Start Here

Java error handling

Check ApiResponse envelopes, read Core error bodies, and handle validation and transport failures with the Java SDK.

Every SDK method returns an ApiResponse. The SDK does not throw on API failures. Check status() before you use data().

On success, data() holds the resource. On failure, status() and message() describe what went wrong. error() holds structured Core error details when available. data() may hold Core’s raw error JSON or be null.

Parse the response

Read the envelope first. Use status() to classify the failure, then read the field that carries detail for that type.

public record BlnkApiErrorDetail(String code, String message, Object details) {}

public record ApiResponse<T>(int status, String message, T data, BlnkApiErrorDetail error) {}

Property	Contains
`status()`	HTTP-style codes: 2xx success, 4xx client error, etc.
`data()`	Success body, or Core error JSON on rejection. May be `null`.
`error()`	Structured error parsed from Core’s `error_detail`. Use `error().code()` for logic.
`message()`	Human-readable description. For logs and UI only. Do not use for logic.

How to handle errors

Check status

Confirm success before you use data(). On every call, check that status() is in the 2xx range for the method you called.

ApiResponse<JsonNode> response = blnk.transactions().get(
    "txn_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94"
);

if (response.status() < 200 || response.status() >= 300) {
  String errorCode = response.error() != null ? response.error().code() : null;

  if (response.status() == 404) {
    // Resource not found: check errorCode (e.g. TXN_NOT_FOUND)
  } else if (response.status() == 401 || response.status() == 403) {
    // Auth or scope failure: check the API key
  } else {
    // Log status, errorCode, and response.message()
  }
} else {
  // Use response.data()
}

Read the error detail

Use the field that matches the failure type:

Core rejection (status() is a Core HTTP error and data() is set): read response.error().code() for the code Core returned.
SDK validation (status() == 400 and data() is null): read response.message() and fix the payload before retrying.

Route on response.status() when you do not need code-level logic (401, 404, 409, 5xx).

Configure transport handling

When the SDK cannot reach Core or the request times out, you get status() 408 or 500 and data() null.

Configure timeout and logging in your SDK client to investigate these failures.

Core errors

When Core rejects a request, the SDK wraps the failure in an ApiResponse. It sets status() to Core’s HTTP status, message() to the error message, data() to Core’s JSON error body, and error() to structured details parsed from error_detail.

On Core 0.15.0 and later, a rejected request looks like this:

ApiResponse<JsonNode> response = blnk.transactions().get("txn_missing");

// response:
// status=404
// message="transaction not found"
// data={ "error": "...", "error_detail": { "code": "TXN_NOT_FOUND", ... } }
// error=BlnkApiErrorDetail(code="TXN_NOT_FOUND", message="transaction not found", details={})

The SDK exports these codes as BlnkErrorCodes:

Constant	When Core returns it
`BlnkErrorCodes.TXN_VALIDATION_ERROR`	Negative amount or precision, or source equal to destination
`BlnkErrorCodes.GEN_CONFLICT`	Duplicate General Ledger indicator and currency (`409`)
`BlnkErrorCodes.TXN_INVALID_AMOUNT`	Invalid amount (see the API error codes catalog)

Use response.status() to pick the first branch (not found, auth, conflict, bad request, or server failure). Then use response.error().code() for the specific case.

Status	When it happens	What to do
`404`	Resource ID or path does not exist	Check `response.error().code()` (e.g. `TXN_NOT_FOUND`, `IDT_NOT_FOUND`)
`401` or `403`	API key, scope, or permission failure	Check the key, scopes, and whether the method requires the master key
`409`	Conflict (duplicate reference, lock, or in-progress job)	Retry only if the operation is safe to repeat
`400`	Core rejected the payload	Fix the request body before retrying
`5xx`	Core or upstream failure	Retry later and check Core logs

Client-side validation

Some methods validate input before sending a request. When validation fails, Core never receives the call.

Field	Value
`status()`	`400`
`message()`	Validation error string, e.g. `reference field must be a valid string`
`data()`	`null`
`error()`	`null`

Transport failures

When the SDK cannot reach Core or the request times out, you get status() 408 or 500, data() null, and a message() describing the failure. Configure timeout and logging in Using the SDK.

When debugging transport failures, log status(), message(), and the endpoint you called.