Hedera™ Hashgraph Java SDK

The Java SDK for interacting with Hedera Hashgraph: the official distributed consensus platform built using the hashgraph consensus algorithm for fast, fair and secure transactions. Hedera enables and empowers developers to build an entirely new class of decentralized applications.

Install

NOTE: v1 of the SDK is deprecated and support will be discontinued after October 2021. Please install the latest version 2.0.x or migrate from v1 to the latest 2.0.x version. You can reference the migration documentation here.

Gradle

Select one of the following depending on your target platform.

// Android, Corda DJVM, Java 7+
implementation 'com.hedera.hashgraph:sdk-jdk7:2.0.8'

// Java 9+, Kotlin
implementation 'com.hedera.hashgraph:sdk:2.0.8'

Select one of the following to provide the gRPC implementation.

// netty transport (for high throughput applications)
implementation 'io.grpc:grpc-netty-shaded:1.38.0'

// netty transport, unshaded (if you have a matching Netty dependency already)
implementation 'io.grpc:grpc-netty:1.38.0'

// okhttp transport (for lighter-weight applications or Android)
implementation 'io.grpc:grpc-okhttp:1.38.0'

Select one of the following to enable or disable Simple Logging Facade for Java (SLFJ4).

// Enable logs
implementation 'org.slf4j:slf4j-simple:1.7.29'

// Disable logs
implementation 'org.slf4j:slf4j-nop:1.7.29'

Maven

Select one of the following depending on your target platform.

<!-- Android, Corda DJVM, Java 7+ -->
<dependency>
  <groupId>com.hedera.hashgraph</groupId>
  <artifactId>sdk-jdk7</artifactId>
  <version>2.0.8</version>
</dependency>

<!-- Java 9+, Kotlin -->
<dependency>
  <groupId>com.hedera.hashgraph</groupId>
  <artifactId>sdk</artifactId>
  <version>2.0.8</version>
</dependency>

Select one of the following to provide the gRPC implementation.

<!-- netty transport (for server or desktop applications) -->
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-netty-shaded</artifactId>
  <version>1.38.0</version>
</dependency>

<!-- netty transport, unshaded (if you have a matching Netty dependency already) -->
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-netty</artifactId>
  <version>1.38.0</version>
</dependency>

<!-- okhttp transport (for lighter-weight applications or Android) -->
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-okhttp</artifactId>
  <version>1.38.0</version>
</dependency>

Usage

Examples of several potential use cases and workflows are available within the repository in examples/.

• Create Account

• Transfer Hbar

• Hedera Consensus Service (HCS)

Development

Dependencies

• Java Development Kit (JDK) v14+ (note this is to build, not run)

Compile

$ ./gradlew compileJava

Unit Test

$ ./gradlew test

Integration Test

The easiest way to run integration tests is by providing network and operator information in a configuration file. This configuration file is passed into system properties.

$ ./gradlew integrationTest -PCONFIG_FILE="<ConfigurationFilePath>"

An example configuration file can be found in the repo here:

sdk/src/test/resources/client-config-with-operator.json

The format of the configuration file should be as follows:

{
    "network": {
        "<NodeAddress>": "<NodeAccountId>",
        ...
    },
    "operator": {
        "accountId": "<shard.realm.num>",
        "privateKey": "<PrivateKey>"
    }
}

If a configuration file is not provided, OPERATOR_ID and OPERATOR_KEY must be passed into system properties and integration tests will run against the Hedera test network.

$ ./gradlew integrationTest -POPERATOR_ID="<shard.realm.num>" -POPERATOR_KEY="<PrivateKey>"

HEDERA_NETWORK can optionally be used to use previewnet. This System Property can only be set to previewnet.

$ ./gradlew integrationTest -POPERATOR_ID="<shard.realm.num>" -POPERATOR_KEY="<PrivateKey>" -PHEDERA_NETWORK="previewnet"

Note: It is also possible to use a custom network in a configuration file and pass OPERATOR_ID and OPERATOR_KEY into system properties.

An example configuration file containing only network information can be found in the repo here:

sdk/src/test/resources/client-config.json

Examples

Requires OPERATOR_ID and OPERATOR_KEY to be in a .env file in the examples directory. Many examples run against the Hedera test network.

$ ./gradlew -q example:run<NameOfExample>
$ ./gradlew -q example:runGenerateKey

Contributing to this Project

We welcome participation from all developers! For instructions on how to contribute to this repo, please review the Contributing Guide.

License Information

Licensed under Apache License, Version 2.0 – see LICENSE in this repo or apache.org/licenses/LICENSE-2.0.