Support multiple properties files with a certain name in HapiLocalizer (#7141)

* Try multi-file resolution

* Make inner class static and spotless.

* Messy fix for ResourceBundle.Control:  1) Disregard properties files for non-root locales (by overriding a couple of methods). 2) Fix the I/O to read the Properties objects since the old code with StringReader was truncating the properties.

* Add new test.

* Refactor ResourceBundle.Control implementation to be more efficient and extract it to its own class, with a backing custom ResourceBundle implementation.

---------

Co-authored-by: Michael Buckley <[email protected]>

Author: lukedegruchy

hapi-fhir-base/src/main/java/ca/uhn/fhir/i18n/HapiLocalizer.java

@@ -22,6 +22,7 @@
 import ca.uhn.fhir.context.ConfigurationException;
 import ca.uhn.fhir.util.UrlUtil;
 import ca.uhn.fhir.util.VersionUtil;
+import com.google.common.annotations.VisibleForTesting;
 
 import java.text.MessageFormat;
 import java.util.ArrayList;
@@ -169,7 +170,7 @@ MessageFormat newMessageFormat(String theFormatString) {
 	protected void init(String[] theBundleNames) {
 		myBundle = new ArrayList<>();
 		for (String nextName : theBundleNames) {
-			myBundle.add(ResourceBundle.getBundle(nextName));
+			myBundle.add(ResourceBundle.getBundle(nextName, new MultiFileResourceBundleControl()));
 		}
 	}
 
@@ -189,4 +190,9 @@ public static void setOurFailOnMissingMessage(boolean ourFailOnMissingMessage) {
 	public static String toKey(Class<?> theType, String theKey) {
 		return theType.getName() + '.' + theKey;
 	}
+
+	@VisibleForTesting
+	List<ResourceBundle> getBundles() {
+		return myBundle;
+	}
 }

hapi-fhir-base/src/main/java/ca/uhn/fhir/i18n/MultiFileResourceBundleControl.java

@@ -0,0 +1,94 @@
+package ca.uhn.fhir.i18n;
+
+import jakarta.annotation.Nonnull;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Locale;
+import java.util.Properties;
+import java.util.ResourceBundle;
+
+/**
+ * Finds all properties files on the class path that match the given base name and merges them.
+ * This implementation avoids the unnecessary overhead of writing to and reading from a stream.
+ */
+public class MultiFileResourceBundleControl extends ResourceBundle.Control {
+
+	/**
+	 * Returns a list containing only Locale.ROOT as a candidate.
+	 * This forces the loader to look for the base bundle only (e.g., "bundle.properties").
+	 *
+	 * @param baseName the base name of the resource bundle
+	 * @param locale   the locale to load (this parameter is ignored)
+	 * @return a singleton list containing Locale.ROOT
+	 */
+	@Override
+	public List<Locale> getCandidateLocales(String baseName, Locale locale) {
+		return Collections.singletonList(Locale.ROOT);
+	}
+
+	/**
+	 * Prevents fallback to the default locale if the root bundle isn't found.
+	 *
+	 * @param baseName the base name of the resource bundle
+	 * @param locale   the locale where the search is failing
+	 * @return null to indicate no fallback should be attempted
+	 */
+	@Override
+	public Locale getFallbackLocale(String baseName, Locale locale) {
+		return null;
+	}
+
+	@Override
+	public ResourceBundle newBundle(String baseName, Locale locale, String format, ClassLoader loader, boolean reload)
+			throws IOException, IllegalAccessException, InstantiationException {
+
+		// We only care about handling the root .properties file
+		if (!"java.properties".equals(format)
+				|| (locale != null && !locale.toString().isEmpty())) {
+			return super.newBundle(baseName, locale, format, loader, reload);
+		}
+
+		final String resourceName = toResourceName(toBundleName(baseName, locale), "properties");
+		final Properties mergedProperties = new Properties();
+
+		// Load from all matching resources
+		final Enumeration<URL> resources = loader.getResources(resourceName);
+		while (resources.hasMoreElements()) {
+			final URL url = resources.nextElement();
+
+			try (InputStream is = url.openStream()) {
+				mergedProperties.load(is);
+			}
+		}
+
+		// Directly wrap the merged Properties object instead of performing a stream round-trip.
+		return new PropertiesResourceBundle(mergedProperties);
+	}
+
+	/**
+	 * A lightweight, private ResourceBundle implementation that is backed directly by a Properties object.
+	 */
+	private static class PropertiesResourceBundle extends ResourceBundle {
+		private final Properties properties;
+
+		PropertiesResourceBundle(Properties properties) {
+			this.properties = properties;
+		}
+
+		@Override
+		protected Object handleGetObject(@Nonnull String key) {
+			return properties.getProperty(key);
+		}
+
+		@Override
+		@Nonnull
+		public Enumeration<String> getKeys() {
+			return Collections.enumeration(properties.stringPropertyNames());
+		}
+	}
+}

hapi-fhir-base/src/test/java/ca/uhn/fhir/i18n/HapiLocalizerTest.java

@@ -2,6 +2,10 @@
 
 import org.junit.jupiter.api.Test;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ResourceBundle;
 import java.util.Set;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -36,5 +40,24 @@ public void testGetVersion() {
 		String version = svc.getMessage("hapi.version");
 		assertThat(version).matches("[0-9]+.*");
 	}
-	
+
+	@Test
+	void multiFileBundles() {
+		final HapiLocalizer hapiLocalizer = new HapiLocalizer();
+		final List<ResourceBundle> bundles = hapiLocalizer.getBundles();
+		assertThat(bundles).isNotNull().hasSize(1);
+
+		final ResourceBundle onlyResourceBundle = bundles.get(0);
+		final List<String> keysAsList = Collections.list(onlyResourceBundle.getKeys());
+
+		// From the main hapi-messages file
+		assertThat(keysAsList)
+			.contains("ca.uhn.fhir.jpa.dao.index.IdHelperService.nonUniqueForcedId");
+		// From the hapi-messages file in the test resources
+		assertThat(keysAsList).contains("foo");
+
+		assertThat(onlyResourceBundle.getString("ca.uhn.fhir.jpa.dao.index.IdHelperService.nonUniqueForcedId")).isEqualTo("Non-unique ID specified, can not process request");
+		// And we get the expected value from the test resource
+		assertThat(onlyResourceBundle.getString("foo")).isEqualTo("bar");
+	}
 }

hapi-fhir-base/src/test/resources/ca/uhn/fhir/i18n/hapi-messages.properties

@@ -0,0 +1 @@
+foo=bar