Telnyx Voice Gather Java

team-telnyx/telnyx-voice-gather-java

>- Collect DTMF input and speech from callers using standard gather or AI-powered gather. Build interactive voice menus and AI voice assistants. This skill provides Java SDK examples.

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Install

one command, takes just this skill from the repository

npx skills add https://github.com/team-telnyx/ai --skill telnyx-voice-gather-java

The instruction itself

15 sections, as written by the author

Telnyx Voice Gather - Java

Installation

<!-- Maven -->
<dependency>
    <groupId>com.telnyx.sdk</groupId>
    <artifactId>telnyx</artifactId>
    <version>6.36.0</version>
</dependency>

// Gradle
implementation("com.telnyx.sdk:telnyx:6.36.0")

Setup

import com.telnyx.sdk.client.TelnyxClient;
import com.telnyx.sdk.client.okhttp.TelnyxOkHttpClient;

TelnyxClient client = TelnyxOkHttpClient.fromEnv();

All examples below assume client is already initialized as shown above.

Error Handling

All API calls can fail with network errors, rate limits (429), validation errors (422),

or authentication errors (401). Always handle errors in production code:

import com.telnyx.sdk.errors.TelnyxServiceException;

try {
    var result = client.messages().send(params);
} catch (TelnyxServiceException e) {
    System.err.println("API error " + e.statusCode() + ": " + e.getMessage());
    if (e.statusCode() == 422) {
        System.err.println("Validation error — check required fields and formats");
    } else if (e.statusCode() == 429) {
        // Rate limited — wait and retry with exponential backoff
        Thread.sleep(1000);
    }
}

Common error codes: 401 invalid API key, 403 insufficient permissions,

404 resource not found, 422 validation error (check field formats),

429 rate limited (retry with exponential backoff).

Add messages to AI Assistant

Add messages to the conversation started by an AI assistant on the call.

POST /calls/{call_control_id}/actions/ai_assistant_add_messages

Optional: client_state (string), command_id (string), messages (array[object])

import com.telnyx.sdk.models.calls.actions.ActionAddAiAssistantMessagesParams;
import com.telnyx.sdk.models.calls.actions.ActionAddAiAssistantMessagesResponse;

ActionAddAiAssistantMessagesResponse response = client.calls().actions().addAiAssistantMessages("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: result (string)

Start AI Assistant

Start an AI assistant on the call. Expected Webhooks:

call.conversation.ended
call.conversation_insights.generated

POST /calls/{call_control_id}/actions/ai_assistant_start

Optional: assistant (object), client_state (string), command_id (string), greeting (string), interruption_settings (object), message_history (array[object]), participants (array[object]), send_message_history_updates (boolean), transcription (object), voice (string), voice_settings (object)

import com.telnyx.sdk.models.calls.actions.ActionStartAiAssistantParams;
import com.telnyx.sdk.models.calls.actions.ActionStartAiAssistantResponse;

ActionStartAiAssistantResponse response = client.calls().actions().startAiAssistant("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: conversation_id (uuid), result (string)

Stop AI Assistant

Stop an AI assistant on the call.

POST /calls/{call_control_id}/actions/ai_assistant_stop

Optional: client_state (string), command_id (string)

import com.telnyx.sdk.models.calls.actions.ActionStopAiAssistantParams;
import com.telnyx.sdk.models.calls.actions.ActionStopAiAssistantResponse;

ActionStopAiAssistantResponse response = client.calls().actions().stopAiAssistant("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: result (string)

Gather

Gather DTMF signals to build interactive menus. You can pass a list of valid digits. The Answer command must be issued before the gather command.

POST /calls/{call_control_id}/actions/gather

Optional: client_state (string), command_id (string), gather_id (string), initial_timeout_millis (int32), inter_digit_timeout_millis (int32), maximum_digits (int32), minimum_digits (int32), terminating_digit (string), timeout_millis (int32), valid_digits (string)

import com.telnyx.sdk.models.calls.actions.ActionGatherParams;
import com.telnyx.sdk.models.calls.actions.ActionGatherResponse;

ActionGatherResponse response = client.calls().actions().gather("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: result (string)

Gather stop

Stop current gather. Expected Webhooks:

call.gather.ended

POST /calls/{call_control_id}/actions/gather_stop

Optional: client_state (string), command_id (string)

import com.telnyx.sdk.models.calls.actions.ActionStopGatherParams;
import com.telnyx.sdk.models.calls.actions.ActionStopGatherResponse;

ActionStopGatherResponse response = client.calls().actions().stopGather("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: result (string)

Gather using AI

Gather parameters defined in the request payload using a voice assistant. You can pass parameters described as a JSON Schema object and the voice assistant will attempt to gather these informations.

POST /calls/{call_control_id}/actions/gather_using_ai — Required: parameters

Optional: assistant (object), client_state (string), command_id (string), gather_ended_speech (string), greeting (string), interruption_settings (object), language (object), message_history (array[object]), send_message_history_updates (boolean), send_partial_results (boolean), transcription (object), user_response_timeout_ms (integer), voice (string), voice_settings (object)

import com.telnyx.sdk.core.JsonValue;
import com.telnyx.sdk.models.calls.actions.ActionGatherUsingAiParams;
import com.telnyx.sdk.models.calls.actions.ActionGatherUsingAiResponse;

ActionGatherUsingAiParams params = ActionGatherUsingAiParams.builder()
    .callControlId("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ")
    .parameters(ActionGatherUsingAiParams.Parameters.builder()
        .putAdditionalProperty("properties", JsonValue.from("bar"))
        .putAdditionalProperty("required", JsonValue.from("bar"))
        .putAdditionalProperty("type", JsonValue.from("bar"))
        .build())
    .build();
ActionGatherUsingAiResponse response = client.calls().actions().gatherUsingAi(params);

Returns: conversation_id (uuid), result (string)

Gather using audio

Play an audio file on the call until the required DTMF signals are gathered to build interactive menus. You can pass a list of valid digits along with an 'invalid_audio_url', which will be played back at the beginning of each prompt. Playback will be interrupted when a DTMF signal is received.

