1. Developing and testing enterprise Java applications
Chris Richardson
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

2. Copyright (c) 2005 Chris Richardson. All rights reserved.
Who am I?
Twenty years of software development experience
Building object-oriented software since 1986
Developing with Java since 1996
Author of POJOs in Action
Run a consulting company that helps organizations develop software more effectively
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

3. Copyright (c) 2005 Chris Richardson. All rights reserved.
Key points
EJBs are (mostly) a bad idea
Plain Old Java Objects and lightweight frameworks make development easier and faster
Don’t access the DB if you want thorough tests that execute quickly
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

4. Copyright (c) 2005 Chris Richardson. All rights reserved.
Agenda
Overview of enterprise Java
Developing with POJOs and lightweight frameworks
Effective testing strategies
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

5. Copyright (c) 2005 Chris Richardson. All rights reserved.
J2EE architecture
Client
Server
From J2EE spec
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

6. Copyright (c) 2005 Chris Richardson. All rights reserved.
EJB strengths
It’s the standard for building object-oriented, distributed applications in Java
Declarative transactions and security
Truly distributed applications where EJBs participate in transactions initiated by a remote client
Messaging-oriented applications that can benefit from message-driven beans
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

7. Copyright (c) 2005 Chris Richardson. All rights reserved.
EJBs weaknesses
But most applications don’t need distributed transactions initiated by a remote client
Code is coupled to the server container
Long edit-compile-debug cycles
Slow development and testing
Excessive complexity
Complicated XML descriptor files
Complicated IDE requirements
EJB encourage procedural programming and make object-oriented programming difficult
Broken object/relational mapping
EJB 3 fixes some things but …
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

8. Copyright (c) 2005 Chris Richardson. All rights reserved.
Agenda
Overview of enterprise Java
Developing with POJOs and lightweight frameworks
Effective testing strategies
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

9. The solution: POJOs = Plain Old Java Objects
Java objects that don't implement any special interfaces
Coined by Fowler to make it sound just as exciting as JavaBeans, Enterprise JavaBeans
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

10. Simple idea with surprising benefits
Simpler development
Test without an application server
Business logic and persistence are separate
Faster development
Test without deploying
Easier testing
More maintainable
Modular object-oriented code
Loosely coupled design
Decouple technologies from core business logic
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

11. Copyright (c) 2005 Chris Richardson. All rights reserved.
Persisting POJOs
 Object/relational mapping framework
Hibernate
Very popular open-source project
JDO
Standard from Sun – JSR 12 and JSR 243
Multiple implementations: Kodo JDO, Versant, JPOX
EJB 3/JSR 220 persistence
Intended to be “the” standard Java persistence mechanism
But it has limitations, …
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

12. ORM framework features
Declarative mapping
CRUD API
Query language
Transaction management
Lazy and eager loading
Caching
Detached objects
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

13. Making POJOs transactional
An easy to use solution is the Spring framework
Popular open-source framework for simplifying J2EE development
Lightweight container for POJOs
Provides declarative transactions for POJOs
Makes it easier to use JDO and Hibernate
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

14. Spring lightweight container
Lightweight container = sophisticated factory for creating objects
Spring bean = object created and managed by Spring
You write XML that specifies how to create and initialize the objects
Lightweight container can wrap an object with a proxy
Proxy masquerades as the original object
Proxy executes arbitrary code before and after method call
Spring uses proxies for:
transaction management
Security …
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

15. Copyright (c) 2005 Chris Richardson. All rights reserved.
Agenda
Overview of enterprise Java
Developing with POJOs and lightweight frameworks
Effective testing strategies
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

16. POJO application design
POJO facade
Domain model
Database access
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

17. Copyright (c) 2005 Chris Richardson. All rights reserved.
Testing overview
Challenge
You need lots of tests (at every level)
You want the tests to run quickly
Databases are slow
Solution
Test without the database where possible
Use an in-memory database such as HSQLDB
Without a database (fast)
Test the business logic and repositories with mock objects
Test the object/relational mapping
With a database (slow)
CRUD tests for persistent objects
Test the queries
With a database (fast)
Test the database schema
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

18. Testing the domain model
Goal:
Test the business logic
Top-down, test-driven development
Service => Domain entity,…
How:
Use fast, easy to write, in-memory tests
Use mocks for an object’s collaborators
Especially the repositories, which access the DB
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

19. Mock object tests for the repositories
Repository = domain model class that wraps the ORMF
Problem:
Bugs in the logic of the repositories
Testing against the DB is slow
Solution
Use mock objects for the ORMF APIs
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

20. Test the object/relational mapping
Problem:
Incorrectly defined mapping, e.g. forgetting to map a field is a common bug
But tests that save objects and check the contents of the DB are slow to execute and tedious to write
Solution:
Read XML or metadata
Make assertions about the mapping
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

21. Copyright (c) 2005 Chris Richardson. All rights reserved.
Testing the schema
Problem:
Object/relational mapping can reference non-existent tables and columns
Only some execution paths will access those tables and columns
Solution
Write a test that verifies that all referenced tables and columns exists
How
Persistence framework-specific
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

22. CRUD tests for the persistent objects
Problem:
Database constraints can prevent application from updating the database
Solution
Verify that the objects can be created, updated and deleted
Each test takes an object through its lifecycle
Creates and saves an object
One or more times: Load and update it
Delete the object
These tests are slow
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

23. Copyright (c) 2005 Chris Richardson. All rights reserved.
Testing queries
Problem:
Malformed queries
Logic errors in queries, e.g. < instead of <=
Solution:
Write tests for the queries
Each test:
Populates database with test objects
Execute queries with parameters
Verify that the query returns the expected result
These tests can be slow
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

24. Copyright (c) 2005 Chris Richardson. All rights reserved.
Testing the façade
Façade = encapsulates the business logic
Mock object tests
Mock the domain objects called by the facade
Integration tests:
Façade is a good place to test the business tier independently of the UI
Write tests for the façade that access the database
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

25. Copyright (c) 2005 Chris Richardson. All rights reserved.
Summary
Use POJOs and lightweight frameworks instead of EJB
Test at every level
Test without the database as much as possible
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.

26. Copyright (c) 2005 Chris Richardson. All rights reserved.
For more information
Blog:
My book (4Q05):
POJOs in Action
4/7/2019
Copyright (c) Chris Richardson. All rights reserved.