bff/pom.xml

@@ -32,6 +32,10 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-oauth2-client</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-validation</artifactId>
+        </dependency>
 
         <!-- OpenAPI specification -->
         <dependency>

bff/src/main/java/se/su/dsv/studentportalen/bff/exception/GlobalExceptionHandler.java

@@ -0,0 +1,85 @@
+package se.su.dsv.studentportalen.bff.exception;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ProblemDetail;
+import org.springframework.validation.FieldError;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+
+import java.net.URI;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/**
+ * Centralized exception handler for all REST controllers.
+ * Returns RFC 7807 Problem Details for all error responses.
+ */
+@RestControllerAdvice
+public class GlobalExceptionHandler {
+
+    private static final Logger LOG = LoggerFactory.getLogger(GlobalExceptionHandler.class);
+
+    /**
+     * Handles Jakarta Bean Validation errors (missing/invalid fields).
+     * Triggered when @Valid fails on request body.
+     */
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ProblemDetail handleValidation(MethodArgumentNotValidException ex) {
+        Map<String, List<String>> violations = ex.getBindingResult().getFieldErrors().stream()
+                .collect(Collectors.groupingBy(
+                        FieldError::getField,
+                        Collectors.mapping(
+                                error -> error.getDefaultMessage() != null ? error.getDefaultMessage() : "Invalid value",
+                                Collectors.toList()
+                        )
+                ));
+
+        LOG.warn("Validation failed: {}", violations);
+
+        ProblemDetail problem = ProblemDetail.forStatus(HttpStatus.BAD_REQUEST);
+        problem.setType(URI.create("studentportalen:validation-error"));
+        problem.setTitle("Validation failed");
+        problem.setDetail("One or more fields are invalid");
+        problem.setProperty("violations", violations);
+        return problem;
+    }
+
+    /**
+     * Handles business exceptions from the BFF.
+     * These include mapped errors from backend systems like Daisy.
+     */
+    @ExceptionHandler(StudentportalenException.class)
+    public ProblemDetail handleBusinessError(StudentportalenException ex) {
+        LOG.warn("Business error: {} - {}", ex.getType(), ex.getMessage());
+
+        ProblemDetail problem = ProblemDetail.forStatus(ex.getStatus());
+        problem.setType(URI.create(ex.getType()));
+        problem.setTitle(ex.getTitle());
+        problem.setDetail(ex.getMessage());
+
+        if (ex instanceof ValidationException ve && !ve.getViolations().isEmpty()) {
+            problem.setProperty("violations", ve.getViolations());
+        }
+
+        return problem;
+    }
+
+    /**
+     * Handles unexpected errors.
+     * Logs the full stack trace but returns a generic message to the client.
+     */
+    @ExceptionHandler(Exception.class)
+    public ProblemDetail handleUnexpected(Exception ex) {
+        LOG.error("Unexpected error", ex);
+
+        ProblemDetail problem = ProblemDetail.forStatus(HttpStatus.INTERNAL_SERVER_ERROR);
+        problem.setType(URI.create("studentportalen:internal-error"));
+        problem.setTitle("An unexpected error occurred");
+        problem.setDetail("Please try again later");
+        return problem;
+    }
+}