polish some code

[JaredTan95]

What's the purpose of this PR

polish some gson code.

[codecov-commenter]

Codecov Report

Merging #3249 into master will increase coverage by 0.01%.
The diff coverage is 74.62%.

@@             Coverage Diff              @@
##             master    #3249      +/-   ##
============================================
+ Coverage     51.47%   51.48%   +0.01%     
- Complexity     2294     2304      +10     
============================================
  Files           442      442              
  Lines         13739    13733       -6     
  Branches       1398     1397       -1     
============================================
- Hits           7072     7071       -1     
+ Misses         6176     6173       -3     
+ Partials        491      489       -2     

Impacted Files	Coverage Δ	Complexity Δ
...trip/framework/apollo/biz/service/ItemService.java	15.06% <0.00%> (+0.40%)	4.00 <0.00> (ø)
...ramework/apollo/openapi/util/OpenApiBeanUtils.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...mework/apollo/portal/component/PortalSettings.java	65.62% <0.00%> (ø)	5.00 <0.00> (ø)
...mework/apollo/portal/spi/ctrip/CtripMQService.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ramework/apollo/portal/service/ReleaseService.java	5.61% <25.00%> (ø)	2.00 <1.00> (ø)
...k/apollo/portal/component/config/PortalConfig.java	22.82% <33.33%> (ø)	9.00 <0.00> (ø)
...inservice/controller/ReleaseHistoryController.java	25.00% <50.00%> (ø)	2.00 <1.00> (+1.00)
...m/ctrip/framework/apollo/biz/config/BizConfig.java	26.78% <50.00%> (ø)	8.00 <1.00> (ø)
...p/framework/apollo/portal/service/ItemService.java	47.87% <50.00%> (ø)	17.00 <1.00> (+1.00)
...k/apollo/portal/service/ReleaseHistoryService.java	7.46% <50.00%> (ø)	2.00 <1.00> (+1.00)
... and 16 more

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[nobodyiam]

LGTM