POST /calls/{call_control_id}/actions/gather_using_audio

Optional: audio_url (string), client_state (string), command_id (string), inter_digit_timeout_millis (int32), invalid_audio_url (string), invalid_media_name (string), maximum_digits (int32), maximum_tries (int32), media_name (string), minimum_digits (int32), terminating_digit (string), timeout_millis (int32), valid_digits (string)

import com.telnyx.sdk.models.calls.actions.ActionGatherUsingAudioParams;
import com.telnyx.sdk.models.calls.actions.ActionGatherUsingAudioResponse;

ActionGatherUsingAudioResponse response = client.calls().actions().gatherUsingAudio("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ");

Returns: result (string)

Gather using speak

Convert text to speech and play it on the call until the required DTMF signals are gathered to build interactive menus. You can pass a list of valid digits along with an 'invalid_payload', which will be played back at the beginning of each prompt. Speech will be interrupted when a DTMF signal is received.

POST /calls/{call_control_id}/actions/gather_using_speak — Required: voice, payload

Optional: client_state (string), command_id (string), inter_digit_timeout_millis (int32), invalid_payload (string), language (enum: arb, cmn-CN, cy-GB, da-DK, de-DE, en-AU, en-GB, en-GB-WLS, en-IN, en-US, es-ES, es-MX, es-US, fr-CA, fr-FR, hi-IN, is-IS, it-IT, ja-JP, ko-KR, nb-NO, nl-NL, pl-PL, pt-BR, pt-PT, ro-RO, ru-RU, sv-SE, tr-TR), maximum_digits (int32), maximum_tries (int32), minimum_digits (int32), payload_type (enum: text, ssml), service_level (enum: basic, premium), terminating_digit (string), timeout_millis (int32), valid_digits (string), voice_settings (object)

import com.telnyx.sdk.models.calls.actions.ActionGatherUsingSpeakParams;
import com.telnyx.sdk.models.calls.actions.ActionGatherUsingSpeakResponse;

ActionGatherUsingSpeakParams params = ActionGatherUsingSpeakParams.builder()
    .callControlId("v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ")
    .payload("say this on call")
    .voice("male")
    .build();
ActionGatherUsingSpeakResponse response = client.calls().actions().gatherUsingSpeak(params);

Returns: result (string)

Webhooks

Webhook Verification

Telnyx signs webhooks with Ed25519. Each request includes telnyx-signature-ed25519

and telnyx-timestamp headers. Always verify signatures in production:

import com.telnyx.sdk.core.UnwrapWebhookParams;
import com.telnyx.sdk.core.http.Headers;

// In your webhook handler (e.g., Spring — use raw body):
@PostMapping("/webhooks")
public ResponseEntity<String> handleWebhook(
    @RequestBody String payload,
    HttpServletRequest request) {
  try {
    Headers headers = Headers.builder()
        .put("telnyx-signature-ed25519", request.getHeader("telnyx-signature-ed25519"))
        .put("telnyx-timestamp", request.getHeader("telnyx-timestamp"))
        .build();
    var event = client.webhooks().unwrap(
        UnwrapWebhookParams.builder()
            .body(payload)
            .headers(headers)
            .build());
    // Signature valid — process the event
    System.out.println("Received webhook event");
    return ResponseEntity.ok("OK");
  } catch (Exception e) {
    System.err.println("Webhook verification failed: " + e.getMessage());
    return ResponseEntity.badRequest().body("Invalid signature");
  }
}

The following webhook events are sent to your configured webhook URL.

All webhooks include telnyx-timestamp and telnyx-signature-ed25519 headers for Ed25519 signature verification. Use client.webhooks.unwrap() to verify.

| Event | Description |

|-------|-------------|

| CallAIGatherEnded | Call AI Gather Ended |

| CallAIGatherMessageHistoryUpdated | Call AI Gather Message History Updated |

| CallAIGatherPartialResults | Call AI Gather Partial Results |

| callGatherEnded | Call Gather Ended |

Webhook payload fields

CallAIGatherEnded

| Field | Type | Description |

|-------|------|-------------|

| data.record_type | enum: event | Identifies the type of the resource. |

| data.event_type | enum: call.ai_gather.ended | The type of event being delivered. |

| data.id | uuid | Identifies the type of resource. |

| data.occurred_at | date-time | ISO 8601 datetime of when the event occurred. |

| data.payload.call_control_id | string | Call ID used to issue commands via Call Control API. |

| data.payload.connection_id | string | Telnyx connection ID used in the call. |

| data.payload.call_leg_id | string | ID that is unique to the call and can be used to correlate webhook events. |

| data.payload.call_session_id | string | ID that is unique to the call session and can be used to correlate webhook events. |

| data.payload.client_state | string | State received from a command. |

| data.payload.from | string | Number or SIP URI placing the call. |

| data.payload.to | string | Destination number or SIP URI of the call. |

| data.payload.message_history | array[object] | The history of the messages exchanged during the AI gather |

| data.payload.result | object | The result of the AI gather, its type depends of the parameters provided in the command |

| data.payload.status | enum: valid, invalid | Reflects how command ended. |

CallAIGatherMessageHistoryUpdated

| Field | Type | Description |

|-------|------|-------------|

| data.record_type | enum: event | Identifies the type of the resource. |

| data.event_type | enum: call.ai_gather.message_history_updated | The type of event being delivered. |