[GitHub] [dubbo] shadowmind opened issue #5389: Dubbo 2.6.x RpcContext.getServerContext().getAttachment(key) is null when consumer use generic

["shadowmind (GitHub)" <gi...@apache.org>]

- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.6.x
* Operating System version: MacOS 10.12.6 
* Java version: Java 1.8

### Steps to reproduce this issue

1. Build a provider demo, add RpcContext.getServerContext().setAttachment("key","value");
2. Build a consumer demo. Call provider service by generic.
3. RpcContext.getServerContext().getAttachment("key");

What do you expected from the above steps？
Get the value which provider set in the RpcContext.getServerContext() attachment

What actually happens?
Null. Can't get the value which provider set in the RpcContext.getServerContext() attachment

Cause:
GenericFilter return a new RpcResult without setting setAttachments

Code(GenericFilter.java):
`Result result = invoker.invoke(new RpcInvocation(method, args, inv.getAttachments()));
                if (result.hasException()
                        && !(result.getException() instanceof GenericException)) {
                    return new RpcResult(new GenericException(result.getException()));
                }
                if (ProtocolUtils.isJavaGenericSerialization(generic)) {
                    try {
                        UnsafeByteArrayOutputStream os = new UnsafeByteArrayOutputStream(512);
                        ExtensionLoader.getExtensionLoader(Serialization.class)
                                .getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
                                .serialize(null, os).writeObject(result.getValue());
                        return new RpcResult(os.toByteArray());
                    } catch (IOException e) {
                        throw new RpcException("Serialize result failed.", e);
                    }
                } else if (ProtocolUtils.isBeanGenericSerialization(generic)) {
                    return new RpcResult(JavaBeanSerializeUtil.serialize(result.getValue(), JavaBeanAccessor.METHOD));
                } else {
                    return new RpcResult(PojoUtils.generalize(result.getValue()));
                }`

Fix:
`RpcResult rpcResult;
                if (ProtocolUtils.isJavaGenericSerialization(generic)) {
                    try {
                        UnsafeByteArrayOutputStream os = new UnsafeByteArrayOutputStream(512);
                        ExtensionLoader.getExtensionLoader(Serialization.class)
                                .getExtension(Constants.GENERIC_SERIALIZATION_NATIVE_JAVA)
                                .serialize(null, os).writeObject(result.getValue());
                        rpcResult = new RpcResult(os.toByteArray());
                    } catch (IOException e) {
                        throw new RpcException("Serialize result failed.", e);
                    }
                } else if (ProtocolUtils.isBeanGenericSerialization(generic)) {
                    rpcResult = new RpcResult(JavaBeanSerializeUtil.serialize(result.getValue(), JavaBeanAccessor.METHOD));
                } else {
                    rpcResult = new RpcResult(PojoUtils.generalize(result.getValue()));
                }
                rpcResult.setAttachments(result.getAttachments());
                return rpcResult;`

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```


[ Full content available at: https://github.com/apache/dubbo/issues/5389 ]
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[GitHub] [dubbo] chickenlj commented on issue #5389: Dubbo 2.6.x RpcContext.getServerContext().getAttachment(key) is null when consumer use generic

["chickenlj (GitHub)" <gi...@apache.org>]

Merged.

[ Full content available at: https://github.com/apache/dubbo/issues/5389 ]
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