Refine error message in URLUtil::create

jablib/src/main/java/org/jabref/logic/util/URLUtil.java

@@ -97,7 +97,21 @@ public static boolean isURL(String url) {
      * @throws MalformedURLException if the URL is malformed and cannot be converted to a {@link URL}.
      */
     public static URL create(String url) throws MalformedURLException {
-        return createUri(url).toURL();
+        if (url == null || url.trim().isEmpty()) {
+            throw new IllegalArgumentException("URL must not be null or empty.");
+        }
+        try {
+            URI parsedUri = new URI(url.trim());
+            if (!parsedUri.isAbsolute()) {
+                throw new MalformedURLException("URI is not absolute: " + url);
+            }
+            if (parsedUri.getScheme() == null || parsedUri.getHost() == null) {
+                throw new MalformedURLException("URI must include both scheme and host: " + url);
+            }
+            return parsedUri.toURL();
+        } catch (URISyntaxException | IllegalArgumentException e) {
+            throw new MalformedURLException("Invalid URI: " + url + " | " + e.getMessage());
+        }
     }
 
     /**

jablib/src/test/java/org/jabref/logic/net/URLUtilTest.java

@@ -1,13 +1,18 @@
 package org.jabref.logic.net;
 
+import java.net.MalformedURLException;
 import java.net.URI;
+import java.net.URL;
 
 import org.jabref.logic.util.URLUtil;
 
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class URLUtilTest {
@@ -87,4 +92,49 @@ void createUriShouldHandlePipeCharacter() {
         URI uri = URLUtil.createUri(input);
         assertEquals("http://example.com/test%7Cfile", uri.toString());
     }
+
+    @Test
+    public void validUrl() throws MalformedURLException {
+        String input = "http://example.com";
+
+        URL result = URLUtil.create(input);
+        assertNotNull(result);
+        assertNotEquals("", result.toString().trim());
+        assertEquals(input, result.toString());
+    }
+
+    @Test
+    public void nullUrl() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () ->
+                URLUtil.create(null));
+        assertTrue(exception.getMessage().contains("null or empty"));
+    }
+
+    @Test
+    public void emptyUrl() {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () ->
+                URLUtil.create("   "));
+        assertTrue(exception.getMessage().contains("null or empty"));
+    }
+
+    @Test
+    public void uriMissingScheme() {
+        MalformedURLException exception = assertThrows(MalformedURLException.class, () ->
+                URLUtil.create("www.example.com"));
+        assertTrue(exception.getMessage().contains("not absolute"));
+    }
+
+    @Test
+    public void uriMissingHost() {
+        MalformedURLException exception = assertThrows(MalformedURLException.class, () ->
+                URLUtil.create("mailto:[email protected]"));
+        assertTrue(exception.getMessage().contains("must include both scheme and host"));
+    }
+
+    @Test
+    public void malformedSyntax() {
+        MalformedURLException exception = assertThrows(MalformedURLException.class, () ->
+                URLUtil.create("http://[invalid-url]"));
+        assertTrue(exception.getMessage().contains("Invalid URI"));
+    }
 }