Watch ETH Events on Java SDK

Introduction

When depositing and withdrawing assets between ETH and L2, it emits "events" when the transaction is completed. The event could be used as the signal for a transaction to be completed successfully.

Example

The following example assumes that you have Java and Maven installed.

The following example contains a demo application for watching events of depositing NTF from ETH to L2.

Step 1: Create a maven project and import dependency

Create new maven project by:

mvn archetype:generate -DgroupId=com.example.app -DartifactId=reddio-example-watch-events -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false -DarchetypeVersion=1.4

Then add the reddio-api dependency:

<dependency>
    <groupId>com.reddio</groupId>
    <artifactId>reddio-api</artifactId>
    <version>0.0.15</version>
</dependency>

Step 2: codes about watching all of Deposit events

There are example codes for watching Deposit events:

public class App 
{
    public static void main( String[] args )
    {
        DefaultReddioRestClient restClient = DefaultReddioRestClient.testnet();
        DefaultEthereumInteraction ethereumInteraction = DefaultEthereumInteraction.build(
                restClient,
                DefaultEthereumInteraction.GOERIL_ID,
                // replace with your eth node address
                "https://eth-goerli.g.alchemy.com/v2/<your-api-key>",
                // we do not need private key for this example
                "0x0"
        );
        // object mapper for JSON serialization
        ObjectMapper om = new ObjectMapper();
        // notice the method watchDeposit would not block the thread, it runs in background, and returns Disposable for cancellation
        Disposable disposable = ethereumInteraction.watchDeposit((it) -> {
            try {
                // once received the event, print it
                String asJson = om.writeValueAsString(it);
                System.out.println(asJson);
            } catch (JsonProcessingException e) {
                throw new RuntimeException(e);
            }
        });


        try {
            Thread.sleep(Duration.ofSeconds(600).toMillis());

        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        // stop watching
        disposable.dispose();
    }
}

Please notice that the default behavior of watchDeposit is:

• watching events from the latest block
• emit events with at least 16 block confirmation

To change the behavior, you could use other overloads of watchDeposit, and change the parameters: startBlockNumber and requiredBlockConfirmation.

Step 3: run the application and give it a try

You could run the application, then deposit some assets on https://demos.reddio.com. As the transaction completes, you could see the output like this on the console:

{"log":{"removed":false,"logIndex":72,"transactionIndex":23,"transactionHash":"0x93df32e6a5adc801580f00a9f0681986314059c63fd0134f522ae94859b59b38","blockHash":"0x85036bf550a8caca902ef3b43499e53cf2788fee36c2130e4041e6cc2ca01a44","blockNumber":8281301,"address":"0x8eb82154f314ec687957ce1e9c1a5dc3a3234df9","data":"0x00000000000000000000000076f2fc7ed90039d986e3eb4db294f05e160c8f0301c2847406b96310a32c379536374ec034b732633e8675860f20f4141e701ff4000000000000000000000000000000000000000000000000000000000165153c0352f9ffd821a525051de2d71126113505a7b0a73d98dbc0ac0ff343cfbdef5e00000000000000000000000000000000000000000000000000005af3107a40000000000000000000000000000000000000000000000000000000000000000064","type":null,"topics":["0x06724742ccc8c330a39a641ef02a0b419bd09248360680bb38159b0a8c2635d6"],"logIndexRaw":"0x48","transactionIndexRaw":"0x17","blockNumberRaw":"0x7e5cd5"},"depositorEthKey":"0x76f2fc7ed90039d986e3eb4db294f05e160c8f03","starkKey":795995337730000219295083279675166181323994377230540967472507439971862323188,"vaultId":23401788,"assetType":1503545437449673444103803151627333814355897720185181380161647770114038034270,"nonQuantizedAmount":100000000000000,"quantizedAmount":100}