Unit test of JValidator; Clean code of JValidator

[tswstarplanet]

What is the purpose of the change

Add unit test of JValidator; clean code of JValidator

Brief changelog

1.JValidatorTest and relative test class
2.JValidator

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3723 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master   #3723      +/-   ##
===========================================
- Coverage      63.6%   63.6%   -0.01%     
  Complexity       71      71              
===========================================
  Files           703     703              
  Lines         31001   31000       -1     
  Branches       5022    5022              
===========================================
- Hits          19719   19718       -1     
+ Misses         9016    9014       -2     
- Partials       2266    2268       +2

Impacted Files	Coverage Δ	Complexity Δ
...bbo/validation/support/jvalidation/JValidator.java	79.87% <100%> (+8.9%)	0 <0> (ø)	⬇️
.../apache/dubbo/remoting/transport/AbstractPeer.java	58.69% <0%> (-8.7%)	0% <0%> (ø)
...apache/dubbo/common/config/ConfigurationUtils.java	64% <0%> (-8%)	0% <0%> (ø)
...ava/org/apache/dubbo/config/DubboShutdownHook.java	75% <0%> (-6.25%)	0% <0%> (ø)
...ng/exchange/support/header/HeartbeatTimerTask.java	73.68% <0%> (-5.27%)	0% <0%> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	57.64% <0%> (-4.71%)	0% <0%> (ø)
...dubbo/remoting/exchange/support/DefaultFuture.java	73.46% <0%> (-2.05%)	0% <0%> (ø)
...che/dubbo/remoting/transport/mina/MinaChannel.java	53.94% <0%> (-1.32%)	0% <0%> (ø)
.../exchange/support/header/HeaderExchangeServer.java	66.98% <0%> (-0.95%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	80.7% <0%> (-0.4%)	0% <0%> (ø)
... and 2 more

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[lixiaojiee]

lt looks good to me.