#1019 - Improvements to I18N optimizations.

We now properly look for resource bundles by scanning for a resource bundle *pattern* instead of a plain file named rest-messages. Added integration tests to make sure that resource bundles are not skipped even if they existed.

Added the ability to define common messages in a rest-default-messages.properties, as Spring Data REST requires that and it would be too cumbersome for Spring Data REST to additionally deploy them in its own configuration.

src/main/java/org/springframework/hateoas/config/HateoasConfiguration.java

@@ -15,14 +15,26 @@
  */
 package org.springframework.hateoas.config;
 
-import org.springframework.context.MessageSource;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Properties;
+import java.util.stream.Collectors;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.PropertiesFactoryBean;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Primary;
+import org.springframework.context.support.AbstractMessageSource;
 import org.springframework.context.support.AbstractResourceBasedMessageSource;
 import org.springframework.context.support.ReloadableResourceBundleMessageSource;
-import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
 import org.springframework.hateoas.client.LinkDiscoverer;
 import org.springframework.hateoas.client.LinkDiscoverers;
 import org.springframework.hateoas.mediatype.MessageResolver;
@@ -50,7 +62,9 @@ import org.springframework.util.ClassUtils;
 @Configuration
 @Import(EntityLinksConfiguration.class)
 @EnablePluginRegistries({ LinkDiscoverer.class })
-class HateoasConfiguration {
+public class HateoasConfiguration {
+
+	private @Autowired ApplicationContext context;
 
 	@Bean
 	public MessageResolver messageResolver() {
@@ -104,17 +118,53 @@ class HateoasConfiguration {
 	 * @return will never be {@literal null}.
 	 */
 	@Nullable
-	private static final MessageSource lookupMessageSource() {
+	private final AbstractMessageSource lookupMessageSource() {
 
-		ClassPathResource resource = new ClassPathResource("rest-messages");
+		List<Resource> candidates = loadProperties("rest-default-messages", false);
 
-		if (!resource.exists()) {
+		if (candidates.isEmpty() && loadProperties("rest-messages", true).isEmpty()) {
 			return null;
 		}
 
 		AbstractResourceBasedMessageSource messageSource = new ReloadableResourceBundleMessageSource();
 		messageSource.setBasename("classpath:rest-messages");
+		messageSource.setDefaultEncoding(StandardCharsets.UTF_8.toString());
+
+		if (!candidates.isEmpty()) {
+			messageSource.setCommonMessages(loadProperties(candidates));
+		}
 
 		return messageSource;
 	}
+
+	@Nullable
+	private final Properties loadProperties(Collection<Resource> sources) {
+
+		Resource[] resources = loadProperties("rest-default-messages", false).stream().toArray(Resource[]::new);
+
+		PropertiesFactoryBean factory = new PropertiesFactoryBean();
+		factory.setLocations(resources);
+
+		try {
+
+			factory.afterPropertiesSet();
+			return factory.getObject();
+
+		} catch (IOException o_O) {
+			throw new IllegalStateException("Could not load default properties from resources!", o_O);
+		}
+	}
+
+	private final List<Resource> loadProperties(String baseName, boolean withWildcard) {
+
+		try {
+			return Arrays //
+					.stream(context.getResources(String.format("classpath:%s%s.properties", baseName, withWildcard ? "*" : ""))) //
+					.filter(Resource::exists) //
+					.collect(Collectors.toList());
+
+		} catch (IOException e) {
+			return Collections.emptyList();
+		}
+	}
 }

src/main/java/org/springframework/hateoas/mediatype/DefaultOnlyMessageResolver.java

@@ -18,7 +18,12 @@ package org.springframework.hateoas.mediatype;
 import org.springframework.context.MessageSourceResolvable;
 import org.springframework.lang.Nullable;
 
-enum NoMessageResolver implements MessageResolver {
+/**
+ * {@link MessageResolver} to always resort to the {@link MessageSourceResolvable}'s default message.
+ *
+ * @author Oliver Drotbohm
+ */
+enum DefaultOnlyMessageResolver implements MessageResolver {
 
 	INSTANCE;
 
@@ -29,6 +34,6 @@ enum NoMessageResolver implements MessageResolver {
 	@Nullable
 	@Override
 	public String resolve(MessageSourceResolvable resolvable) {
-		return null;
+		return resolvable.getDefaultMessage();
 	}
 }

src/main/java/org/springframework/hateoas/mediatype/MessageResolver.java

@@ -28,7 +28,7 @@ import org.springframework.lang.Nullable;
  */
 public interface MessageResolver {
 
-	public static final MessageResolver NONE = NoMessageResolver.INSTANCE;
+	public static final MessageResolver DEFAULTS_ONLY = DefaultOnlyMessageResolver.INSTANCE;
 
