Telnyx Fax - Java

Installation

<!-- Maven -->
<dependency>
    <groupId>com.telnyx.sdk</groupId>
    <artifactId>telnyx-java</artifactId>
    <version>6.26.0</version>
</dependency>

// Gradle
implementation("com.telnyx.sdk:telnyx-java:6.26.0")

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).

Important Notes

Phone numbers must be in E.164 format (e.g., +13125550001). Include the + prefix and country code. No spaces, dashes, or parentheses.
Pagination: List methods return a page. Use .autoPager() for automatic iteration: for (var item : page.autoPager()) { ... }. For manual control, use .hasNextPage() and .nextPage().

List all Fax Applications

This endpoint returns a list of your Fax Applications inside the 'data' attribute of the response. You can adjust which applications are listed by using filters. Fax Applications are used to configure how you send and receive faxes using the Programmable Fax API with Telnyx.

GET /fax_applications

import com.telnyx.sdk.models.faxapplications.FaxApplicationListPage;
import com.telnyx.sdk.models.faxapplications.FaxApplicationListParams;

FaxApplicationListPage page = client.faxApplications().list();

Returns: active (boolean), anchorsite_override (enum: Latency, Chicago, IL, Ashburn, VA, San Jose, CA, Sydney, Australia, Amsterdam, Netherlands, London, UK, Toronto, Canada, Vancouver, Canada, Frankfurt, Germany), application_name (string), created_at (string), id (string), inbound (object), outbound (object), record_type (string), tags (array[string]), updated_at (string), webhook_event_failover_url (uri), webhook_event_url (uri), webhook_timeout_secs (integer | null)

Creates a Fax Application

Creates a new Fax Application based on the parameters sent in the request. The application name and webhook URL are required. Once created, you can assign phone numbers to your application using the /phone_numbers endpoint.

POST /fax_applications — Required: application_name, webhook_event_url

Optional: active (boolean), anchorsite_override (enum: Latency, Chicago, IL, Ashburn, VA, San Jose, CA, Sydney, Australia, Amsterdam, Netherlands, London, UK, Toronto, Canada, Vancouver, Canada, Frankfurt, Germany), inbound (object), outbound (object), tags (array[string]), webhook_event_failover_url (uri), webhook_timeout_secs (integer | null)

import com.telnyx.sdk.models.faxapplications.FaxApplicationCreateParams;
import com.telnyx.sdk.models.faxapplications.FaxApplicationCreateResponse;

FaxApplicationCreateParams params = FaxApplicationCreateParams.builder()
    .applicationName("fax-router")
    .webhookEventUrl("https://example.com")
    .build();
FaxApplicationCreateResponse faxApplication = client.faxApplications().create(params);

Retrieve a Fax Application

Return the details of an existing Fax Application inside the 'data' attribute of the response.

GET /fax_applications/{id}

import com.telnyx.sdk.models.faxapplications.FaxApplicationRetrieveParams;
import com.telnyx.sdk.models.faxapplications.FaxApplicationRetrieveResponse;

FaxApplicationRetrieveResponse faxApplication = client.faxApplications().retrieve("1293384261075731499");

Update a Fax Application

Updates settings of an existing Fax Application based on the parameters of the request.

PATCH /fax_applications/{id} — Required: application_name, webhook_event_url

Optional: active (boolean), anchorsite_override (enum: Latency, Chicago, IL, Ashburn, VA, San Jose, CA, Sydney, Australia, Amsterdam, Netherlands, London, UK, Toronto, Canada, Vancouver, Canada, Frankfurt, Germany), fax_email_recipient (string | null), inbound (object), outbound (object), tags (array[string]), webhook_event_failover_url (uri), webhook_timeout_secs (integer | null)

import com.telnyx.sdk.models.faxapplications.FaxApplicationUpdateParams;
import com.telnyx.sdk.models.faxapplications.FaxApplicationUpdateResponse;

FaxApplicationUpdateParams params = FaxApplicationUpdateParams.builder()
    .id("1293384261075731499")
    .applicationName("fax-router")
    .webhookEventUrl("https://example.com")
    .build();
FaxApplicationUpdateResponse faxApplication = client.faxApplications().update(params);

Deletes a Fax Application

Permanently deletes a Fax Application. Deletion may be prevented if the application is in use by phone numbers.

