Building Enterprise Web Applications with Spring 3.0 and Spring 3.0 MVC

1. Building Enterprise Web Applications with Spring 3.0 and Spring 3.0 MVC JavaOne 2010 By AbdelmonaimRemani abdelmonaim.remani@gmail.com

2. License • Creative Commons Attribution-NonCommercial 3.0 Unported • http://creativecommons.org/licenses/by-nc/3.0/

3. Who Am I? • Software Engineer at Overstock.com • Particularly interested in technology evangelism and enterprise software development and architecture • President and Founder of a number of organizations • The Chico Java User Group • The Chico Flex User Group, • The Chico Google Technology User Group. • LinkedIn • http://www.linkedin.com/in/polymathiccoder • Twitter • http://twitter.com/polymathiccoder

4. Warning This presentation is very long and covers a lot of material

5. Introduction

6. Enterprise Application Software (EAS) • Complex • In terms of requirements • Functional • Non-Functional • Execution • Performance • Reliability • Security • Evolution • Testability • Maintainability • Extendibility • Scalability (Horizontal and Vertical)

7. Enterprise Application Software (EAS) • In the words of Edsger W. Dijkstra: • […] The Separation of Concerns […] is yet the only available technique for effective ordering of one’s thoughts […] • Artificially Reducing complexity by means of Abstraction • Specific Choices of abstraction • Produces a architectures

8. Modern Enterprise Application • The Architecture • Layered / N-Tiered • Presentation Layer • Web Layer • Service Layer • Persistence Layer • Aspects • Middleware • Other

9. Frameworks • A Framework is an architecture • A well-defined structure to solve a problem • A pre-existing hierarchy to be extended • Library • Framework vs. Library • Invoking vs. being invoked • Generic vs. specific • Tools • Compiler, debugger, etc… • Scaffolding and other utilities • Etc…

10. Frameworks • Heavyweight vs. Lightweight • The need for a platform or a stack (JEE as example) • The ability to load in-demand necessary components • The memory footprint • The build size • Deployment ease • Etc…

11. The Spring Framework

12. What is Spring? • Application Framework • Java • Other implementations are available (Spring .NET) • Open-Source • Lightweight • Non-Invasive (POJO Based) • Extendible • A platform with well-defined extension points for other frameworks • By Rod Johnson • Expert One-on-One J2EE Design and Development, 2002 • J2EE without EJB, 2004 • Became the De facto standard of Java Enterprise Applications

13. Spring Source: Spring 3.0.x Framework Reference http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/htmlsingle/spring-framework-reference.html 20 Modules

14. Libraries • Wrappers for most popular frameworks • Allowing injection of dependencies into standard implementation • Struts • JSF • Apache Tapestry • Etc… • Full Integration with the JEE stack

15. The Address Book

16. The Address Book • The Address Book from polymathic-coder.com • A web application for Contact management

17. Functional RequirementsUse Case 1 - Contact Management • Details: • As a user I should be able to view, add, delete, and edit personal contacts data on my address book including: • First Name • Last Name • Email • Phone Number • Image • Primary Actors: Regular user / Administrator • Assumptions: • The user is authenticated and has proper privileges to access the Contact Management Area • Access is granted both through the web interface and a RESTful API

18. Functional RequirementsUse Case 1 - Contact Management • Business Rules • A First Names are required • Phone Numbers must be valid US phone numbers • Emails must be valid

19. Functional RequirementsUse Case 2 - User Management • Details: • As an administrator I should be able to view, add, delete, and edit the user data including: • Username • Password • Role (Regular or Administrator) • Whether the account is enabled or not • Email • Primary Actors: Administrator • Assumptions: • The user is authenticated and has proper privileges to access the User Administration Area • Access is granted through the web interface

20. Functional RequirementsUse Case 2 - User Management • Business Rules • Username is required and must be unique • Passwords must be complex (The should contains at least 1 lowercase letter, 1 uppercase letter, 1 digit, and 1 special character) • Emails must be valid • An email must be sent to the newly created user

21. Functional RequirementsUse Case 3 - Reporting • Details: • As an administrator I should be able to view audit and health check reports • Primary Actors: Administrator • Assumptions: • The user is authenticated and has proper privileges to access the Reporting Area • Access is granted through the web interface • The reports are periodically generated by the system

22. Non-Functional Requirements Security • RBAC (Role-based access control) • Authentication • Form-based • Http Basic • Authorization • Security Roles • Regular User • Access to personal contact management area • Administrators • Access to personal contact management area • Access to user administration area • Access to reporting area • Access Control • No Rules • Transport Security • Not required

23. Spring Core

24. Inversion of Control • The problem: • Acquiring Resources via • Instantiation of a concrete class • Using a static method of a singleton factory • Using a Directory Services API that allows for discovery and lookup (JNDI for example) • Etc.. • Creates hard dependencies • Coupled code is hard to reuse (DRYness) • Painful Unit Testing

25. Inversion of Control • The Solution: • Coding against Interfaces • Inversion of Control: Dependency Injection • Reflectively supply external dependency at runtime • The Hollywood principle: “Don’t call us, we’ll call you” • Wait a minute this a lot of work! • Spring to the rescue

26. Spring Core Source: Spring 3.0.x Framework Reference http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/htmlsingle/spring-framework-reference.html • Container  • POJO • Configuration Metadata • XML-Based • Annotation-Based • Java-based

