adding field error validation

src/main/java/com/homihq/db2rest/exception/GlobalExceptionHandler.java

@@ -1,9 +1,40 @@
 package com.homihq.db2rest.exception;
 
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.annotation.RestControllerAdvice;
+import org.springframework.web.context.request.ServletWebRequest;
+import org.springframework.web.context.request.WebRequest;
 import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
 
+import java.time.Instant;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+
 @RestControllerAdvice
 public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
 
+    @Override
+    protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex,
+                                                                  HttpHeaders headers,
+                                                                  HttpStatusCode status, WebRequest request) {
+        var body = new LinkedHashMap<>();
+        body.put("type", "https://github.com/kdhrubo/db2rest/invalid-arguments");
+        body.put("title", "Invalid arguments in the request");
+        body.put("status", status.value());
+        var errors = ex.getBindingResult()
+                .getFieldErrors()
+                .stream()
+                .map(error -> Map.of(error.getField(), Objects.requireNonNull(error.getDefaultMessage())))
+                .toList();
+        body.put("detail", errors);
+        body.put("instance", ((ServletWebRequest) request).getRequest().getRequestURI());
+        body.put("errorCategory", "Invalid-Arguments");
+        body.put("timestamp", Instant.now());
+        return new ResponseEntity<>(body, headers, status);
+    }
+
 }