Add the BT Connector for Flink 2.1

[techienidhipatel]

Upgrade Bigtable Connector to Apache Flink 2.1

Fixes # (no existing issue - opening PR for discussion)

Summary

This PR upgrades the Flink Bigtable connector from Apache Flink 1.20.0 to 2.1.0, ensuring compatibility with the latest Flink 2.x series released in December 2025.

Changes Made

1. Core API Updates

• Removed deprecated Sink.InitContext (BigtableSink.java)
  • Deleted the createWriter(Sink.InitContext) method which was already deprecated and throwing UnsupportedOperationException
  • The connector now uses only createWriter(WriterInitContext) which is the supported API in Flink 2.x
  • Reference: Flink 2.0 API Evolution

2. Version Upgrade

• Updated Flink dependency from 1.20.0 to 2.1.0 in pom.xml

3. Example Code Fixes

• Fixed import paths in all 8 example files to reflect Flink 2.0 package restructuring:
  • Changed: org.apache.flink.api.java.utils.ParameterTool
  • To: org.apache.flink.util.ParameterTool
  • Affected files:
    • WriteExactlyOnce.java
    • WriteGenericRecord.java
    • WriteGenericRecordNested.java
    • WriteRowData.java
    • WriteRowDataNested.java
    • WriteTableAPI.java
    • WriteTableAPINested.java
    • WriteWithFunction.java

4. Shaded JAR Configuration

• Added shade-pom.xml for building a self-contained connector JAR
  • Bundles all Google Cloud dependencies
  • Relocates packages to avoid conflicts with Flink's internal libraries
  • Excludes Flink runtime dependencies (marked as provided)
  • Follows the same pattern as other Flink connectors

Testing

• All 55 existing tests pass
• Compiled successfully with Flink 2.1.0
• Examples compile without errors
• Shaded JAR builds successfully (63MB with all dependencies)
• Tested locally with Flink 2.1 cluster writing to Bigtable staging instance

Compatibility Notes

• Breaking Changes: None for end users - the connector API remains the same
• Minimum Flink Version: Now requires Flink 2.1.0 or later
• Java Version: Continues to support Java 11+ (as per parent POM)

Checklist

• Tests pass
• Code follows existing style and conventions
• Examples updated and functional
• No documentation changes needed (connector usage remains the same)
• Shaded JAR configuration added for easier deployment

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