Fix for IllegalArgumentException: URI is not absolute #12186

CHANGELOG.md

@@ -124,6 +124,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 - We fixed an issue when the preview was out of sync. [#9172](https://github.com/JabRef/jabref/issues/9172)
 - We fixed an issue where identifier paste couldn't work with Unicode REPLACEMENT CHARACTER. [#11986](https://github.com/JabRef/jabref/issues/11986)
 - We fixed an issue when click on entry at "Check Integrity" wasn't properly focusing the entry and field. [#11997](https://github.com/JabRef/jabref/issues/11997)
+- On saving a non-absolute URI, now a clear error message is shown. [#12186](https://github.com/JabRef/jabref/issues/12186)
 
 ### Removed
 

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

@@ -89,7 +89,11 @@ 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();
+        URI uri = createUri(url);
+        if (!uri.isAbsolute()) {
+            throw new MalformedURLException("URI is not absolute: " + url);
+        }
+        return uri.toURL();
     }
 
     /**

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.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+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 +92,22 @@ void createUriShouldHandlePipeCharacter() {
         URI uri = URLUtil.createUri(input);
         assertEquals("http://example.com/test%7Cfile", uri.toString());
     }
+
+    @Test
+    void createWithAbsoluteURL() {
+        String absoluteUrl = "http://www.example.com";
+        assertDoesNotThrow(() -> {
+            URL url = URLUtil.create(absoluteUrl);
+            assertNotNull(url);
+            assertEquals(absoluteUrl, url.toString());
+        }, "MalformedURLException should not be thrown for an absolute URL");
+    }
+
+    @Test
+    void createWithNonAbsoluteURL() {
+        String nonAbsoluteUrl = "www.example.com";
+        assertThrows(MalformedURLException.class, () -> {
+            URLUtil.create(nonAbsoluteUrl);
+        });
+    }
 }