Java Beispiel

        <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.8</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.9.8</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.8</version>
</dependency>
    

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;

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

public class Main {

    public static void main(String[] args) throws JsonProcessingException {

        ObjectMapper mapper = new ObjectMapper();
        mapper.getFactory().configure(JsonGenerator.Feature.ESCAPE_NON_ASCII, true);

        ObjectNode messages = mapper.createObjectNode();
        messages.put("text", "Message via API");
        messages.put("type", "alert");
        messages.put("sender", "");

        ObjectNode recipients = mapper.createObjectNode();
        recipients.put("value", "33612345678");

        ObjectNode sms = mapper.createObjectNode();
        ObjectNode data = mapper.createObjectNode();
        ArrayNode numero = mapper.createArrayNode();

        ObjectNode gsm = mapper.createObjectNode();

        numero.add(recipients);
        gsm.set("gsm",numero);

        sms.set("message",messages);
        sms.set("recipients",gsm);

        data.putPOJO("sms",sms);

        String payload = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(data);

        try {
            Main hce = new Main();
            String response = hce.post("https://api.smsfactor.com/send", payload);
            System.out.println(response);
        } catch(IOException ioe) {
            ioe.printStackTrace();
        }

    }
    public String post(String postUrl, String data) throws IOException {
        URL url = new URL(postUrl);
        String token = "your.token";//Your first token must be generated on our plateform at https://my.smsfactor.com/developers/api-tokens
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("POST");
        con.setRequestProperty("Accept", "application/json");
        con.setRequestProperty("Authorization","Bearer " + token);
        con.setDoOutput(true);

        this.sendData(con, data);

        return this.read(con.getInputStream());
    }

    protected void sendData(HttpURLConnection con, String data) throws IOException {
        DataOutputStream wr = null;
        try {
            wr = new DataOutputStream(con.getOutputStream());
            wr.writeBytes(data);
            wr.flush();
            wr.close();
        } catch(IOException exception) {
            throw exception;
        } finally {
            this.closeQuietly(wr);
        }
    }

    private String read(InputStream is) throws IOException {
        BufferedReader in = null;
        String inputLine;
        StringBuilder body;
        try {
            in = new BufferedReader(new InputStreamReader(is));

            body = new StringBuilder();

            while ((inputLine = in.readLine()) != null) {
                body.append(inputLine);
            }
            in.close();

            return body.toString();
        } catch(IOException ioe) {
            throw ioe;
        } finally {
            this.closeQuietly(in);
        }
    }

    protected void closeQuietly(Closeable closeable) {
        try {
            if( closeable != null ) {
                closeable.close();
            }
        } catch(IOException ex) {

        }
    }
}