add global exception handler

workspaces/backend/src/main/java/org/raddatz/familienarchiv/controller/GlobalExceptionHandler.java

@@ -0,0 +1,40 @@
+package org.raddatz.familienarchiv.controller;
+
+import java.util.stream.Collectors;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+import org.springframework.web.server.ResponseStatusException;
+
+import lombok.extern.slf4j.Slf4j;
+
+@RestControllerAdvice
+@Slf4j
+public class GlobalExceptionHandler {
+
+    @ExceptionHandler(ResponseStatusException.class)
+    public ResponseEntity<ErrorResponse> handleStatus(ResponseStatusException ex) {
+        return ResponseEntity
+            .status(ex.getStatusCode())
+            .body(new ErrorResponse(ex.getReason()));
+    }
+
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ResponseEntity<ErrorResponse> handleValidation(MethodArgumentNotValidException ex) {
+        String message = ex.getBindingResult().getFieldErrors().stream()
+            .map(e -> e.getField() + ": " + e.getDefaultMessage())
+            .collect(Collectors.joining(", "));
+        return ResponseEntity.badRequest().body(new ErrorResponse(message));
+    }
+
+    @ExceptionHandler(Exception.class)
+    public ResponseEntity<ErrorResponse> handleGeneric(Exception ex) {
+        log.error("Unhandled exception", ex);
+        return ResponseEntity.internalServerError()
+            .body(new ErrorResponse("Ein Fehler ist aufgetreten"));
+    }
+
+    public record ErrorResponse(String message) {}
+}