Any operation contracting with the TRON network is a transaction. A transaction can be TRX transfer, stake & unstake, Trigger Smart Contract, Etc.

Only resource consumption transactions are available to acquire on the chain.

The Routine for Sending

A normal routine for sending a transaction is:

Create -> Sign -> Broadcast -> (wait) -> Lookup and get receipt

Create a Transaction

Each non-inquiry function creates an unsigned transaction, for example:

public TransactionExtention transfer(String fromAddress, String toAddress, long amount) throws IllegalException {

        ByteString rawFrom = parseAddress(fromAddress);
        ByteString rawTo = parseAddress(toAddress);

        TransferContract req = TransferContract.newBuilder()
                .setOwnerAddress(rawFrom)
                .setToAddress(rawTo)
                .setAmount(amount)
                .build();
        TransactionExtention txnExt = blockingStub.createTransaction2(req);

        if(SUCCESS != txnExt.getResult().getCode()){
            throw new IllegalException(txnExt.getResult().getMessage().toStringUtf8());
        }

        return txnExt;
    }

Add Extra Parameters

core.TransactionBuilder allows you to add or modify parameters before signing, for example:

TransactionBuilder builder = new TransactionBuilder(transaction);
builder.setFeeLimit(100000000L);
builder.setMemo("memo");
//call TransactionBuilder.build() to get a new transaction
builder.build();

Note that only smart contract transactions require a fee limit.

Signing

There are two ways to sign a transaction:

Sign with the binding private key

Every ApiWrapper instance is initiated with a private key(or a hexadecimal string of 64 characters in length). Simply sign a transaction like this:

Transction signedTransaction = wrapper.signTransaction(transaction);

Sign with a specific private key

Regardless of the binding private key, you can use any private key to sign the transaction, like below:

Transaction signedTransaction = wrapper.signTransaction(transaction, SECP256K1.KeyPair);

Refer to org.tron.trident.crypto.SECP256K1 for construct an SECP256K1.KeyPair.

Broadcast

Transaction hash may change due to any modification to the original transaction (except the signature).
Transaction hash is re-calculated inside the function of ApiWrapper.broadcastTransaction(Transaction txn) before transaction is broadcasted.

wrapper.broadcastTransaction(signedTransaction);

//return transaction hash if successfully broadcasted, otherwise the error code