CKB SDK Java

Java SDK for Nervos CKB.

Prerequisites

• Java 8
• Gradle 5.0 or later

Installation

You can generate the jar and import manually.

git clone https://github.com/nervosnetwork/ckb-sdk-java.git

cd ckb-sdk-java

gradle shadowJar  // ./gradlew shadowJar 

A console-{version}-all.jar package will be generated in console/build/libs, which you can put into your project to develop with it.

If you don't want to generate the jar by yourself, you can download a build from releases.

Import Jar to Project

When you need to import ckb-java-sdk dependency to your project, you can add the console-{version}-all.jar to your project libs package.

If you use Java IDE (eg. IntelliJ IDEA or Eclipse or other Editors), you can import jar according to IDE option help documents.

Usage

JSON-RPC

You can make JSON-RPC request to your CKB node URL with this SDK. Below are some examples:

Api api = new Api("your-ckb-node-url");

// using RPC `get_tip_block_number`, it will return the latest block number
BigInteger blockNumber = api.getTipBlockNumber();

// using RPC `get_block_hash` with block number as parameter, it will return block hash
String blockNumber = "0"
String blockHash = api.getBlockHash(blockNumber);

// using RPC `get_block` with block hash as parameter, it will return block object
Block block = api.getBlock(blockHash);

You can see more JSON-RPC requests from RPC Document

Transfer

console/example/TransactionExample.java provides sendCapacity method with any amount inputs which belong to any amount private keys.

You can reference detail example in console/example/TransactionExample.java.

  Api api = new Api("your-ckb-node-url");

  List<CellInput> inputs = Arrays.asList(
    input1, // Input from address 'cktxxx', capacity 100 CKB
    input2, // Input from address 'cktxxx', capacity 200 CKB
    input3, // Input from address 'cktxxx', capacity 300 CKB
  );
  
  List<CellOutput> outputs = Arrays.asList(
    output1, // Output to address 'cktxxx', capacity 200
    output2, // Output to address 'cktxxx', capacity 300
    output3, // Output to address 'cktxxx' as change, capacity 100
  );
  
  TransactionBuilder builder = new TransactionBuilder(api);
  
  builder.addInputs(inputs);
  
  builder.addOutputs(outputs);
  
  builder.signInput(0, privateKey1);
  builder.signInput(1, privateKey2);
  builder.signInput(2, privateKey3);
  
  String hash = api.sendTransaction(builder.getTransaction());

Address

You can generate ckb address through this SDK as below:

There are many address generating methods, and this is just an example.

// Generate ckb testnet address
AddressUtils utils = new AddressUtils(Network.TESTNET);

// Generate public key from private key through SECP256K1
String publicKey =
    Sign.publicKeyFromPrivate(
            Numeric.toBigInt(
                "e79f3207ea4980b7fed79956d5934249ceac4751a4fae01a0f7c4a96884bc4e3"),
            true)
        .toString(16);

String address = utils.generateFromPublicKey(publicKey);

Development

We use Google Java Code Format and follow Google Checkstyle for development.

If verifyGoogleJavaFormat FAILED happens when you build this project, please format your code with Google Java Code Format or execute ./gradlew goJF on macOS and Linux, or gradlew goJF on Windows.

If you use IntelliJ IDEA to develop, you can install google-java-format plugin to format code automatically.

License

The SDK is available as open source under the terms of the MIT License.

Changelog

See CHANGELOG for more information.