27. JSR 330 – Dependency Injection for Java Spring Annotations @Autowire @Qualifier JSR 330 • @Inject • @Named • JSR 250 -  Common Annotations • javax.annotation • JSR 299 – Contexts and Dependency Injection • Scopes and contexts: javax.context • Dependency injection service: javax.inject • Framework integration SPI: javax.inject.manager • Event notification service: javax.event

28. Stereotypical Spring • Used to mark a class that fulfills a role or a stereotype • Stereotyped classes can be automatically detected • Spring Stereotypes • @Component • @Repository • @Service • @Controller

29. Domain Model

30. Domain Model

31. Domain Model • A modelof the “concepts” involved in the system and their relationships • Anemic Domain Model • POJOs (Plain Old Java Objects) or VOs (Value Objects) • Clear separation between logic and data • Parallel object hierarchies are evil • Metadata is interpreted depending on the context as the object moves across the layers of the application • Object-Relational mapping to persistent entities • Validation • Marshaling / Un-marshaling • Etc…

32. JSR 303 - Bean Validation Source: Hibernate Validator Reference Guide 4.1.0.Final http://docs.jboss.org/hibernate/stable/validator/reference/en-US/html_single/ Ensuring the correctness of data based on a set predefined rules

33. JSR 303 - Bean Validation Source: Hibernate Validator Reference Guide 4.1.0.Final http://docs.jboss.org/hibernate/stable/validator/reference/en-US/html_single/ javax.validation Reference Implementation: Hibernate Validator

34. Domain Model • Instantiation (Items 1 & 2 of Josh Bloch’s Effective Java) • Static Factories • Telescoping • Provide builders • Override the default implementations of hashCode(), toString(), and equals(Object) methods • Use Pojomatic at http://pojomatic.sourceforge.net/ • Be aware of any circular dependency in your model • Versioning • @Version of JSR 317 – JPA 2.0

35. Persistence Layer

36. Persistence Layer • A logical encapsulation of classes and interfaces whose responsibilities fall within the scope of: • Create, Read, Update, and Delete (CRUD) operations on persistence storage mechanisms such as file systems and Database Management Systems (DBMS) • Interacting with Message-Oriented Middleware (MOM) infrastructures or Message Transfer Agents (MTA) such as JMS or mail servers

37. JSR 317 – JPA 2.0 • javax.persistence • Reference Implementation EclipseLink • Primer • A persistence entity is a POJO whose state is persisted to a table in a relational database according to predefined ORM metadata • An entity is managed by an Entity Manager • Do we still need a Persistence Layer? • Highlights • Support for JSR 303 validation

38. Spring Data Access / Integration • Beans Stereotyped with @Repository • Enables exception translation to a consistent exception hierarchy • Run-time exceptions and do not have to be declared or caught • Use JPA annotations to inject EntityManager and EntityManagerFactory • @PersistenceContext • @PersistenceUnit • Follow a convention (I suggest CRUD) • Declaring transaction semantics • @Transactional

39. Spring Data Access / Integration • Java Mail API • javax.mail • Spring Helpers for various Templating Engines • Velocity • FreeMarker

40. Persistence Layer • Testing • JUnit • Take advantage of what JUnit 4.7 has to offer (Explore Theories, Rules, Etc…) • Libraries • DbUnithttp://www.dbunit.org/ • Dumpster http://quintanasoft.com/dumbster/ • Consider HADES http://redmine.synyx.org/projects/show/hades

41. Service Layer

42. Service Layer • A logical encapsulation of classes and interfaces that provide the system functionality consolidating Units of work. Service layer classes should be: • Transactional • Stateless • Beans Stereotyped with @Service • Follow a convention (I suggest VADER)

43. Web Layer

44. Web Layer • A logical encapsulation of classes and interfaces whose responsibilities fall within the scope of: • Navigational logic • Rendering page views in the proper order • As simple as mapping a single URL to a single page • As complex as a full work flow engine • Web concerns (Request variables, session variables, HTTP methods, HTTP response codes, Etc…) should be separated from business logic

45. Web Layer • Two types of Web Frameworks • Request / Response Web Frameworks • Wrap the Servlet API • Adopt push model • Compile result • Push it out to be rendered in a view • Struts, Spring MVC, Etc… • Component Web Frameworks • Dot only hide the Servlet API • Event-driven component • JSF, Tapestry, Etc…

46. Spring MVC

47. Spring MVC • Request / Response Web Frameworks • A Front Controller Pattern • One Dispatcher servlet • Application Contexts • Application Context • Web Application Context

48. Spring MVC - Controllers • The promise Non-invasiveness • Fully annotation-driven • No extension of framework classes • No overriding methods • Controllers • Beans (Spring Managed-POJOs) Stereotyped with @Controller

49. Spring MVC - Controllers • Mapping Rules • @RequestMapping • By • Path • HTTP method • Query Parameters • Request Headers

50. Spring MVC - Controllers • Handler Methods • Parameters are request inputs • Request data • @RequestParam • @PathVariable • @RequestHeader • @CookieValue • Command Objects (Domain Objects) • Injection of standard objects • Automatic Type Conversion • Custom Type Conversion • JSR 303 Support • @Valid • Exposing reference data to the views • @ModelAttribute