DATAREDIS-1049 - Fix retrieval of empty keyspaceNotificationsConfigParameter used to keep server defaults.

Empty Strings changed to be considered null throwing an exception on getRequiredAttribute so we now set the value explicitly for this attribute when considered empty. Original pull request: spring-projects#491.

Author: christophstrobl

src/main/java/org/springframework/data/redis/repository/configuration/EnableRedisRepositories.java

@@ -168,7 +168,7 @@
 
 /**
  * Configure the {@literal notify-keyspace-events} property if not already set. <br />
- * Use an empty {@link String} to keep <b>not</b> alter existing server configuration.
+ * Use an empty {@link String} to keep (<b>not</b> alter) existing server configuration.
  *
  * @return {@literal Ex} by default.
  * @since 1.8

src/main/java/org/springframework/data/redis/repository/configuration/RedisRepositoryConfigurationExtension.java

@@ -144,7 +144,7 @@ private static AbstractBeanDefinition createRedisKeyValueAdapter(RepositoryConfi
 .addPropertyValue("enableKeyspaceEvents",
 configuration.getRequiredAttribute("enableKeyspaceEvents", EnableKeyspaceEvents.class)) //
 .addPropertyValue("keyspaceNotificationsConfigParameter",
-configuration.getRequiredAttribute("keyspaceNotificationsConfigParameter", String.class)) //
+configuration.getAttribute("keyspaceNotificationsConfigParameter", String.class).orElse("")) //
 .getBeanDefinition();
 }
 

src/test/java/org/springframework/data/redis/repository/configuration/RedisRepositoryConfigurationExtensionUnitTests.java

@@ -114,6 +114,15 @@ public void picksUpCustomKeyspaceNotificationsConfigParameterCorrectly() {
 assertThat(getKeyspaceNotificationsConfigParameter(beanDefintionRegistry)).isEqualTo((Object) "KEA");
 }
 
+@Test // DATAREDIS-1049
+public void explicitlyEmptyKeyspaceNotificationsConfigParameterShouldBeCapturedCorrectly() {
+
+metadata = new StandardAnnotationMetadata(ConfigWithEmptyConfigParameter.class, true);
+BeanDefinitionRegistry beanDefintionRegistry = getBeanDefinitionRegistry();
+
+assertThat(getKeyspaceNotificationsConfigParameter(beanDefintionRegistry)).isEqualTo("");
+}
+
 private static void assertDoesNotHaveRepo(Class<?> repositoryInterface,
 Collection<RepositoryConfiguration<RepositoryConfigurationSource>> configs) {
 
@@ -179,6 +188,12 @@ static class ConfigWithKeyspaceEventsEnabledAndCustomEventConfig {
 
 }
 
+@EnableRedisRepositories(considerNestedRepositories = true, enableKeyspaceEvents = EnableKeyspaceEvents.ON_STARTUP,
+keyspaceNotificationsConfigParameter = "")
+static class ConfigWithEmptyConfigParameter {
+
+}
+
 @RedisHash
 static class Sample {
 @Id String id;