Response
Here's the full implementation: the service, three domain exceptions, the `@RestControllerAdvice` handler that turns them into HTTP responses, and a thin controller + `ApiResponse` wrapper so the flow is complete end-to-end.
```java
package com.acme.billing;
/**
* Thrown when an invoice cannot be found for the given id.
*/
public class InvoiceNotFoundException extends RuntimeException {
public InvoiceNotFoundException(long invoiceId) {
super("Invoice " + invoiceId + " was not found");
}
}
```
```java
package com.acme.billing;
/**
* Thrown when a customer attempts to act on an invoice that does not belong to them.
*/
public class InvoiceAccessDeniedException extends RuntimeException {
public InvoiceAccessDeniedException(long invoiceId) {
super("Invoice " + invoiceId + " does not belong to the requesting customer");
}
}
```
```java
package com.acme.billing;
/**
* Thrown when an invoice is no longer in a cancellable state.
*/
public class InvoiceNotCancellableException extends RuntimeException {
public InvoiceNotCancellableException(long invoiceId, InvoiceStatus status) {
super("Invoice " + invoiceId + " cannot be cancelled because it is " + status);
}
}
```
```java
package com.acme.billing;
import org.springframework.stereotype.Service;
@Service
public class InvoiceService {
private final InvoiceRepository invoiceRepository;
public InvoiceService(InvoiceRepository invoiceRepository) {
this.invoiceRepository = invoiceRepository;
}
public void cancelInvoice(long invoiceId, long customerId) {
Invoice invoice = invoiceRepository.findById(invoiceId)
.orElseThrow(() -> new InvoiceNotFoundException(invoiceId));
if (invoice.customerId() != customerId) {
throw new InvoiceAccessDeniedException(invoiceId);
}
if (invoice.status() != InvoiceStatus.UNPAID) {
throw new InvoiceNotCancellableException(invoiceId, invoice.status());
}
invoice.markCancelled();
}
}
```
```java
package com.acme.billing;
/**
* Standard response envelope. Controllers never return raw entities or bare lists.
*/
public record ApiResponse<T>(boolean success, T data, ApiError error) {
public static <T> ApiResponse<T> ok(T data) {
return new ApiResponse<>(true, data, null);
}
public static <T> ApiResponse<T> error(String code, String message) {
return new ApiResponse<>(false, null, new ApiError(code, message));
}
public record ApiError(String code, String message) {}
}
```
```java
package com.acme.billing;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
@RestControllerAdvice
public class BillingExceptionHandler {
@ExceptionHandler(InvoiceNotFoundException.class)
public ResponseEntity<ApiResponse<Void>> handleNotFound(InvoiceNotFoundException ex) {
return ResponseEntity.status(HttpStatus.NOT_FOUND)
.body(ApiResponse.error("INVOICE_NOT_FOUND", ex.getMessage()));
}
@ExceptionHandler(InvoiceAccessDeniedException.class)
public ResponseEntity<ApiResponse<Void>> handleAccessDenied(InvoiceAccessDeniedException ex) {
return ResponseEntity.status(HttpStatus.FORBIDDEN)
.body(ApiResponse.error("INVOICE_ACCESS_DENIED", ex.getMessage()));
}
@ExceptionHandler(InvoiceNotCancellableException.class)
public ResponseEntity<ApiResponse<Void>> handleNotCancellable(InvoiceNotCancellableException ex) {
return ResponseEntity.status(HttpStatus.CONFLICT)
.body(ApiResponse.error("INVOICE_NOT_CANCELLABLE", ex.getMessage()));
}
}
```
```java
package com.acme.billing;
import org.springframework.security.core.annotation.AuthenticationPrincipal;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/api/invoices")
public class InvoiceController {
private final InvoiceService invoiceService;
public InvoiceController(InvoiceService invoiceService) {
this.invoiceService = invoiceService;
}
@PostMapping("/{id}/cancel")
public ApiResponse<Void> cancel(@PathVariable("id") long id,
@AuthenticationPrincipal long customerId) {
invoiceService.cancelInvoice(id, customerId);
return ApiResponse.ok(null);
}
}
```
Convention notes:
- Constructor injection, thin controller delegating to the service, and authorization living in the service (not just the route) all follow the house rules; `@AuthenticationPrincipal long customerId` is a placeholder for however this codebase resolves the current customer — swap it for the real mechanism.
- Assumed `InvoiceStatus` is an existing enum on `Invoice` (with an `UNPAID` value) and that `ApiResponse` doesn't already exist elsewhere in the codebase — if it does, drop the copy above and reuse it.