Java SDK: Your First Transaction
This section is a quick start guide for interacting with Algorand network using Java. This guide will help to install Algorand sandbox, which provides a node for testing and development. This guide will also help to install the Java SDK, create an account and submit your first transaction.
Install Sandbox¶
Info
This step is only required if you are not using AlgoKit. If you are using AlgoKit, you can spin up a sandbox using the LocalNet, see AlgoKit getting started guide for more information.
Prerequisites
- Docker Compose (install guide)
- Git (install guide)
Algorand provides a docker instance for setting up a node, which can be used to get started developing. To install and use this instance, follow these instructions.
git clone https://github.com/algorand/sandbox.git
cd sandbox
./sandbox up dev
This will install and start private network. To read more about Algorand networks see Algorand Networks.
More Information about the sandbox and how to use it.
Install Java SDK¶
Algorand provides an SDK for Java. The instructions for installing the SDK are as follows. The Java SDK is available in the MVN repository and can be used in your Maven project by including the following dependency.
Prerequisites
Java SDK requires Java 7+ and Android minSdkVersion 16+. Check for the latest version of the Java SDK here.
<dependency>
<groupId>com.algorand</groupId>
<artifactId>algosdk</artifactId>
<version>2.0.0</version>
</dependency>
The GitHub repository contains additional documentation and examples.
See the Java SDK reference documentation for more information on packages and methods.
The SDK is installed and can now interact with the Sandbox created earlier.
Create an Account¶
In order to interact with the Algorand blockchain, you must have a funded account. To quickly create a test account use the following code.
Account acct = new Account();
System.out.println("Address: " + acct.getAddress());
System.out.println("Passphrase: " + acct.toMnemonic());
Warning
Never share Mnemonic private keys. Production environments require stringent private key management. For more information on key management in community Wallets, click here. For the Algorand open source wallet, click here.
Fund the Account¶
Before sending transactions to the Algorand network, the account must be funded to cover the minimal transaction fees that exist on Algorand. In this example, we'll be using prefunded accounts available in the Sandbox. To fund an account on Testnet account use the Algorand faucet.
Info
All Algorand accounts require a minimum balance to be registered in the ledger. To read more about Algorand minimums see this link.
Connect Your Client¶
An Algod client must be instantiated prior to making calls to the API endpoints. You must provide values for <algod-address> and <algod-token>. The CLI tools implement the client natively. By default, the algodToken for each sandbox is set to its aaa... value and the algodAddress corresponds to http://localhost:4001.
String algodHost = "http://localhost";
int algodPort = 4001;
String algodToken = "a".repeat(64);
AlgodClient algodClient = new AlgodClient(algodHost, algodPort, algodToken);
// OR if the API provider requires a specific header key for the token
String tokenHeader = "X-API-Key";
AlgodClient otherAlgodClient = new AlgodClient(algodHost, algodPort, algodToken, tokenHeader);
Info
The example code connects to the sandbox Algod client. If you want to connect to a public API client, change the host, port, and token parameters to match the API service. See some service available here
Info
If you are connecting to the Testnet, a dispenser is available here
Check Your Balance¶
Before moving on to the next step, make sure your account has been funded by the faucet.
Response<com.algorand.algosdk.v2.client.model.Account> acctInfoResp = algodClient
.AccountInformation(acct.getAddress()).execute();
com.algorand.algosdk.v2.client.model.Account acctInfo = acctInfoResp.body();
// print one of the fields in the account info response
System.out.printf("Current balance: %d", acctInfo.amount);
Build First Transaction¶
Transactions are used to interact with the Algorand network. To create a payment transaction use the following code.
Response<TransactionParametersResponse> suggestedParams = algodClient.TransactionParams().execute();
Integer amount = 1000000; // 1 Algo
Transaction ptxn = Transaction.PaymentTransactionBuilder()
.sender(acct.getAddress())
.amount(amount)
.receiver(acct2.getAddress())
.suggestedParams(suggestedParams.body()).build();
Info
Algorand supports many transaction types. To see what types are supported see Transactions.
Sign First Transaction¶
Before the transaction is considered valid, it must be signed by a private key. Use the following code to sign the transaction.
SignedTransaction sptxn = acct.signTransaction(ptxn);
Info
Algorand provides additional ways for transactions to be signed, other than by a standalone account. For more information see Authorization.
Submit the Transaction¶
The signed transaction can now be submitted to the network. The SDK waitForConfirmation utility function is called after the transaction is submitted to wait until the transaction is broadcast to the Algorand blockchain and is confirmed.
// encode the transaction
byte[] encodedTxBytes = Encoder.encodeToMsgPack(sptxn);
// submit the transaction to the algod server
Response<PostTransactionsResponse> resp = algodClient.RawTransaction().rawtxn(encodedTxBytes).execute();
// wait for the transaction to be confirmed
String txid = resp.body().txId;
PendingTransactionResponse result = Utils.waitForConfirmation(algodClient, txid, 4);
System.out.printf("Transaction %s confirmed in round %d\n", txid, result.confirmedRound);
Viewing the Transaction¶
To view the transaction we submitted to the sandbox Algod, open Lora and choose LocalNet configuration option, then search for the transaction ID.
To view a transaction submitted to public network like testnet, open Lora or Pera Explorer and paste the transaction ID into the search bar.