fix: Read Hilla version from correct file (#18807)

* fix: Read Hilla version from correct file

Fixes vaadin/platform#5014

* Update Platform.java

Author: Artur-

flow-server/src/main/java/com/vaadin/flow/server/Platform.java

@@ -29,6 +29,7 @@
  * @since 23.0
  */
 public class Platform implements Serializable {
+    static final String HILLA_POM_PROPERTIES = "META-INF/maven/com.vaadin/hilla/pom.properties";
     private static final Logger LOGGER = LoggerFactory
             .getLogger(Platform.class);
     /**
@@ -87,15 +88,15 @@ public static Optional<String> getHillaVersion() {
         // immutable and thread-safe.
         if (hillaVersion == null) {
             try (final InputStream hillaPomProperties = Thread.currentThread()
-                    .getContextClassLoader().getResourceAsStream(
-                            "META-INF/maven/com.vaadin.hilla/hilla/pom.properties")) {
+                    .getContextClassLoader()
+                    .getResourceAsStream(HILLA_POM_PROPERTIES)) {
                 if (hillaPomProperties != null) {
                     final Properties properties = new Properties();
                     properties.load(hillaPomProperties);
                     hillaVersion = properties.getProperty("version", "");
                 } else {
                     LOGGER.info("Unable to determine Hilla version. "
-                            + "No META-INF/maven/com.vaadin.hilla/hilla/pom.properties found");
+                            + "No {} found", HILLA_POM_PROPERTIES);
                     hillaVersion = "";
                 }
             } catch (Exception e) {

flow-server/src/test/java/com/vaadin/flow/server/PlatformTest.java

@@ -64,8 +64,8 @@ private void fakeVaadinHilla(String vaadinVersion, String hillaVersion)
 
         if (hillaVersion != null) {
             final Path hillaJar = temporary.newFolder().toPath();
-            final Path pomProperties = hillaJar.resolve(
-                    "META-INF/maven/com.vaadin.hilla/hilla/pom.properties");
+            final Path pomProperties = hillaJar
+                    .resolve(Platform.HILLA_POM_PROPERTIES);
             Files.createDirectories(pomProperties.getParent());
             Files.writeString(pomProperties, "version=" + hillaVersion);
             classPath.add(hillaJar.toUri().toURL());