Spring survey
- 1. An Survey of Spring Chris Roeder March, 2011 This talk summarizes a lot of what is available in: Spring In Action , Craig Walls, Manning 2008
- 2. Spring is a collection of frameworks: IoC – an “Inversion of Control” AKA: Dependency Injection Framework Data Access,Transaction Management, Security
- 5. Aspects – a way to deal with “cross cutting concerns”
- 6. MVC – an alternative to web application frameworks like Struts
- 7. Spring does not re-invent the wheel Uses existing logging frameworks
- 8. Uses existing anything: ORM, transactions, Aspects, Remoting, etc.
- 9. Spring is there to provide “portability” between frameworks that share a purpose and interface
- 10. Spring Frameworks are Abstractions Frameworks are collections of Java interfaces
- 11. Implemented by a variety of solutions: Hibernate, JPA, Toplink “Injected” into your code by the config file using the Java Bean Interface (more)
- 12. Leaving your code simple and full of POJOs (more later)
- 13. When needs require a different implementation, very easy to change the config file with no code changes
- 14. Detail: Java Bean “A JavaBean is a Java Object that is serializable, has a nullary constructor, and allows access to properties using getter and setter methods.” http://en.wikipedia.org/wiki/JavaBean Not an Entity Java Bean or EJB
- 15. Detail: POJO “The name is used to emphasize that a given object is an ordinary Java Object, not a special object, and in particular not an Enterprise JavaBean” http://en.wikipedia.org/wiki/Plain_Old_Java_Object Meaning it's not tied to a particular framework.
- 16. Inversion of Control or Dependency Injection? Inversion of Control is a general concept that relates to event-driven programming where the stream of events dictates execution.
- 17. Dependency Injection is a more specific concept that refers to setting values on objects (Java Beans) from an external source.
- 18. Spring calls the framework IoC.
- 19. I call the concept used here DI.
- 20. Detail: IoC Dependency Injection (DI) involves abstracting out the introduction of a project's components.
- 21. Even with good modularity, you still hard-code them together with code like this:
- 22. public static void main(String args[]) { DataProvider dp = new DataProvider(); CorpMetrics metrics = new CorpMetrics(); metrics.calculate(dp);
- 23. Detail: IoC 2 In other situations, JDBC in EJB for example, collaborators aren't hard-coded, but find each other at runtime:
- 24. A JDBC setup finds its database connection by consulting JNDI, making environmental assumptions: Context initContext = new InitialContext(); Context envContext = (Context)initContext.lookup("java:/comp/env"); DataSource ds = (DataSource)envContext.lookup("jdbc/myoracle"); Connection conn = ds.getConnection(); ( http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-howto.html )
- 25. Changes still involve changing the java code.
- 26. Detail: IoC 3 Separate classes allows flexibility
- 27. Hard-coded constructor calls limit it.
- 28. Unit Testing with different configurations is made easier.
- 29. IoC is used as a supporting technology throughout Spring
- 30. UIMA users, as described in a 2009 poster paper, would find this eerily familiar A bit of programmer humor would involve using uimaFIT and Spring to define a pipeline in a Spring config file instead of a CPE.
- 31. Detail: IoC 4 Alternate implementations require interfaces:
- 33. Create “new” implementations of Classes that implement them.
- 34. Easy to swap with a different implementation when both implement the same Java interface.
- 35. Also works to enable a kind of multiple inheritance in Java.
- 36. Survey: Data Access POJO model entities can be stored in any ORM tool, just plain JDBC or others
- 37. Operations on entities built in Data Access Objects (DAO) GetById(), GetListWhere(), Update(), etc. Spring provides “templates” to make building DAOs easy
- 38. BTW, these are used in FLEX integration
- 39. Survey: Transaction Management Abstracts on top of JDBC, Hibernate, JPA, JMS, EJB transaction.jta.* classes
- 40. Databases handle their own transactions: START TRANSACTION, SAVE TRANSACTION EJB containers allow transactions between multiple systems
- 41. Coding to Spring allows flexibility and growth
- 42. Survey: Remote Access Compares to RMI, SOAP WS, Hessian, Burlap
- 43. Abstracts the concept of remoting and provides different implementations.
- 44. Client and service objects are POJOs.
- 45. Can make use of JSR-181 Web Services Metadata annotations
- 46. Survey: Dynamic Modules Spring-DM is an implementation and integration of OSGI modules into Spring.
- 47. provide another layer of encapsulation over the concept of Class. Now you can have private and public classes as members of a module (jar).
- 48. allow for a lifecycle, so module can have a “running” state.
- 49. provide better naming, so versions can be included.
- 50. provide restricted “class space”, allowing for more than one version of a class at the same time.
- 51. More: Yuriy is working on this
- 52. Survey: Aspects Cross-Cutting Concern: “functions that span multiple points of an application”
- 54. Makes use of a proxy facility in Java reflection. Instead of creating and using a new object, you create the object and a proxy around it. Then use the proxy in it's place.
- 55. The proxy intercepts function calls and allows implementations of a Handler interface to intercept them. Other Implementations exist, but are intrusive.
- 56. Survey: MVC Spring has a Model, View, Control (MVC) framework for web applications. It separates code into three types: Model – the data and functions to manipulate it
- 57. View – the JSP pages to render a web page
- 58. Controller – the plumbing or routing A kind of “Model 2” architecture where a controller servlet controls creates beans and introduces them to JSPs Model 1 architecture is js JSP and Bean, leaving much to the JSP and scriptlets.