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Watch ETH Events on Java SDK

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zhouqiang edited this page Jan 11, 2023 · 16 revisions

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>0.0.18</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 {
                final Deposits.LogDepositEventResponse event = it.component1();
                final EthBlock ethBlock = it.component2();
                // once received the event, print it
                String asJson = om.writeValueAsString(event);
                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 start from the 16 blocks ahead of the latest block
  • emit events with at least 16 block confirmations

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
}

The definition of log field is ethernum log definition

Reference

watchDeposit

watchDeposit is the method for watching LogDeposit events. watchDeposit is a non-blocking method, it runs in background, and returns Disposable for cancellation.

There are 3 overload for watchDeposit:

  • Disposable watchDeposit(Consumer<Tuple2<Deposits.LogDepositEventResponse, EthBlock>> consumer);
  • Disposable watchDeposit(Consumer<Tuple2<Deposits.LogDepositEventResponse, EthBlock>> consumer, BigInteger startBlockNumber);
  • Disposable watchDeposit(Consumer<Tuple2<Deposits.LogDepositEventResponse, EthBlock>> consumer, BigInteger startBlockNumber, Long requiredBlockConfirmation);

Parameter consumer should resolve the event, implement your own logic here.

The first overload is the default behavior, it watches events from the 16 blocks ahead of the latest block, and emit events with at least 16 block confirmations. The rest two overloads are for customizing the behavior.

Deposits.LogDepositEventResponse is the class for the event, it contains all the information of the event:

watchNftDeposit

watchNftDeposit is the method for watching LogNftDeposit events. watchNftDeposit is a non-blocking method, it runs in background, and returns Disposable for cancellation.

There are 3 overload for watchNftDeposit:

  • Disposable watchNftDeposit(Consumer<Tuple2<Deposits.LogNftDepositEventResponse, EthBlock>> consumer);
  • Disposable watchNftDeposit(Consumer<Tuple2<Deposits.LogNftDepositEventResponse, EthBlock>> consumer, BigInteger startBlockNumber);
  • Disposable watchNftDeposit(Consumer<Tuple2<Deposits.LogNftDepositEventResponse, EthBlock>> consumer, BigInteger startBlockNumber, Long requiredBlockConfirmation);

Parameter consumer should resolve the event, implement your own logic here.

The first overload is the default behavior, it watches events from the 16 blocks ahead of the latest block, and emit events with at least 16 block confirmations. The rest two overloads are for customizing the behavior.

Deposits.LogNftDepositEventResponse is the class for the event, it contains all the information of the event:

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