feat(java): add TCP/TLS integration tests and examples

[atharvalade]

Which issue does this PR close?

Closes #2805

Rationale

The Java SDK had TLS builder methods but no integration tests connecting to a TLS server and no TLS examples.

What changed?

Existing tests only verified TLS builder method chaining but never actually connected to a TLS server.

Added TlsConnectionTest integration test using Testcontainers with TLS certificates mounted from core/certs/. Tests cover: TLS connection with CA cert, TLS connection with server cert, plain TCP failure when TLS is required, and full send/receive message flow over TLS. Added TcpTlsProducer and TcpTlsConsumer examples using IggyTcpClient.builder().enableTls().tlsCertificate(...).

Local Execution

Passed. spotlessCheck and compileJava/compileTestJava clean in both examples/java and foreign/java.

AI Usage

1. Opus 4.6
2. guided by existing GettingStarted examples, BaseIntegrationTest, and C# TLS test patterns
3. Compiled and linted locally, verified code follows existing patterns exactly
4. Yes

[atharvalade]

Resolved

[mmodzelewski]

WIP

It's best if you mark WIP PRs as drafts — that way it's clearly visible from the list that they're not pending maintainer action.

[atharvalade]

WIP

It's best if you mark WIP PRs as drafts — that way it's clearly visible from the list that they're not pending maintainer action.

Will keep that in mind. Though these issues aren't WIP anymore. I'll update the comments.

[mmodzelewski]

Cheers @atharvalade. I'll have a proper look at this later. Just a quick note - could you include these examples in the README? They're picked up by the run-java-examples-from-readme.sh script in the CI. Unless they're actually executed as part of the build, they’ll likely become outdated quite fast.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.07%. Comparing base (5d3b793) to head (40c0425).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2823      +/-   ##
============================================
- Coverage     70.11%   70.07%   -0.04%     
  Complexity      776      776              
============================================
  Files          1028     1028              
  Lines         85279    85279              
  Branches      62654    62665      +11     
============================================
- Hits          59792    59758      -34     
- Misses        22963    22984      +21     
- Partials       2524     2537      +13     

Flag	Coverage Δ
csharp	67.45% <ø> (-0.17%)	⬇️
go	36.37% <ø> (ø)
java	56.26% <ø> (ø)
node	91.37% <ø> (-0.07%)	⬇️
python	81.43% <ø> (ø)
rust	70.64% <ø> (-0.04%)	⬇️

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see 14 files with indirect coverage changes

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[atharvalade]

Cheers @atharvalade. I'll have a proper look at this later. Just a quick note - could you include these examples in the README? They're picked up by the run-java-examples-from-readme.sh script in the CI. Unless they're actually executed as part of the build, they’ll likely become outdated quite fast.

@mmodzelewski added!