CaverExample_klay_sign.java

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.klaytn.caver.Caver;
import com.klaytn.caver.methods.response.Bytes;
import com.klaytn.caver.wallet.keyring.SingleKeyring;
import io.github.cdimascio.dotenv.Dotenv;
import okhttp3.Credentials;
import org.web3j.protocol.http.HttpService;

import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * Hello world for caver-java Klaytn SDK! Please read the README before starting :)
 * Related article - Korean: https://ko.docs.klaytn.com/bapp/sdk/caver-java/getting-started
 * Related reference - English: https://docs.klaytn.com/bapp/sdk/caver-java/getting-started
 */
public class CaverExample {
    public static void main(String[] args) {
        try {
            loadEnv();
            run();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static String objectToString(Object value) throws JsonProcessingException {
        ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
        return ow.writeValueAsString(value);
    }

    public static void run() throws Exception {
        // In the caver, almost everything starts with the caver. Let's create a caver instance
        Caver caver = new Caver("http://localhost:8551");

        // Now that we have created the caver instance, we can do whatever we want with the caver.
        // Write your own code below using Caver instance :)
        SingleKeyring singleKeyring = caver.wallet.keyring.createFromPrivateKey("0x{privateKey}");
        System.out.println(objectToString(singleKeyring));

        Bytes signed = caver.rpc.klay.sign(singleKeyring.getAddress(), "0xabcd").send();
        objectToString(signed);
    }
}