduling (Quartz)  Configuration Management (Commons  Configuration, JMX) Hibernate Tools (for DDL generation)  Dozer (DO/DTO Assembly)  58

DDD Lifecycle Diagram Revisited 59

Conclusions • Domain First, Infrastructure Second • Layered Architecture & Separation of Concerns • Always keep the quot;contextquot; in mind • Balance between the quot;rightquot; vs. the quot;right nowquot; • Upcoming Java/JEE releases focus on development & deployment simplicity • Spring 3.0, Java EE 6, JPA 2.0, EJB 3.1 61

References • Domain Driven Design and Development In Practice (http://www.infoq.com/articles/ddd-in-practice) • Domain-Driven Design Website (http://www.domaindrivendesign.org/) • Domain-Driven Design by Eric Evans • Applying Domain-Driven Design and Patterns, Jimmy Nilsson • Patterns of Enterprise Application Architecture, Martin Fowler • Can DDD be Adequately Implemented Without DI and AOP (http://www.infoq.com/news/2008/02/ddd-di-aop) 62

Contact Information • Domain-Driven Design and Enterprise Architecture articles on InfoQ. • InfoQ website (http://www.infoq.com) • E-Mail: srinipenchikala@gmail.com • Blog: http://srinip2007.blogspot.com 63

Q&A 64

Thank You • Thank you for your attention • Feedback survey 65

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Domain Driven Design Development Spring Portfolio

by Srini Penchikala

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