Best practices: use final wherever possible, constructor injection, this. access to fields

[krasa]

Implementation of following best practices:

Every class should be final by default, except classes explicitly designed to be extensible. Unfortunately Spring beans cannot be final - http://stackoverflow.com/questions/2657432/make-spring-service-classes-final
Also method and constructor parameters, field and variables should be final. This is a no-brainer.

It is recommended to use constructor injection instead of field injection to provide better testability and safety against NPE. Every object should be fully initialized upon construction.

Using .this to access fields provide a safety against accidental use of parameter/variable, thus greatly reducing a number of possible bugs..

Supersedes: #153 #172

Resources:
http://whiley.org/2011/12/06/final-should-be-default-for-classes-in-java

[krasa]

Also contains some minor correctness fixes, and a context holder for integration of beans with static utility classes - it might be wise to change them into beans in future.

[mikkelee]

+1

[emiln]

I think this is a very valuable and needed contribution to the FizzBuzzEnterpriseEdition project, but it currently seems to be failing our comprehensive test suite on Travis CI. I will be happy to merge it as soon as it is back to passing our tests.

[krasa]

thank you, interesting that this commit caused it: krasa@a7c7d84 :)
lets try rebuild....

[codecov-io]

Current coverage is 85.43%

Merging #191 into master will change coverage by +1.44% by e433120

Coverage Diff

@@            master    #191   diff @@
======================================
  Files           59      60     +1
  Stmts          281     357    +76
  Branches        21      21       
  Methods          0       0       
======================================
+ Hit            236     305    +69
  Partial          7       7       
- Missed          38      45     +7

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[emiln]

I've requested a new build on Travis CI. It should start shortly.