added method FlatLaf.registerCustomDefaultsSource(URL packageUrl) for JPMS (issue #325)

CHANGELOG.md

@@ -50,6 +50,8 @@ FlatLaf Change Log
   applications: `lighten()`, `darken()`, `saturate()`, `desaturate()`, `spin()`,
   `tint()`, `shade()` and `luma()`.
 - Support defining fonts in FlatLaf properties files. (issue #384)
+- Added method `FlatLaf.registerCustomDefaultsSource(URL packageUrl)` for JPMS.
+  (issue #325)
 - Extras:
   - Added class `FlatDesktop` for easy integration into macOS screen menu
     (About, Preferences and Quit) when using Java 8.

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java

@@ -31,6 +31,7 @@ import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
 import java.io.File;
 import java.lang.reflect.Method;
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
@@ -753,6 +754,7 @@ public abstract class FlatLaf
 	 * Invoke this method before setting the look and feel.
 	 * <p>
 	 * If using Java modules, the package must be opened in {@code module-info.java}.
+	 * Otherwise use {@link #registerCustomDefaultsSource(URL)}.
 	 *
 	 * @param packageName a package name (e.g. "com.myapp.resources")
 	 */
@@ -794,6 +796,32 @@ public abstract class FlatLaf
 		}
 	}
 
+	/**
+	 * Registers a package where FlatLaf searches for properties files with custom UI defaults.
+	 * <p>
+	 * See {@link #registerCustomDefaultsSource(String)} for details.
+	 * <p>
+	 * This method is useful if using Java modules and the package containing the properties files
+	 * is not opened in {@code module-info.java}.
+	 * E.g. {@code FlatLaf.registerCustomDefaultsSource( MyApp.class.getResource( "/com/myapp/themes/" ) )}.
+	 *
+	 * @param packageUrl a package URL
+	 * @since 2
+	 */
+	public static void registerCustomDefaultsSource( URL packageUrl ) {
+		if( customDefaultsSources == null )
+			customDefaultsSources = new ArrayList<>();
+		customDefaultsSources.add( packageUrl );
+	}
+
+	/** @since 2 */
+	public static void unregisterCustomDefaultsSource( URL packageUrl ) {
+		if( customDefaultsSources == null )
+			return;
+
+		customDefaultsSources.remove( packageUrl );
+	}
+
 	/**
 	 * Registers a folder where FlatLaf searches for properties files with custom UI defaults.
 	 * <p>

flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java

@@ -22,10 +22,12 @@ import java.awt.Font;
 import java.awt.Insets;
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.StreamTokenizer;
 import java.io.StringReader;
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -156,6 +158,18 @@ class UIDefaultsLoader
 								properties.load( in );
 						}
 					}
+				} else if( source instanceof URL ) {
+					// load from package URL
+					URL packageUrl = (URL) source;
+					for( Class<?> lafClass : lafClasses ) {
+						URL propertiesUrl = new URL( packageUrl + lafClass.getSimpleName() + ".properties" );
+
+						try( InputStream in = propertiesUrl.openStream() ) {
+							properties.load( in );
+						} catch( FileNotFoundException ex ) {
+							// ignore
+						}
+					}
 				} else if( source instanceof File ) {
 					// load from folder
 					File folder = (File) source;