DELETE /fax_applications/{id}

import com.telnyx.sdk.models.faxapplications.FaxApplicationDeleteParams;
import com.telnyx.sdk.models.faxapplications.FaxApplicationDeleteResponse;

FaxApplicationDeleteResponse faxApplication = client.faxApplications().delete("1293384261075731499");

View a list of faxes

GET /faxes

import com.telnyx.sdk.models.faxes.FaxListPage;
import com.telnyx.sdk.models.faxes.FaxListParams;

FaxListPage page = client.faxes().list();

Returns: client_state (string), connection_id (string), created_at (date-time), direction (enum: inbound, outbound), from (string), from_display_name (string), id (uuid), media_name (string), media_url (string), preview_url (string), quality (enum: normal, high, very_high, ultra_light, ultra_dark), record_type (enum: fax), status (enum: queued, media.processed, originated, sending, delivered, failed, initiated, receiving, media.processing, received), store_media (boolean), stored_media_url (string), to (string), updated_at (date-time), webhook_failover_url (string), webhook_url (string)

Send a fax

Send a fax. Files have size limits and page count limit validations. If a file is bigger than 50MB or has more than 350 pages it will fail with file_size_limit_exceeded and page_count_limit_exceeded respectively.

POST /faxes — Required: connection_id, from, to

Optional: black_threshold (integer), client_state (string), from_display_name (string), media_name (string), media_url (string), monochrome (boolean), preview_format (enum: pdf, tiff), quality (enum: normal, high, very_high, ultra_light, ultra_dark), store_media (boolean), store_preview (boolean), t38_enabled (boolean), webhook_url (string)

import com.telnyx.sdk.models.faxes.FaxCreateParams;
import com.telnyx.sdk.models.faxes.FaxCreateResponse;

FaxCreateParams params = FaxCreateParams.builder()
    .connectionId("234423")
    .from("+13125790015")
    .to("+13127367276")
    .build();
FaxCreateResponse fax = client.faxes().create(params);

View a fax

GET /faxes/{id}

import com.telnyx.sdk.models.faxes.FaxRetrieveParams;
import com.telnyx.sdk.models.faxes.FaxRetrieveResponse;

FaxRetrieveResponse fax = client.faxes().retrieve("182bd5e5-6e1a-4fe4-a799-aa6d9a6ab26e");

Delete a fax

DELETE /faxes/{id}

import com.telnyx.sdk.models.faxes.FaxDeleteParams;

client.faxes().delete("182bd5e5-6e1a-4fe4-a799-aa6d9a6ab26e");

Cancel a fax

Cancel the outbound fax that is in one of the following states: queued, media.processed, originated or sending

POST /faxes/{id}/actions/cancel

import com.telnyx.sdk.models.faxes.actions.ActionCancelParams;
import com.telnyx.sdk.models.faxes.actions.ActionCancelResponse;

ActionCancelResponse response = client.faxes().actions().cancel("182bd5e5-6e1a-4fe4-a799-aa6d9a6ab26e");

Returns: result (string)

Refresh a fax

Refreshes the inbound fax's media_url when it has expired

POST /faxes/{id}/actions/refresh

import com.telnyx.sdk.models.faxes.actions.ActionRefreshParams;
import com.telnyx.sdk.models.faxes.actions.ActionRefreshResponse;

ActionRefreshResponse response = client.faxes().actions().refresh("182bd5e5-6e1a-4fe4-a799-aa6d9a6ab26e");

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
`fax.delivered`	Fax Delivered
`fax.failed`	Fax Failed
`fax.media.processed`	Fax Media Processed
`fax.queued`	Fax Queued
`fax.sending.started`	Fax Sending Started

Webhook payload fields

fax.delivered

Field	Type	Description
`data.record_type`	enum: event	Identifies the type of the resource.
`data.id`	uuid	Identifies the type of resource.
`data.occurred_at`	date-time	ISO 8601 datetime of when the event occurred.
`data.event_type`	enum: fax.delivered	The type of event being delivered.
`data.payload.call_duration_secs`	integer	The duration of the call in seconds.
`data.payload.connection_id`	string	The ID of the connection used to send the fax.
`data.payload.direction`	enum: inbound, outbound	The direction of the fax.
`data.payload.fax_id`	uuid	Identifies the fax.
`data.payload.original_media_url`	string	The original URL to the PDF used for the fax's media.
`data.payload.media_name`	string	The media_name used for the fax's media.
`data.payload.to`	string	The phone number, in E.164 format, the fax will be sent to or SIP URI
`data.payload.from`	string	The phone number, in E.164 format, the fax will be sent from.
`data.payload.user_id`	uuid	Identifier of the user to whom the fax belongs
`data.payload.page_count`	integer	Number of transferred pages
`data.payload.status`	enum: delivered	The status of the fax.
`data.payload.client_state`	string	State received from a command.
`meta.attempt`	integer	The delivery attempt number.
`meta.delivered_to`	uri	The URL the webhook was delivered to.

