Support HTTPS, FTP, and FTPS resource URLs in Declarative (#17267)

Manually picked to 7.4 from commit b96861c in master, also added a test.

Change-Id: I415f7409084ea0abd8b22ba3892743e11d503c27

server/src/com/vaadin/ui/declarative/converters/DesignResourceConverter.java

@@ -39,7 +39,8 @@ public class DesignResourceConverter implements Converter<String, Resource> {
     public Resource convertToModel(String value,
             Class<? extends Resource> targetType, Locale locale)
             throws Converter.ConversionException {
-        if (value.startsWith("http://")) {
+        if (value.startsWith("http://") || value.startsWith("https://")
+                || value.startsWith("ftp://") || value.startsWith("ftps://")) {
             return new ExternalResource(value);
         } else if (value.startsWith("theme://")) {
             return new ThemeResource(value.substring(8));

server/tests/src/com/vaadin/tests/design/DesignFormatterTest.java

@@ -227,6 +227,25 @@ public void testTimeZone() {
         assertEquals(zone, result);
     }
 
+    @Test
+    public void testExternalResource() {
+        String url = "://example.com/my%20icon.png?a=b";
+
+        for (String scheme : new String[] { "http", "https", "ftp", "ftps" }) {
+            Resource resource = formatter.parse(scheme + url, Resource.class);
+
+            assertTrue(scheme + " url should be parsed as ExternalResource",
+                    resource instanceof ExternalResource);
+            assertEquals("parsed ExternalResource", scheme + url,
+                    ((ExternalResource) resource).getURL());
+
+            String formatted = formatter.format(new ExternalResource(scheme
+                    + url));
+
+            assertEquals("formatted ExternalResource", scheme + url, formatted);
+        }
+    }
+
     /**
      * A static method to allow comparison two different actions.
      *