 	/**
 	 * Resolve the given {@link MessageSourceResolvable}. Return {@literal null} if no message was found.
@@ -46,6 +46,9 @@ public interface MessageResolver {
 	 * @return will never be {@literal null}.
 	 */
 	public static MessageResolver of(@Nullable MessageSource messageSource) {
-		return messageSource == null ? NoMessageResolver.INSTANCE : new MessageSourceResolver(messageSource);
+
+		return messageSource == null //
+				? DefaultOnlyMessageResolver.INSTANCE //
+				: new MessageSourceResolver(messageSource);
 	}
 }

src/main/java/org/springframework/hateoas/mediatype/hal/HalMediaTypeConfiguration.java

@@ -18,6 +18,7 @@ package org.springframework.hateoas.mediatype.hal;
 import java.util.List;
 
 import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.hateoas.client.LinkDiscoverer;
@@ -42,7 +43,7 @@ public class HalMediaTypeConfiguration implements HypermediaMappingInformation {
 	private final LinkRelationProvider relProvider;
 	private final ObjectProvider<CurieProvider> curieProvider;
 	private final ObjectProvider<HalConfiguration> halConfiguration;
-	private final MessageResolver resolver;
+	private final @Qualifier("messageResolver") MessageResolver resolver;
 
 	/**
 	 * @param relProvider

src/main/java/org/springframework/hateoas/mediatype/hal/Jackson2HalModule.java

@@ -121,14 +121,19 @@ public class Jackson2HalModule extends SimpleModule {
 		}
 
 		public HalLinkListSerializer(@Nullable BeanProperty property, CurieProvider curieProvider, EmbeddedMapper mapper,
-				MessageResolver accessor, HalConfiguration halConfiguration) {
+				MessageResolver resolver, HalConfiguration halConfiguration) {
 
 			super(TypeFactory.defaultInstance().constructType(Links.class));
 
+			Assert.notNull(curieProvider, "CurieProvider must not be null!");
+			Assert.notNull(mapper, "EmbeddedMapper must not be null!");
+			Assert.notNull(resolver, "MessageResolver must not be null!");
+			Assert.notNull(halConfiguration, "HalConfiguration must not be null!");
+
 			this.property = property;
 			this.curieProvider = curieProvider;
 			this.mapper = mapper;
-			this.resolver = accessor;
+			this.resolver = resolver;
 			this.halConfiguration = halConfiguration;
 		}
 

src/test/java/org/springframework/hateoas/client/Server.java

@@ -65,7 +65,7 @@ public class Server implements Closeable {
 		this.mapper = new ObjectMapper();
 		this.mapper.registerModule(new Jackson2HalModule());
 		this.mapper.setHandlerInstantiator(
-				new Jackson2HalModule.HalHandlerInstantiator(relProvider, CurieProvider.NONE, MessageResolver.NONE));
+				new Jackson2HalModule.HalHandlerInstantiator(relProvider, CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY));
 
 		initJadler() //
 				.withDefaultResponseContentType(MediaTypes.HAL_JSON.toString()) //

src/test/java/org/springframework/hateoas/config/EnableHypermediaSupportIntegrationTest.java

@@ -16,9 +16,11 @@
 package org.springframework.hateoas.config;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.mockito.Mockito.*;
 import static org.springframework.hateoas.mediatype.hal.HalConfiguration.RenderSingleLinks.*;
 import static org.springframework.hateoas.support.ContextTester.*;
 
+import java.io.IOException;
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Optional;
@@ -26,17 +28,21 @@ import java.util.function.Function;
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mockito;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.RepresentationModel;
 import org.springframework.hateoas.client.LinkDiscoverer;
 import org.springframework.hateoas.client.LinkDiscoverers;
 import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
+import org.springframework.hateoas.mediatype.MessageResolver;
 import org.springframework.hateoas.mediatype.collectionjson.CollectionJsonLinkDiscoverer;
 import org.springframework.hateoas.mediatype.hal.HalConfiguration;
 import org.springframework.hateoas.mediatype.hal.HalLinkDiscoverer;
@@ -54,6 +60,7 @@ import org.springframework.http.converter.json.MappingJackson2HttpMessageConvert
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.web.client.RestTemplate;
+import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.method.support.HandlerMethodArgumentResolverComposite;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
@@ -522,6 +529,37 @@ class EnableHypermediaSupportIntegrationTest {
 		);
 	}
 
