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 Unless they're actually executed as part of the build, they’ll likely become outdated quite fast.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 71.89%. Comparing base (514b5c5) to head (eb7bfa3).
⚠️ Report is 30 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2823      +/-   ##
============================================
+ Coverage     71.44%   71.89%   +0.44%     
- Complexity      708      739      +31     
============================================
  Files           969      988      +19     
  Lines         78219    80173    +1954     
  Branches      60029    61308    +1279     
============================================
+ Hits          55884    57638    +1754     
- Misses        20002    20170     +168     
- Partials       2333     2365      +32     

Flag	Coverage Δ
csharp	67.43% <ø> (+0.18%)	⬆️
java	54.83% <ø> (+0.81%)	⬆️
node	92.26% <ø> (-0.15%)	⬇️
python	81.57% <ø> (?)
rust	70.04% <ø> (+0.48%)	⬆️

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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!