1. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Optimizing J2EE Applications A Comparison of J2EE Design Idioms and their Performance Presented by Maciej Zawadzki mbz@urbancode.com

2. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Outline Introduction to EJBs EJB Performance Benchmark Beyond Performance: Code that is Simple and Easy to Maintain

3. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Introduction to EJBs –Three Tiered Architecture –Stateless Session EJBs –Stateful Session EJBs –Entity EJBs –Distributed Objects –Client View of EJBs EJB Performance Benchmark Beyond Performance: Code that is Simple and Easy to Maintain

4. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Three Tiered Architectures Middle Tier houses system level services such as: –Remote access between clients and data sources –Session and transaction management –Security management –Resource access management (dbs. connection pooling)

5. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. J2EE Three Tiered Architecture The EJB container and Web container make up the J2EE middle tier.

6. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Stateless Session EJBs Not tied to any client No data kept between method invocations Do not survive beyond the lifetime of the J2EE server Can access other resources available through the J2EE server

7. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Stateful Session EJBs Tied to a single client Can keep session data that survives between method invocations Do not survive beyond the lifetime of the J2EE server Can access other resources available through the J2EE server

8. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Entity EJBs Provide an object oriented representation of a row of data in a database Not tied to any client and can execute on behalf of multiple clients Built in protocol for data persistence via ejbLoad() and ejbStore() methods

9. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Distributed Objects Typical distributed object systems rely on Stub object on the client side to provide a proxy for the server side object. Method calls on the proxy are communicated to the server using a wire protocol. Arguments and return values are marshaled to and from the network data streams.

10. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Client View of EJBs Home interface provides remote access to a factory object Remote interface declares the business methods available on the EJB

11. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. EJB Performance Benchmark Introduction to EJBs EJB Performance Benchmark –Five Design Idioms –Four Tests (measuring relative performance of each idiom) –Benchmark Results –Explanation of Results –Strategy for Optimized Performance Beyond Performance: Code that is Simple and Easy to Maintain

12. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Benchmark Scenario Benchmark is a section of a J2EE application. Each inventory item consisted of: number, name, description, price, weight, weight unit of measure, manufacturer name. A database containing 1,000 records representing fictional inventory items was created.

13. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Five Design Idioms Fine Grained Entity Bean (FGE) – often used by beginners to Enterprise Java Beans Coarse Grained Entity Bean (CGE) – the best performing Entity Bean idiom typically used in practice Optimized Entity Bean (OE) – the best performing contender that still uses Entity Beans Session over Entity Bean (SE) – typically advanced as a “best practice” in trade media Coarse Grained Session Beans (CGS) – the proposed best performer

14. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Fine Grained Entity Bean Design Idiom The client calls accessor methods on an entity bean to read the value of every individual data member

15. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Coarse Grained Entity Bean Design Idiom The client uses an entity bean to retrieve a state object populated with database data

16. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Optimized Entity Bean Design Idiom The client uses an entity bean to retrieve a state object populated with database data. The entity bean does not update the data store unless the state has been changed.

17. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Session Over Entity Bean Design Idiom The client uses a session bean to retrieve a state object populated with database data, but the session bean populates the state object based on its conversation with a fine grained entity bean

18. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Coarse Grained Stateless Session Bean Design Idiom The client uses a stateless session bean to retrieve a state object populated with database data

19. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Four Tests Test 1 – designed to measure the relative performance when accessing a single instance of data Test 2 – designed to measure the relative performance when accessing small (up to 100 element) collections of data instances Test 3 – designed to measure the relative performance when accessing large (up to 1,000 element) collections of data instances Test 4 – a load test. Designed to measure relative performance when accessing a collection of 50 data instances by a varying number of clients concurrently.

20. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Benchmark Setup App. Server – JBoss 2.0 with bundled Tomcat 3.2 Database – Hypersonic (bundled with JBoss) Hardware – PIII 600Mhz (mobile) 392Mb RAM Operating System – Windows 2000

21. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 1 (Single Instance Access)

22. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 2

23. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 2 (cont.) (Regression Analysis) The CGS idiom is 121 times faster than the FGE idiom.

24. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 3

25. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 3 (cont.) (Regression Analysis) The CGS idiom is 86 times faster than the FGE idiom.

26. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 4

27. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Results of Test 4 (cont.) (Regression Analysis) The CGE idiom scales 8.67 times better than the OE idiom.

28. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Explanation of Results Single instance access – EJB containers call ejbLoad() and ejbStore() methods automatically during transactions. If a method call requires a Transaction, then at least ejbStore() will be called before the Transaction associated with the method call completes, even if there has been no change to the state. Collection access – Entity beans know how to load (restore) only a single instance at a time. No optimizations for bulk access are possible when using Entity beans.

29. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Strategy for Optimized Performance Practice Coarse Grained Access - State objects pattern (aka. Memento, Value Objects). Eliminate superfluous calls to ejbLoad() and ejbStore() – use Session Beans instead of Entity Beans Optimize bulk access – use a single conversation with the database when accessing multiple instances

30. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Beyond Performance: Code that is Simple and Easy to Maintain Introduction to EJBs EJB Performance Benchmark Beyond Performance: Code that is Simple and Easy to Maintain –Remaining problems –Domain Façade as a solution Introduction UML diagram Automatic Primary Key Dereferencing Class = data + behavior Layered and Columnar Architecture Real World Implementation

31. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Remaining Problems EJBs do not provide an elegant solution to automatic primary key dereferencing and object navigation. Coarse grained access patterns do not adhere to Object Oriented Programming principles: class = data + behavior

32. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Introduction to the Domain Façade Idiom Builds on top of the Coarse Grained Session Bean idiom, thus maintains the performance advantage Adds the concepts of Domain Class and Domain Helper: –Domain Class – classes whose instances wrap State object instances –Domain Helper – utility classes that carry on conversations with EJBs

33. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Domain Façade Class Diagram

34. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Automatic Primary Key Dereferencing Example EJBs do not have object references to other EJBs, rather they hold the Primary Keys of referenced instances. Domain Classes provide object references.

35. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. “Class = data + behavior” Example When using Domain Facades, the developer has complete control over which accessor and mutator methods should be available to the client. The developer can also add business methods that express behaviors.

36. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Layered and Columnar Architecture of Domain Facade

37. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Business Logic Settles Close to the Client and Close to the Data Store

38. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. A Detailed View of the Layers Each layer knows only about the layer behind it The loose coupling promotes: –code reuse –ease of maintenance –parallel development

39. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Alamo MPOWERENT Project Online rental management system Available via extranet to insurance company partners Fully integrated with legacy rental system In production since August 2000 Over 8,000 business users App. server on two clustered HP servers running WebLogic 5.1 Average app. server CPU load is under 5%

40. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Further Issues Treatment of dependent objects within the Domain Façade idiom Automatic state validation Non data intense domain classes that do not require the save() method

41. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Summary EJB Performance –EJB Performance Benchmark –Lessons Learned / Strategy for Optimized Performance –Turning Strategy into a Design Beyond Performance: Code that is Simple and Easy to Maintain –Remaining Problems – Absence of OOP –Domain Façade as a Solution

42. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Thank you! Maciej Zawadzki mbz@urbancode.com

43. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Benefits of Domain Façades Performance – built on top of best performing idiom Maintenance – layered architecture allows updates to any one layer to be isolated from all above layers. Columnar architecture makes updates to any one Domain column easy as all Domain related concepts (Domain Class and Helper, EJB, DAO) are isolated from any other Domain columns. Ease of Development –Automatic Primary Key dereferencing makes code more readable and bug free. –Ability to combine logic with data in adherence with OOP brings in all advantages of OOP.

44. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. EJB Broker Pattern

45. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Persistence Services EJB Pattern

46. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Domain Classes in Detail Private reference to a corresponding state object Constructor – accepts a state object –Called either for a restored instance, or –When a new instance is created Wrapping simple fields –Accessor calls are delegated to the state object –Mutator calls are delegated to the state object

47. Copyright  2001 Urbancode Software Development, Inc. All Rights Reserved. Domain Classes in Detail (cont.) Wrapping reference fields –Accessor calls are intercepted. The PK of the referenced object is obtained from the state object. The PK is then converted into a Domain Class reference by calling a lookup method on the associated Helper. The Domain Class reference may be cached for later usage. –Mutator calls are intercepted. The PK of the Domain Class parameter is obtained and set on the state object. The Domain Class reference may be cached for later usage. The save() method –Calls the serviceState(…) method on the associated Helper with the state object as a parameter. The method returns an updated state object which then becomes the new state.