+	@Test // #1019
+	void registersNoOpMessageResolverIfMessagesBundleMissing() {
+
+		withServletContext(HateoasConfiguration.class, //
+				context -> {
+					assertThat(context.getBean(MessageResolver.class)).isEqualTo(MessageResolver.of(null));
+				});
+	}
+
+	@Test // #1019
+	void registersMessageResolverIfMessagesBundleAvailable() {
+
+		withServletContext(HateoasConfiguration.class, simulateResourceBundle(), context -> {
+			assertThat(context.getBean(MessageResolver.class)).isNotEqualTo(MessageResolver.of(null));
+		});
+	}
+
+	@Test // #1019, DATAREST-686
+	void defaultsEncodingOfMessageSourceToUtf8() throws Exception {
+
+		withServletContext(HalConfig.class, simulateResourceBundle(), context -> {
+
+			MessageResolver resolver = context.getBean(MessageResolver.class);
+
+			Object accessor = ReflectionTestUtils.getField(resolver, "accessor");
+			Object messageSource = ReflectionTestUtils.getField(accessor, "messageSource");
+
+			assertThat((String) ReflectionTestUtils.getField(messageSource, "defaultEncoding")).isEqualTo("UTF-8");
+		});
+	}
+
 	private static void assertEntityLinksSetUp(ApplicationContext context) {
 
 		assertThat(context.getBeansOfType(EntityLinks.class).values()) //
@@ -607,6 +645,29 @@ class EnableHypermediaSupportIntegrationTest {
 		throw new IllegalStateException("Unexpected result when looking up argument resolvers!");
 	}
 
+	private static <T extends AnnotationConfigWebApplicationContext> Function<T, T> simulateResourceBundle() {
+
+		return context -> {
+
+			T spy = Mockito.spy(context);
+
+			ClassPathResource resource = new ClassPathResource("rest-messages.properties",
+					EnableHypermediaSupportIntegrationTest.class);
+			assertThat(resource.exists()).isTrue();
+
+			try {
+
+				doReturn(new Resource[0]).when(spy).getResources("classpath:rest-default-messages.properties");
+				doReturn(new Resource[] { resource }).when(spy).getResources("classpath:rest-messages*.properties");
+
+			} catch (IOException o_O) {
+				fail("Couldn't mock resource lookup!", o_O);
+			}
+
+			return spy;
+		};
+	}
+
 	@Configuration
 	@EnableWebMvc
 	@Import(DelegateConfig.class)

src/test/java/org/springframework/hateoas/mediatype/hal/Jackson2HalIntegrationTest.java

@@ -89,7 +89,7 @@ public class Jackson2HalIntegrationTest extends AbstractJackson2MarshallingInteg
 
 		mapper.registerModule(new Jackson2HalModule());
 		mapper.setHandlerInstantiator(
-				new HalHandlerInstantiator(provider, CurieProvider.NONE, MessageResolver.NONE, new HalConfiguration()));
+				new HalHandlerInstantiator(provider, CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY, new HalConfiguration()));
 	}
 
 	/**
@@ -447,7 +447,7 @@ public class Jackson2HalIntegrationTest extends AbstractJackson2MarshallingInteg
 	void rendersSingleLinkAsArrayWhenConfigured() throws Exception {
 
 		mapper.setHandlerInstantiator(new HalHandlerInstantiator(new AnnotationLinkRelationProvider(), CurieProvider.NONE,
-				MessageResolver.NONE, new HalConfiguration().withRenderSingleLinks(RenderSingleLinks.AS_ARRAY)));
+				MessageResolver.DEFAULTS_ONLY, new HalConfiguration().withRenderSingleLinks(RenderSingleLinks.AS_ARRAY)));
 
 		RepresentationModel<?> resourceSupport = new RepresentationModel<>();
 		resourceSupport.add(new Link("localhost").withSelfRel());
@@ -480,7 +480,7 @@ public class Jackson2HalIntegrationTest extends AbstractJackson2MarshallingInteg
 
 		AnnotationLinkRelationProvider provider = new AnnotationLinkRelationProvider();
 
-		mapper.setHandlerInstantiator(new HalHandlerInstantiator(provider, CurieProvider.NONE, MessageResolver.NONE,
+		mapper.setHandlerInstantiator(new HalHandlerInstantiator(provider, CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY,
 				new HalConfiguration().withRenderSingleLinksFor("foo", RenderSingleLinks.AS_ARRAY)));
 
 		RepresentationModel<?> resource = new RepresentationModel<>();

src/test/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsMessageConverterUnitTest.java

@@ -56,7 +56,7 @@ class HalFormsMessageConverterUnitTest {
 		this.mapper.registerModule(new Jackson2HalFormsModule());
 		this.mapper.setHandlerInstantiator(
 				new Jackson2HalFormsModule.HalFormsHandlerInstantiator(new AnnotationLinkRelationProvider(), CurieProvider.NONE,
-						MessageResolver.NONE, true, new HalFormsConfiguration()));
+						MessageResolver.DEFAULTS_ONLY, true, new HalFormsConfiguration()));
 
