make ConfigChangeEvent immutable

[wanghbxxxx]

What is the purpose of the change

XXXXX

Brief changelog

XXXXX

Verifying this change

XXXXX

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[carryxyh]

I don't think this is necessary. Make the field of ConfigChangeEvent final has the same effect as this pr.

[carryxyh]

Let's focus on your another pr:
#3398

[wanghbxxxx]

I don't think this is necessary. Make the field of ConfigChangeEvent final has the same effect as this pr.

make the filed final wont stop invoker change the properties of event,
for instance: event.setKey("")

[codecov-io]

Codecov Report

Merging #3399 into master will increase coverage by 0.09%.
The diff coverage is 36.36%.

@@             Coverage Diff              @@
##             master    #3399      +/-   ##
============================================
+ Coverage     63.75%   63.85%   +0.09%     
  Complexity       71       71              
============================================
  Files           661      661              
  Lines         28602    28600       -2     
  Branches       4806     4821      +15     
============================================
+ Hits          18236    18262      +26     
+ Misses         8134     8118      -16     
+ Partials       2232     2220      -12

Impacted Files	Coverage Δ	Complexity Δ
...stry/integration/AbstractConfiguratorListener.java	30.76% <0%> (ø)	0 <0> (ø)	⬇️
...apache/dubbo/rpc/cluster/router/tag/TagRouter.java	39.5% <0%> (ø)	0 <0> (ø)	⬇️
...ster/router/condition/config/ListenableRouter.java	33.33% <0%> (ø)	0 <0> (ø)	⬇️
...ter/support/apollo/ApolloDynamicConfiguration.java	0% <0%> (ø)	0 <0> (ø)	⬇️
.../configcenter/support/zookeeper/CacheListener.java	68.42% <100%> (ø)	0 <0> (ø)	⬇️
...e/dubbo/configcenter/DefaultConfigChangeEvent.java	43.75% <43.75%> (ø)	0 <0> (?)
...che/dubbo/remoting/transport/mina/MinaChannel.java	43.42% <0%> (-10.53%)	0% <0%> (ø)
...ng/exchange/support/header/HeartbeatTimerTask.java	73.68% <0%> (-5.27%)	0% <0%> (ø)
...che/dubbo/common/compiler/support/JdkCompiler.java	64.54% <0%> (ø)	0% <0%> (ø)	⬇️
... and 18 more

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[carryxyh]

My fault.
I mean make the field final and then delete the setter methods.

[wanghbxxxx]

i

My fault.
I mean make the field final and then delete the setter methods.

ok, i will send another pr later, thank you