fax.failed

Field	Type	Description
`data.record_type`	enum: event	Identifies the type of the resource.
`data.id`	uuid	Identifies the type of resource.
`data.occurred_at`	date-time	ISO 8601 datetime of when the event occurred.
`data.event_type`	enum: fax.failed	The type of event being delivered.
`data.payload.connection_id`	string	The ID of the connection used to send the fax.
`data.payload.direction`	enum: inbound, outbound	The direction of the fax.
`data.payload.fax_id`	uuid	Identifies the fax.
`data.payload.original_media_url`	string	The original URL to the PDF used for the fax's media.
`data.payload.media_name`	string	The media_name used for the fax's media.
`data.payload.to`	string	The phone number, in E.164 format, the fax will be sent to or SIP URI
`data.payload.from`	string	The phone number, in E.164 format, the fax will be sent from.
`data.payload.user_id`	uuid	Identifier of the user to whom the fax belongs
`data.payload.failure_reason`	enum: rejected	Cause of the sending failure
`data.payload.status`	enum: failed	The status of the fax.
`data.payload.client_state`	string	State received from a command.
`meta.attempt`	integer	The delivery attempt number.
`meta.delivered_to`	uri	The URL the webhook was delivered to.

fax.media.processed

Field	Type	Description
`data.record_type`	enum: event	Identifies the type of the resource.
`data.id`	uuid	Identifies the type of resource.
`data.occurred_at`	date-time	ISO 8601 datetime of when the event occurred.
`data.event_type`	enum: fax.media.processed	The type of event being delivered.
`data.payload.connection_id`	string	The ID of the connection used to send the fax.
`data.payload.direction`	enum: inbound, outbound	The direction of the fax.
`data.payload.fax_id`	uuid	Identifies the fax.
`data.payload.original_media_url`	string	The original URL to the PDF used for the fax's media.
`data.payload.media_name`	string	The media_name used for the fax's media.
`data.payload.to`	string	The phone number, in E.164 format, the fax will be sent to or SIP URI
`data.payload.from`	string	The phone number, in E.164 format, the fax will be sent from.
`data.payload.user_id`	uuid	Identifier of the user to whom the fax belongs
`data.payload.status`	enum: media.processed	The status of the fax.
`data.payload.client_state`	string	State received from a command.
`meta.attempt`	integer	The delivery attempt number.
`meta.delivered_to`	uri	The URL the webhook was delivered to.

fax.queued

Field	Type	Description
`data.record_type`	enum: event	Identifies the type of the resource.
`data.id`	uuid	Identifies the type of resource.
`data.occurred_at`	date-time	ISO 8601 datetime of when the event occurred.
`data.event_type`	enum: fax.queued	The type of event being delivered.
`data.payload.connection_id`	string	The ID of the connection used to send the fax.
`data.payload.direction`	enum: inbound, outbound	The direction of the fax.
`data.payload.fax_id`	uuid	Identifies the fax.
`data.payload.original_media_url`	string	The original URL to the PDF used for the fax's media.
`data.payload.media_name`	string	The media_name used for the fax's media.
`data.payload.to`	string	The phone number, in E.164 format, the fax will be sent to or SIP URI
`data.payload.from`	string	The phone number, in E.164 format, the fax will be sent from.
`data.payload.user_id`	uuid	Identifier of the user to whom the fax belongs
`data.payload.status`	enum: queued	The status of the fax.
`data.payload.client_state`	string	State received from a command.
`meta.attempt`	integer	The delivery attempt number.
`meta.delivered_to`	uri	The URL the webhook was delivered to.

fax.sending.started

Field	Type	Description
`data.record_type`	enum: event	Identifies the type of the resource.
`data.id`	uuid	Identifies the type of resource.
`data.occurred_at`	date-time	ISO 8601 datetime of when the event occurred.
`data.event_type`	enum: fax.sending.started	The type of event being delivered.
`data.payload.connection_id`	string	The ID of the connection used to send the fax.
`data.payload.direction`	enum: inbound, outbound	The direction of the fax.
`data.payload.fax_id`	uuid	Identifies the fax.
`data.payload.original_media_url`	string	The original URL to the PDF used for the fax's media.
`data.payload.media_name`	string	The media_name used for the fax's media.
`data.payload.to`	string	The phone number, in E.164 format, the fax will be sent to or SIP URI
`data.payload.from`	string	The phone number, in E.164 format, the fax will be sent from.
`data.payload.user_id`	uuid	Identifier of the user to whom the fax belongs
`data.payload.status`	enum: sending	The status of the fax.
`data.payload.client_state`	string	State received from a command.
`meta.attempt`	integer	The delivery attempt number.
`meta.delivered_to`	uri	The URL the webhook was delivered to.

telnyx-fax-java