[GitHub] [commons-configuration] darkma773r commented on a diff in pull request #181: CONFIGURATION-753: Interpolation Consistency

[GitBox <gi...@apache.org>]

darkma773r commented on code in PR #181:
URL: https://github.com/apache/commons-configuration/pull/181#discussion_r874326998


##########
src/main/java/org/apache/commons/configuration2/interpol/ConfigurationInterpolator.java:
##########
@@ -452,4 +511,51 @@ public void setEnableSubstitutionInVariables(final boolean f) {
     public void setParentInterpolator(final ConfigurationInterpolator parentInterpolator) {
         this.parentInterpolator = parentInterpolator;
     }
+
+    /** Class encapsulating the default logic to convert resolved variable values into strings.
+     * This class is thread-safe.
+     */
+    private static final class DefaultStringConverter implements Function<Object, String> {
+
+        /** Shared instance. */
+        static final DefaultStringConverter INSTANCE = new DefaultStringConverter();
+
+        /** {@inheritDoc} */
+        @Override
+        public String apply(final Object obj) {
+            return Objects.toString(extractSimpleValue(obj), null);
+        }
+
+        /** Attempt to extract a simple value from {@code obj} for use in string conversion.
+         * If the input represents a collection of some sort (e.g., an iterable or array),
+         * the first item from the collection is returned.
+         * @param obj input object
+         * @return extracted simple object
+         */
+        private Object extractSimpleValue(final Object obj) {
+            if (!(obj instanceof String)) {
+                if (obj instanceof Iterable) {
+                   return nextOrNull(((Iterable<?>) obj).iterator());
+                } else if (obj instanceof Iterator) {
+                    return nextOrNull((Iterator<?>) obj);
+                } else if (obj.getClass().isArray()) {
+                    return Array.getLength(obj) > 0
+                            ? Array.get(obj, 0)
+                            : null;

Review Comment:
   I only see `ArrayUtils.get` methods that accept `T[]` instead of `Object` so I think I need to stick with the current implementation.



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