Add the C, CPP, JavaRS, KotlinC, KotlinSync, PHP, Ruby Getting Started Code

[tmcneil-mdb]

Description

Adds the remaining six Get Started sample applications — C, C++, Java Reactive
Streams, Kotlin Coroutines, Kotlin Sync, PHP, and Ruby — mirroring the existing
go/hello-world, node/hello-world, python/hello-world, dotnet/hello-world,
and java/hello-world samples. Each app connects to a MongoDB deployment using
the connection string in the MONGODB_URI environment variable, seeds a few
sample product documents into the get_started.products collection, then
queries and prints one of them.

• c/hello-world/ — sample app, CMake build (mongoc 2.0), README, .gitignore
• cpp/hello-world/ — sample app, CMake build (mongocxx 4.0), README, .gitignore
• java-rs/hello-world/ — sample app, Maven build (mongodb-driver-reactivestreams via mongodb-driver-bom 5.9.1, Project Reactor 2025.0.0, Java 21), README, .gitignore
• kotlin-coroutine/hello-world/ — sample app, Maven build (mongodb-driver-kotlin-coroutine 5.9.1, Kotlin 2.1.0), README, .gitignore
• kotlin-sync/hello-world/ — sample app, Maven build (mongodb-driver-kotlin-sync 5.9.1, Kotlin 2.1.0), README, .gitignore
• php/hello-world/ — sample app, Composer manifest (mongodb/mongodb 2.0, ext-mongodb 2.0), README, .gitignore
• Added the C, C++, Java Reactive Streams, Kotlin Coroutines, Kotlin Sync, and PHP,
  entries to the root README

This supersedes the following PRs, which targeted the wrong repository:

• DOCSP-61799: C Getting Started mongodb-code-examples#6 (C)
• DOCSP-61800: CPP Getting Started mongodb-code-examples#7 (C++)
• DOCSP-61803: JavaRS Getting Started mongodb-code-examples#8 (Java Reactive Streams)
• DOCSP-61805: Kotlin Coroutine Getting Started mongodb-code-examples#9 (Kotlin Coroutines)
• DOCSP-61806: Kotlin Sync Getting Started mongodb-code-examples#10 (Kotlin Sync)
• DOSCP-61807: PHP Getting Started mongodb-code-examples#11 (PHP)

README changes

• Added Windows commands throughout

Testing

All six samples were run end to end on macOS by following the documented
setup steps in each README, connecting to an Atlas deployment and confirming
the expected product document was printed.

JIRA

• DOCSP-61799 — C
• DOCSP-61800 — C++
• DOCSP-61803 — Java Reactive Streams
• DOCSP-61805 — Kotlin Coroutines
• DOCSP-61806 — Kotlin Sync
• DOCSP-61807 — PHP

[Copilot]

Pull request overview

Adds six MongoDB getting-started samples across C, C++, Java Reactive Streams, Kotlin, and PHP. Ruby is advertised but not implemented.

Changes:

• Adds sample applications that seed and query products.
• Adds build manifests, setup guides, and ignore rules.
• Expands the root client-library index.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
README.md	Adds client-library links.
c/hello-world/README.md	Documents C setup and usage.
c/hello-world/hello-world.c	Implements the C sample.
c/hello-world/CMakeLists.txt	Configures the C build.
c/hello-world/.gitignore	Ignores C build output.
cpp/hello-world/README.md	Documents C++ setup and usage.
cpp/hello-world/main.cpp	Implements the C++ sample.
cpp/hello-world/CMakeLists.txt	Configures the C++ build.
cpp/hello-world/.gitignore	Ignores C++ build output.
java-rs/hello-world/README.md	Documents reactive Java usage.
java-rs/hello-world/src/main/java/HelloWorld.java	Implements the reactive Java sample.
java-rs/hello-world/pom.xml	Configures Java dependencies and execution.
java-rs/hello-world/.gitignore	Ignores Maven output.
kotlin-coroutine/hello-world/README.md	Documents coroutine sample usage.
kotlin-coroutine/hello-world/src/main/kotlin/HelloWorld.kt	Implements the coroutine sample.
kotlin-coroutine/hello-world/pom.xml	Configures coroutine dependencies and build.
kotlin-coroutine/hello-world/.gitignore	Ignores Maven output.
kotlin-sync/hello-world/README.md	Documents Kotlin Sync usage.
kotlin-sync/hello-world/src/main/kotlin/HelloWorld.kt	Implements the Kotlin Sync sample.
kotlin-sync/hello-world/pom.xml	Configures Kotlin Sync dependencies and build.
kotlin-sync/hello-world/.gitignore	Ignores Maven output.
php/hello-world/README.md	Documents PHP setup and troubleshooting.
php/hello-world/src/HelloWorld.php	Implements the PHP sample.
php/hello-world/composer.json	Declares PHP dependencies.
php/hello-world/.gitignore	Ignores PHP-generated files.

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[mongoKart]

Claude feedback! Also kicked off a Copilot review.

[mongoKart]

System.getenv("MONGODB_URI") is passed straight to MongoClients.create(uri) with no null check; if the user skips the export MONGODB_URI step (the exact failure the README tells them to check for), the app dies with a raw NPE/IllegalArgumentException stack trace instead of the friendly message the C, C++, and PHP versions print.

[mongoKart]

product.toJson() derefs the result of find(...).first() unguarded; the Kotlin siblings use product?.toJson(). If the insert is silently filtered (e.g. a stale/different get_started.products state or a name mismatch), this is an NPE rather than "no output".

[mongoKart]

same unchecked System.getenv("MONGODB_URI") passed to MongoClient.create(uri); missing-env-var case fails with an opaque exception instead of the guarded message used in the other languages.

[mongoKart]

same unchecked System.getenv("MONGODB_URI") passed to MongoClient.create(uri); missing-env-var case fails with an opaque exception instead of the guarded message used in the other languages.

[mongoKart]

products.delete_many({}) and insert_many(...) return values are discarded and find_one failure falls through with no output at all; combined with no else branch, a failed seed prints nothing and exits EXIT_SUCCESS, so the README's "verify MONGODB_URI" advice is the only signal a user gets.