polish code, avoid dup code

[beiwei30]

What is the purpose of the change

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Brief changelog

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Verifying this change

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[codecov-io]

Codecov Report

Merging #3099 into master will decrease coverage by 0.08%.
The diff coverage is 73.61%.

@@             Coverage Diff              @@
##             master    #3099      +/-   ##
============================================
- Coverage     63.58%   63.49%   -0.09%     
  Complexity       75       75              
============================================
  Files           653      653              
  Lines         28210    28208       -2     
  Branches       4794     4791       -3     
============================================
- Hits          17938    17912      -26     
- Misses         8007     8027      +20     
- Partials       2265     2269       +4

Impacted Files	Coverage Δ	Complexity Δ
...in/java/org/apache/dubbo/config/ServiceConfig.java	53.34% <100%> (-0.19%)	0 <0> (ø)
.../java/org/apache/dubbo/config/ReferenceConfig.java	57.69% <100%> (-0.65%)	0 <0> (ø)
...g/apache/dubbo/config/AbstractInterfaceConfig.java	73.26% <73.26%> (-1.82%)	0 <0> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	56.47% <0%> (-5.89%)	0% <0%> (ø)
...he/dubbo/remoting/transport/netty/NettyServer.java	67.85% <0%> (-3.58%)	0% <0%> (ø)
...onfig/spring/extension/SpringExtensionFactory.java	78.04% <0%> (-2.44%)	0% <0%> (ø)
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	77.2% <0%> (-2.21%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	63.04% <0%> (-2.18%)	0% <0%> (ø)
...dubbo/remoting/exchange/support/DefaultFuture.java	71.14% <0%> (-2.02%)	0% <0%> (ø)
...pache/dubbo/remoting/transport/AbstractServer.java	47.91% <0%> (-1.05%)	0% <0%> (ø)
... and 2 more

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[zonghaishang]

Please resolve the code conflict first. @beiwei30