[BEAM-8471] Put back FlinkJobServerDriver.fromParams to fix post commit

[tweise]

https://builds.apache.org/job/beam_PostCommit_Java_PVR_Flink_Streaming/lastCompletedBuild/testReport/org.apache.beam.sdk/PipelineTest/testTupleInjectionTransform/

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Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---		---	---
Java
Python		---			---	---
XLang	---	---	---		---	---	---

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website
Non-portable
Portable	---		---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

[tweise]

follow-up from #9872

[tweise]

Run Java Flink PortableValidatesRunner Streaming

[ibzib]

Any reason we can't change TestPortableRunner to use a proper interface, ie JobServerDriver? It'd definitely be less fragile than a reflection-based pseudo-interface.

[tweise]

Any reason we can't change TestPortableRunner to use a proper interface, ie JobServerDriver? It'd definitely be less fragile than a reflection-based pseudo-interface.

Definitely worthwhile to investigate as follow-up. I don't like that fromXXX spaghetti and was trying to reduce it a bit. Will still need reflection to instantiate the class though.

[ibzib]

Will still need reflection to instantiate the class though.

Right, but we could add fromParams to the JobServerDriver interface. Then in TestPortableRunner we could narrow from Object to JobServerDriver.

[ibzib]

Anyway, your changes LGTM. I don't think we need to change too much to improve the interface stuff, but if you don't want to do that here I can do it in a follow-up.

[tweise]

Anyway, your changes LGTM. I don't think we need to change too much to improve the interface stuff, but if you don't want to do that here I can do it in a follow-up.

Go for it. What I did was to make something else work, it would be good to do a focussed cleanup.

[ibzib]

Filed https://issues.apache.org/jira/browse/BEAM-8509 as a follow-up.