This is the project to support the writing of Contracts with the JVM runtime - enabling development of using Java language or other JVM based languages

The Fabric programming model is described in the Developing Applications chapter of the Hyperledger Fabric documentation.

All Contracts should implement ContractInterface interface, in addition to the Contract annotation.

Configuration

Some Java chaincode settings are configurable on a per chaincode basis, including the maximum gRPC inbound message size, thread pool settings, and whether to enable chaincode metrics. The default settings are as follows:

      MAX_INBOUND_MESSAGE_SIZE=104857600
      CHAINCODE_METRICS_ENABLED=false
      TP_CORE_POOL_SIZE=5
      TP_MAX_POOL_SIZE=5
      TP_QUEUE_SIZE=5000
    

To override the defaults, a config.props Java properties file must be included in the default, unnamed, package on your contract code's classpath, which will then be loaded when the chaincode starts. Setting the metrics enabled flag to true will turn on default metrics logging. The TP_ values establish the core thread pool size, max thread poolsize, and the number of of tasks that will wait.

Open Telemetry

To use Open Telemetry, set the following properties:

      CHAINCODE_METRICS_ENABLED=true
      CHAINCODE_METRICS_PROVIDER=org.hyperledger.fabric.metrics.impl.OpenTelemetryMetricsProvider
    

Additionally, you can set properties after the OpenTelemetry specification.
Example:

      OTEL_EXPORTER_OTLP_ENDPOINT=otelcollector:4317
      OTEL_EXPORTER_OTLP_INSECURE=true
    

If you are building your chaincode using Gradle or Maven, create a config.props file in the src/main/resources directory and include the settings you want to override.

Packages

Package	Description
org.hyperledger.fabric	Provides logging classes.
org.hyperledger.fabric.contract	Provides interfaces and classes to support the contract programming model.
org.hyperledger.fabric.contract.annotation	Provides annotations required for Contract implementations.
org.hyperledger.fabric.metrics	Provides interfaces and classes to support collection of metrics.
org.hyperledger.fabric.shim	Provides interfaces and classes required for chaincode development and state variable access.
org.hyperledger.fabric.shim.ext.sbe	Provides an interface for creating and modifying state-based endorsement policies.
org.hyperledger.fabric.shim.ledger	Provides interfaces and classes for querying state variables.
org.hyperledger.fabric.traces	Supports collection of traces