HttpURLConnection

import java.net.HttpURLConnection;
import java.net.URL;
import java.io.OutputStream;

public class GraphQLQueryNative {

    private static final String ENDPOINT_URL = "https://streaming.bitquery.io/graphql";
    private static final String API_KEY = "*****"   //API KEY

    public static void main(String[] args) {
        try {
            String responseBody = executeQuery();
            System.out.println(responseBody);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static String executeQuery() throws Exception {
        URL url = new URL(ENDPOINT_URL);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setRequestProperty("X-API-KEY", API_KEY);
        conn.setDoOutput(true);

        String query = "subscription NotAlwaysWorkingSub {" +
    "EVM(network: eth, trigger_on: head) {" +
        "buyside: DEXTrades(" +
            "orderBy: {descending: Block_Time}," +
            "where: {" +
                "Trade: {" +
                    "Sell: {" +
                        "Currency: {" +
                            "SmartContract: {is: \\\"0x423f4e6138E475D85CF7Ea071AC92097Ed631eea\\\"}" +
                        "}" +
                    "}," +
                    "Dex: {" +
                        "ProtocolName: {is: \\\"uniswap_v3\\\"}," +
                        "Pair: {SmartContract: {}}" +
                    "}" +
                "}" +
            "}" +
        ") {" +
            "Block {" +
                "Number," +
                "Time" +
            "}," +
            "Transaction {" +
                "From," +
                "To," +
                "Hash" +
            "}," +
            "Trade {" +
                "Buy {" +
                    "Amount," +
                    "Buyer," +
                    "Currency {" +
                        "Name," +
                        "Symbol," +
                        "SmartContract" +
                    "}," +
                    "Seller," +
                    "Price" +
                "}," +
                "Sell {" +
                    "Amount," +
                    "Buyer," +
                    "Currency {" +
                        "Name," +
                        "SmartContract," +
                        "Symbol" +
                    "}," +
                    "Seller," +
                    "Price" +
                "}," +
                "Dex {" +
                    "ProtocolFamily," +
                    "ProtocolName," +
                    "SmartContract," +
                    "Pair {" +
                        "SmartContract" +
                    "}" +
                "}" +
            "}" +
        "}" +
    "}" +
"}";

        String payload = "{\"query\":\"" + query + "\",\"variables\":\"{}\"}";

        try (OutputStream os = conn.getOutputStream()) {
            byte[] input = payload.getBytes("utf-8");
            os.write(input, 0, input.length);
        }

        int responseCode = conn.getResponseCode();
        if (responseCode != HttpURLConnection.HTTP_OK) {
            throw new RuntimeException("Failed : HTTP error code : " + responseCode);
        }

        java.io.InputStream is = conn.getInputStream();
        java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
        String responseBody = s.hasNext() ? s.next() : "";

        conn.disconnect();

        return responseBody;
    }
}