Fix ClassCastException when creating new class from Direct Menu Item

Creating a new class via the "Class URI" link in the E4 application
model
editor threw a ClassCastException due to an invalid type conversion in
the
data binding configuration of AbstractNewClassPage.java.

The target-to-model UpdateValueStrategy was missing a converter to
transform
the String value from the text field into an IPackageFragmentRoot,
leading
to a failed cast by the default converter.

This change introduces StringToPackageFragmentRootConverter to properly
map String paths to IPackageFragmentRoot instances and integrates it
into
the data binding setup. Users can now open the new class wizard and
create
handler classes without errors.

Author: vogella

e4tools/bundles/org.eclipse.e4.tools/src/org/eclipse/e4/internal/tools/wizards/classes/AbstractNewClassPage.java

@@ -253,6 +253,7 @@ public void createControl(Composite parent) {
 					WidgetProperties.text().observe(t),
 					BeanProperties.value(FRAGMENT_ROOT, IPackageFragmentRoot.class).observe(clazz),
 					new UpdateValueStrategy<String, IPackageFragmentRoot>()
+					.setConverter(new StringToPackageFragmentRootConverter(fWorkspaceRoot))
 					.setBeforeSetValidator(new PFRootValidator()),
 					UpdateValueStrategy.create(new PackageFragmentRootToStringConverter()));
 
@@ -585,4 +586,37 @@ public IPackageFragment convert(String fromObject) {
 
 		}
 	}
+
+	static class StringToPackageFragmentRootConverter extends Converter<String, IPackageFragmentRoot> {
+
+		private final IWorkspaceRoot workspaceRoot;
+
+		public StringToPackageFragmentRootConverter(IWorkspaceRoot workspaceRoot) {
+			super(String.class, IPackageFragmentRoot.class);
+			this.workspaceRoot = workspaceRoot;
+		}
+
+		@Override
+		public IPackageFragmentRoot convert(String fromObject) {
+			if (fromObject == null || fromObject.isEmpty()) {
+				return null;
+			}
+
+			try {
+				IJavaModel javaModel = JavaCore.create(workspaceRoot);
+				// Try to find the package fragment root by its path
+				for (IJavaProject javaProject : javaModel.getJavaProjects()) {
+					for (IPackageFragmentRoot root : javaProject.getPackageFragmentRoots()) {
+						if (root.getPath().makeRelative().toString().equals(fromObject)) {
+							return root;
+						}
+					}
+				}
+			} catch (JavaModelException e) {
+				// Return null if conversion fails
+			}
+
+			return null;
+		}
+	}
 }