Update DubboCodec.java

[linhuaichuan]

fix issue #3537: 新旧版本兼容问题

Brief changelog

dubbo 反序列化对分片流操作时的兼容性支持

Verifying this change

1、DubboCodec 解码时，对is流进行多次操作

            ObjectInput in = CodecSupport.deserialize(channel.getUrl(), is, proto);
            if (status == Response.OK) {
                Object data;
                if (res.isHeartbeat()) {
                    data = decodeHeartbeatData(channel, in);
                } else if (res.isEvent()) {
                    data = decodeEventData(channel, in);
                } else {
                    DecodeableRpcResult result;
                    if (channel.getUrl().getParameter(
                            Constants.DECODE_IN_IO_THREAD_KEY,
                            Constants.DEFAULT_DECODE_IN_IO_THREAD)) {
                        result = new DecodeableRpcResult(channel, res, is,
                                (Invocation) getRequestData(id), proto);
                        result.decode();
                    } else {
                        result = new DecodeableRpcResult(channel, res,
                                new UnsafeByteArrayInputStream(readMessageData(is)),
                                (Invocation) getRequestData(id), proto);
                    }
                    data = result;
                }
                res.setResult(data);

2、当序列化工具使用分片读取is时，将造成result.decode()解码错误;比如fst.

[codecov-io]

Codecov Report

Merging #3568 into 2.6.x will decrease coverage by 0.07%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##              2.6.x    #3568      +/-   ##
============================================
- Coverage     47.12%   47.04%   -0.08%     
+ Complexity     4392     4389       -3     
============================================
  Files           565      565              
  Lines         25088    25091       +3     
  Branches       4422     4422              
============================================
- Hits          11823    11805      -18     
- Misses        11436    11458      +22     
+ Partials       1829     1828       -1

Impacted Files	Coverage Δ	Complexity Δ
...m/alibaba/dubbo/rpc/protocol/dubbo/DubboCodec.java	58.41% <33.33%> (-1.79%)	13 <0> (ø)
...aba/dubbo/remoting/transport/mina/MinaChannel.java	42.25% <0%> (-11.27%)	15% <0%> (-1%)
.../remoting/transport/netty4/NettyServerHandler.java	72.22% <0%> (-11.12%)	6% <0%> (-1%)
...om/alibaba/dubbo/rpc/filter/ActiveLimitFilter.java	77.77% <0%> (-5.56%)	5% <0%> (-1%)
...a/dubbo/remoting/transport/netty/NettyChannel.java	61.25% <0%> (-5%)	20% <0%> (-1%)
.../com/alibaba/dubbo/monitor/dubbo/DubboMonitor.java	87.85% <0%> (-1.87%)	15% <0%> (ø)
...a/dubbo/remoting/transport/netty4/NettyClient.java	64.4% <0%> (+1.69%)	11% <0%> (+1%)	⬆️
...onfig/spring/extension/SpringExtensionFactory.java	78.37% <0%> (+2.7%)	9% <0%> (ø)	⬇️

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[lovepoem]

@linhuaichuan Can you please add some unit test or integration test to verify the change ?

[linhuaichuan]

@lovepoem
1、CodecSupport.deserialize 反序列化 is ，当序列化工具使用分片读流时，若RpcResult的序列化byte大于分片值时，将引起is的startIndex变动。比如fst工具：org.nustaq.serialization.util.FSTInputStream 默认使用 8000 byte 分片读取is。

2、result.decode() 这时在反序列is。若startIndex产生变动，将引起RpcResult 读取到的序列化byte不正确。最终可能产生 #3537 issue。

[limingwei]

哇哈哈
所以
要解决了么？
什么时候发？

[beiwei30]

this change looks reasonable, but it will not solve issue #3537.

[beiwei30]

I will port your change into main trunk with this: #3991. Once it's in, I will merge your change too. @linhuaichuan

[qixiaobo]

The same issue with #4612
Why nobody takes care of old stable version like 2.6.x?

[qixiaobo]

Another place also has this code
Why not modify all?

[CLAassistant]

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[AlbumenJ]

@linhuaichuan hi, thanks for your contribution

pls resolve conflicts with the latest master branch

[AlbumenJ]

Close for long time no response.
Please feel free to reopen if you have any question.