Java SCORE Examples

This repository contains SCORE (Smart Contract for ICON) examples written in Java.

Requirements

You need to install JDK 11 or later version. Visit OpenJDK.net for prebuilt binaries. Or you can install a proper OpenJDK package from your OS vendors.

In macOS:

$ brew tap AdoptOpenJDK/openjdk
$ brew cask install adoptopenjdk11

In Linux (Ubuntu 20.04):

$ sudo apt install openjdk-11-jdk

How to Run

1. Build the project

$ ./gradlew build

The compiled jar bundle will be generated at ./hello-world/build/libs/hello-world-0.1.0.jar.

2. Optimize the jar

You need to optimize your jar bundle before you deploy it to local or ICON networks. This involves some pre-processing to ensure the actual deployment successful.

gradle-javaee-plugin is a Gradle plugin to automate the process of generating the optimized jar bundle. Run the optimizedJar task to generate the optimized jar bundle.

$ ./gradlew optimizedJar

The output jar will be located at ./hello-world/build/libs/hello-world-0.1.0-optimized.jar.

3. Deploy the optimized jar

Using goloop CLI command

Now you can deploy the optimized jar to ICON networks that support the Java SCORE execution environment. Assuming you are running a local network that is listening on port 9082 for incoming requests, you can create a deploy transaction with the optimized jar and deploy it to the local network as follows.

$ goloop rpc sendtx deploy ./hello-world/build/libs/hello-world-0.1.0-optimized.jar \
    --uri http://localhost:9082/api/v3 \
    --key_store <your_wallet_json> --key_password <password> \
    --nid 3 --step_limit=1000000 \
    --content_type application/java \
    --param name=Alice

[Note] The content type should be application/java instead of application/zip to differentiate it with the Python SCORE deployment.

Using deployJar extension

Starting with version 0.7.2 of gradle-javaee-plugin, you can also use the deployJar extension to specify all the information required for deployment.

deployJar {
    endpoints {
        local {
            uri = 'http://localhost:9082/api/v3'
            nid = 3
        }
    }
    keystore = rootProject.hasProperty('keystoreName') ? "$keystoreName" : ''
    password = rootProject.hasProperty('keystorePass') ? "$keystorePass" : ''
    parameters {
        arg('name', 'Alice')
    }
}

Now you can run deployToLocal task as follows.

$ ./gradlew hello-world:deployToLocal -PkeystoreName=<your_wallet_json> -PkeystorePass=<password>

> Task :hello-world:deployToLocal
>>> deploy to http://localhost:9082/api/v3
>>> optimizedJar = ./hello-world/build/libs/hello-world-0.1.0-optimized.jar
>>> keystore = <your_wallet_json>
Succeeded to deploy: 0x699534c9f5277539e1b572420819141c7cf3e52a6904a34b2a2cdb05b95ab0a3
SCORE address: cxd6d044b01db068cded47bde12ed4f15a6da9f1d8

[Note] If you want to deploy to Lisbon testnet, use the following configuration for the endpoint and run deployToLisbon task.

deployJar {
    endpoints {
        lisbon {
            uri = 'https://lisbon.net.solidwallet.io/api/v3'
            nid = 0x2
        }
        ...
    }
}

4. Verify the execution

Check the deployed SCORE address first using the txresult command.

$ goloop rpc txresult <tx_hash> --uri http://localhost:9082/api/v3
{
  ...
  "scoreAddress": "cxaa736426a9caed44c59520e94da2d64888d9241b",
  ...
}

Then you can invoke getGreeting method via the following call command.

$ goloop rpc call --to <score_address> --method getGreeting --uri http://localhost:9082/api/v3
"Hello Alice!"

Testing

Two testing frameworks are provided as to be used for different purposes: one is for unit testing and the other is for integration testing.

Unit testing

testsvc subproject can be used for the unit testing, and it provides a SCORE execution emulation layer can be integrated with the JUnit 5 and Mockito frameworks. Now javaee-unittest artifact is used to perform the unit testing.

Here are the sample unit test cases.

• HelloWorld
• MultisigWallet
• Crowdsale
• IRC3Token (NFT)
• IRC2BurnableToken
• SampleToken

Integration testing

testinteg subproject can be used for the integration testing. It assumes there is a running ICON network (either local or remote) that can be connected for the testing. It uses the ICON SDK for Java to interact with the network. The default configuration is for gochain-local network. If you want to change this configuration, either modify the configuration file directly or set the proper system property (env.props) when you run the integration testing (see example).

Here are the sample integration test cases.

• MultisigWallet
• Crowdsale
• IRC3Token (NFT)

Use integrationTest task to run the integration testing. Here is the example of invoking the MultisigWallet integration testing.

$ ./gradlew multisig-wallet:integrationTest

Java SCORE Structure

Comparison to Python SCORE

Name	Python SCORE	Java SCORE
External decorator	@external	@External
- (readonly)	@external(readonly=True)	@External(readonly=true)
Payable decorator	@payable	@Payable
Eventlog decorator	@eventlog	@EventLog
- (indexed)	@eventlog(indexed=1)	@EventLog(indexed=1)
fallback signature	def fallback	void fallback()
SCORE initialize	override on_install method	define a public constructor
Default parameters	native language support	@Optional

[NOTE] All external Java methods must have a public modifier, and should be instance methods.

How to invoke a external method of another SCORE

One SCORE can invoke an external method of another SCORE using the following APIs.

// [package score.Context]
public static Object call(Address targetAddress, String method, Object... params);

public static Object call(BigInteger value,
                          Address targetAddress, String method, Object... params);

The following example is for calling tokenFallback.

if (_to.isContract()) {
    Context.call(_to, "tokenFallback", _from, _value, dataBytes);
}

References

• Java SCORE Overview
• SCORE API document
• Gradle plugin for JavaEE
• A Java SCORE Library for Standard Tokens
• scorex package for Java SCORE
• An Unit Testing Framework for Java SCORE
• A fast and small JSON parser and writer for Java
• goloop CLI command reference

License

This project is available under the Apache License, Version 2.0.