 		TypeConstrainedMappingJackson2HttpMessageConverter converter = new TypeConstrainedMappingJackson2HttpMessageConverter(
 				RepresentationModel.class);

src/test/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsTemplateBuilderUnitTest.java

@@ -45,7 +45,7 @@ public class HalFormsTemplateBuilderUnitTest {
 		HalFormsConfiguration configuration = new HalFormsConfiguration();
 		configuration.registerPattern(CreditCardNumber.class, "[0-9]{16}");
 
-		HalFormsTemplateBuilder builder = new HalFormsTemplateBuilder(configuration, MessageResolver.NONE);
+		HalFormsTemplateBuilder builder = new HalFormsTemplateBuilder(configuration, MessageResolver.DEFAULTS_ONLY);
 
 		PatternExample resource = new PatternExample();
 		resource.add(Affordances.of(new Link("/examples")) //
@@ -79,7 +79,7 @@ public class HalFormsTemplateBuilderUnitTest {
 				.withName("post") //
 				.toLink());
 
-		HalFormsTemplateBuilder builder = new HalFormsTemplateBuilder(new HalFormsConfiguration(), MessageResolver.NONE);
+		HalFormsTemplateBuilder builder = new HalFormsTemplateBuilder(new HalFormsConfiguration(), MessageResolver.DEFAULTS_ONLY);
 
 		Map<String, HalFormsTemplate> templates = builder.findTemplates(model);
 

src/test/java/org/springframework/hateoas/mediatype/hal/forms/Jackson2HalFormsIntegrationTest.java

@@ -94,7 +94,7 @@ class Jackson2HalFormsIntegrationTest extends AbstractJackson2MarshallingIntegra
 
 		mapper.registerModule(new Jackson2HalFormsModule());
 		mapper.setHandlerInstantiator(new HalFormsHandlerInstantiator( //
-				provider, CurieProvider.NONE, MessageResolver.NONE, true, new HalFormsConfiguration()));
+				provider, CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY, true, new HalFormsConfiguration()));
 		mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
 	}
 

src/test/java/org/springframework/hateoas/mediatype/vnderror/VndErrorsMarshallingTest.java

@@ -66,7 +66,7 @@ class VndErrorsMarshallingTest {
 		jackson2Mapper = new com.fasterxml.jackson.databind.ObjectMapper();
 		jackson2Mapper.registerModule(new Jackson2HalModule());
 		jackson2Mapper.setHandlerInstantiator(
-				new Jackson2HalModule.HalHandlerInstantiator(relProvider, CurieProvider.NONE, MessageResolver.NONE));
+				new Jackson2HalModule.HalHandlerInstantiator(relProvider, CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY));
 		jackson2Mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
 
 		VndError error = new VndError("42", "Validation failed!", //

src/test/java/org/springframework/hateoas/support/ContextTester.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.hateoas.support;
 
+import java.util.function.Function;
+
 import org.springframework.mock.web.MockServletContext;
 import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
 
@@ -24,7 +26,7 @@ import org.springframework.web.context.support.AnnotationConfigWebApplicationCon
 public class ContextTester {
 
 	public static <E extends Exception> void withContext(Class<?> configuration,
-		 	ConsumerWithException<AnnotationConfigWebApplicationContext, E> consumer) throws E {
+			ConsumerWithException<AnnotationConfigWebApplicationContext, E> consumer) throws E {
 
 		try (AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext()) {
 
@@ -36,18 +38,26 @@ public class ContextTester {
 	}
 
 	public static <E extends Exception> void withServletContext(Class<?> configuration,
-			  ConsumerWithException<AnnotationConfigWebApplicationContext, E> consumer) throws E {
+			ConsumerWithException<AnnotationConfigWebApplicationContext, E> consumer) throws E {
 
-		try (AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext()) {
+		withServletContext(configuration, Function.identity(), consumer);
+	}
 
-			context.register(configuration);
-			context.setServletContext(new MockServletContext());
-			context.refresh();
+	public static <E extends Exception> void withServletContext(Class<?> configuration,
+			Function<AnnotationConfigWebApplicationContext, AnnotationConfigWebApplicationContext> preparer,
+			ConsumerWithException<AnnotationConfigWebApplicationContext, E> consumer) throws E {
 
-			consumer.accept(context);
+		AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
+		context.register(configuration);
+		context.setServletContext(new MockServletContext());
+
+		try (AnnotationConfigWebApplicationContext prepared = preparer.apply(context)) {
+
+			prepared.refresh();
+			consumer.accept(prepared);
 		}
 	}
-	
+
 	public interface ConsumerWithException<T, E extends Exception> {
 
 		void accept(T element) throws E;