[Feature Request]: Implement JsonIO.read() / readRows() for the Java SDK #40086

What would you like to happen?

Motivation

The Java JsonIO connector (sdks/java/io/json/.../JsonIO.java) currently supports only writing withJsonIO.write() and JsonIO.writeRows(). There is no read path. The connector's own class Javadoc acknowledges this gap:

"Reading from JSON files is not yet implemented in Java. Please see
#24552."

That linked issue (#24552) is actually titled "Implement CsvIO.Read" and is closed as not planned, CsvIO.Read was subsequently implemented under a different path, so there is currently no live tracking issue for JSON reading, and the Javadoc reference is stale. This issue is intended to be that tracking issue.

Proposal

Add a read/parse surface to JsonIO symmetric to the existing write surface
and mirroring the pattern CsvIO already established:

JsonIO.parse(Class<T> klass)      // JSON records -> user type T
JsonIO.parseRows(Schema schema)   // JSON records -> Row

modeled on CsvIO.parse(Class, CSVFormat) (CsvIO.java:419) and CsvIO.parseRows(Schema, CSVFormat) (CsvIO.java:497), including their CsvIOParse result-and-error-handling pattern.

Why this is tractable

The core JSON→Row conversion already exists and is reusable:

• JsonUtils.getJsonStringToRowFunction(Schema)
  (sdks/java/core/.../schemas/utils/JsonUtils.java:104)
• JsonUtils.getJsonBytesToRowFunction(Schema) (line 93)
• JsonUtils.beamSchemaFromJsonSchema(String) (line 201)

The work is primarily wiring these into a read PTransform over FileIO.match() + line reading, following the CsvIO parse structure not new parsing logic.

Testing plan

• Unit tests mirroring CsvIO parse tests: schema validation, type conversion to both Row and custom user classes, error/failure routing.
• Round-trip test: write JSON via JsonIO.write(), read it back via JsonIO.parseRows(), assert equality.
• No new dependencies- JSON schema/parse machinery is already in sdks/java/core.

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam YAML
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Infrastructure
• Component: Spark Runner
• Component: Flink Runner
• Component: Prism Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner