[DUBBO-3537]: dubbox升级dubbo版本的兼容性问题

[beiwei30]

What is the purpose of the change

fix #3537

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3996 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master    #3996      +/-   ##
============================================
- Coverage     63.66%   63.65%   -0.01%     
+ Complexity      566      565       -1     
============================================
  Files           748      748              
  Lines         32309    32311       +2     
  Branches       5134     5135       +1     
============================================
- Hits          20569    20568       -1     
- Misses         9381     9382       +1     
- Partials       2359     2361       +2

Impacted Files	Coverage Δ	Complexity Δ
...src/main/java/org/apache/dubbo/common/Version.java	61.05% <0%> (-1.32%)	0 <0> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	67.39% <0%> (-4.35%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	80.07% <0%> (-1.54%)	0% <0%> (ø)
...che/dubbo/remoting/transport/mina/MinaChannel.java	53.94% <0%> (-1.32%)	17% <0%> (-1%)
...dubbo/remoting/exchange/support/DefaultFuture.java	74.14% <0%> (ø)	0% <0%> (ø)	⬇️
.../java/org/apache/dubbo/config/ReferenceConfig.java	59.85% <0%> (+0.36%)	0% <0%> (ø)	⬇️
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	56.81% <0%> (+11.36%)	0% <0%> (ø)	⬇️

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[kun-song]

合入该 PR 后，Dubbox 和 Dubbo 就可以兼容了吗？ @beiwei30

[chickenlj]

@satansk 要做到和dubbox兼容，恐怕还有一个地方需要做，dubbox直接修改了原生rpc协议编码
https://github.com/dangdangdotcom/dubbox/blob/master/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java#L187

[morisenmen]

我们使用的方案，可供大家参考实现，自定义SPI扩展Codec2，DubboCountCodec，DubboCodec
这两个类，DubboCountCodec引用自定义的DubboCodec，重写encodeResponseData方法，attach判断处理兼容dubbox，本身这个attach判断就是一件兼容处理了dubbox，但是dubbox实现的bug，版本号应该为2.0.0的，invoker的URL传递的是2.8.4，因此这个判断不包含。
扩展实现配置的时候配置自己实现类为dubbo的spi扩展即可
即META-INF/dubbo/internal下面配置扩展[com.alibaba.dubbo/ore.apacha.dubbo].remoting.Codec2
中配置dubbo=自己实现类DubboCountCodec全路径类名即可
该方案只对升级版本的provider做处理，老版本的dubbox完全不需要任何处理
本身可以通过配置实现该功能的，但是dubbo中还有一些bug，可以参考Codec设置的bug说明，我也有备注 #4628
这里还有一个问题，上面写的配置路径不能使用SPI扩展的注解实现，因为这个是替换官方实现的dubbo配置，如果是没有codec设置的bug，则可以使用SPI注解命名，配合ProtocolConfig.setCodec实现，或者配置目录可以是扩展配置路径META-INF/dubbo而不需要再增加internal目录

[neeuq]

@morisenmen 如果在META-INF/dubbo/internal下面配置扩展[com.alibaba.dubbo/ore.apacha.dubbo].remoting.Codec2
中配置dubbo=自己实现类DubboCountCodec全路径类名，是通过java.lang.ClassLoader#getResources来保证自己实现的类优先加载吗？