06-balance.adoc

Working with Account Balance

Polkaj provides Java-friendly wrappers to make some common operations. AccountRequests class provides common operations for address and balance.

Get total amount of issued coins

totalIssuance() method of AccountRequests class provides a functionality to request and process total amount of currently issues coins. For the query it encodes request to storage function TotalIssuance of the module Balances on the current Runtime.

final JavaHttpSubscriptionAdapter adapter = JavaHttpSubscriptionAdapter .newBuilder()
    .connectTo("wss://cc3-5.kusama.network")
    .build();
try (
    PolkadotApi client = PolkadotApi.newBuilder().subscriptionAdapter(adapter).build())
).build()) {
    System.out.println("Connected: " + adapter.connect().get());
    DotAmount total = AccountRequests.totalIssuance()
        // execute on RPC
        .execute(client)
        // get the value synchroniously
        .get();

    System.out.println(
            "Total Issued: " + DotAmountFormatter.autoFormatter().format(total)
    );
}

Get balance

balanceOf(address) method of AccountRequests class provides a functionality to request and process account info for the specified address. For the query it encodes request to storage function System of the module Account on the current Runtime.

try (
    PolkadotApi client =PolkadotApi.newBuilder().rpcCallAdapter(
        JavaHttpAdapter.newBuilder()
        .connectTo("wss://cc3-5.kusama.network")
        .build()
) {
    // request balance of Alice
    Address alice = Address.from("5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY");

    // execute on RPC
    AccountInfo accountInfo = AccountRequests.balanceOf(alice)
        .execute(client)
        .get();

    System.out.println(
            "Current balance: " +
            DotAmountFormatter.autoFormatter().format(accountInfo.getData().getFree())
    );
    System.out.println(
            "Current nonce  : " +
            accountInfo.getNonce()
    );
}

Transfer balance

AccountRequests.transfer() provides a builder to prepare the extrinsic. Use it to set values, such as from, to, and amount to transfer.

To make a valid extrinsic, it also needs the current Runtime Metadata and Extrinsic Context with Key Pari to make a signature.

Example

try (
    PolkadotApi client =PolkadotApi.newBuilder().rpcCallAdapter(
        JavaHttpAdapter.newBuilder()
        .connectTo("wss://cc3-5.kusama.network")
        .build()
) {
    // Build a context for the execution
    ExtrinsicContext context = ExtrinsicContext.newAutoBuilder(alice, client)
            .get()
            .build();

    // Current runtime meta
    Metadata metadata = client.execute(
                StandardCommands.getInstance().stateMetadata()
            )
            .thenApply(ScaleExtract.fromBytesData(new MetadataReader()))
            .get();

    // And build an actual call to the runtime method
    AccountRequests.Transfer transfer = AccountRequests.transfer()
            // get standard details from metadata (module and method id, etc)
            .runtime(metadata)
            // sender
            .from(alice)
            // recipient
            .to(bob)
            // amount to transfer
            .amount(amount)
            // sign with the context
            .sign(aliceKey, context)
            .build();

    // Finally, submit to the blockchain
     Hash256 txid = client.execute(
                    StandardCommands.getInstance()
                        .authorSubmitExtrinsic(transfer.encodeRequest())
            ).get();
}