bugfix: support jdk9+ compile code

[funky-eyes]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Merging #6085 (347f2eb) into 2.x (e32cb1c) will decrease coverage by 0.06%.
The diff coverage is 37.50%.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6085      +/-   ##
============================================
- Coverage     49.55%   49.50%   -0.06%     
+ Complexity     4763     4760       -3     
============================================
  Files           908      909       +1     
  Lines         31375    31390      +15     
  Branches       3782     3782              
============================================
- Hits          15549    15540       -9     
- Misses        14289    14312      +23     
- Partials       1537     1538       +1     

Files	Coverage Δ
...atasource/undo/parser/ProtostuffUndoLogParser.java	55.71% <100.00%> (ø)
...ava/io/seata/serializer/seata/SeataSerializer.java	80.00% <100.00%> (ø)
...in/java/io/seata/server/session/BranchSession.java	79.45% <100.00%> (ø)
...in/java/io/seata/server/session/GlobalSession.java	72.96% <100.00%> (ø)
...torage/file/store/FileTransactionStoreManager.java	56.27% <100.00%> (ø)
.../seata/serializer/protobuf/ProtobufSerializer.java	0.00% <0.00%> (ø)
...rc/main/java/io/seata/common/util/BufferUtils.java	0.00% <0.00%> (ø)

... and 5 files with indirect coverage changes

[wangliang181230]

LGTM