Refine contribution #4521

- Update reference documentation
- Minor test updates

(cherry picked from commit d6b6361e59)

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/JobRegistrySmartInitializingSingleton.java

@@ -113,8 +113,8 @@ public class JobRegistrySmartInitializingSingleton
 	}
 
 	/**
-	 * Unregister all the {@link Job} instances that were registered by this post
-	 * processor.
+	 * Unregister all the {@link Job} instances that were registered by this smart
+	 * initializing singleton.
 	 */
 	@Override
 	public void destroy() throws Exception {

spring-batch-core/src/test/java/org/springframework/batch/core/configuration/support/JobRegistrySmartInitializingSingletonTests.java

@@ -29,6 +29,7 @@ import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -37,6 +38,7 @@ import static org.mockito.Mockito.mock;
 
 /**
  * @author Henning Pöttker
+ * @author Mahmoud Ben Hassine
  */
 class JobRegistrySmartInitializingSingletonTests {
 
@@ -59,34 +61,38 @@ class JobRegistrySmartInitializingSingletonTests {
 	void testInitializationFails() {
 		singleton.setJobRegistry(null);
 		var exception = assertThrows(IllegalStateException.class, singleton::afterPropertiesSet);
-		assertTrue(exception.getMessage().contains("JobRegistry"));
+		assertEquals("JobRegistry must not be null", exception.getMessage());
 	}
 
 	@Test
 	void testAfterSingletonsInstantiated() {
 		singleton.afterSingletonsInstantiated();
-		assertEquals("[foo]", jobRegistry.getJobNames().toString());
+		Collection<String> jobNames = jobRegistry.getJobNames();
+		assertEquals(1, jobNames.size());
+		assertEquals("foo", jobNames.iterator().next());
 	}
 
 	@Test
 	void testAfterSingletonsInstantiatedWithGroupName() {
 		singleton.setGroupName("jobs");
 		singleton.afterSingletonsInstantiated();
-		assertEquals("[jobs.foo]", jobRegistry.getJobNames().toString());
+		Collection<String> jobNames = jobRegistry.getJobNames();
+		assertEquals(1, jobNames.size());
+		assertEquals("jobs.foo", jobNames.iterator().next());
 	}
 
 	@Test
 	void testAfterSingletonsInstantiatedWithDuplicate() {
 		singleton.afterSingletonsInstantiated();
 		var exception = assertThrows(FatalBeanException.class, singleton::afterSingletonsInstantiated);
-		assertTrue(exception.getCause() instanceof DuplicateJobException);
+		assertInstanceOf(DuplicateJobException.class, exception.getCause());
 	}
 
 	@Test
 	void testUnregisterOnDestroy() throws Exception {
 		singleton.afterSingletonsInstantiated();
 		singleton.destroy();
-		assertEquals("[]", jobRegistry.getJobNames().toString());
+		assertTrue(jobRegistry.getJobNames().isEmpty());
 	}
 
 	@Test

spring-batch-docs/modules/ROOT/pages/job/advanced-meta-data.adoc

@@ -173,9 +173,9 @@ The following example shows how to include a `JobRegistry` for a job defined in
 
 ====
 
-You can populate a `JobRegistry` in either of two ways: by using
-a bean post processor or by using a registrar lifecycle component. The coming
-sections describe these two mechanisms.
+You can populate a `JobRegistry` in one of the following ways: by using
+a bean post processor, or by using a smart initializing singleton or by using
+a registrar lifecycle component. The coming sections describe these mechanisms.
 
 [[jobregistrybeanpostprocessor]]
 === JobRegistryBeanPostProcessor
@@ -224,6 +224,40 @@ there to also be registered automatically.
 
 As of version 5.1, the `@EnableBatchProcessing` annotation automatically registers a `jobRegistryBeanPostProcessor` bean in the application context.
 
+[[jobregistrysmartinitializingsingleton]]
+=== JobRegistrySmartInitializingSingleton
+
+This is a `SmartInitializingSingleton` that registers all singleton jobs within the job registry.
+
+[tabs]
+====
+Java::
++
+The following example shows how to define a `JobRegistrySmartInitializingSingleton` in Java:
++
+.Java Configuration
+[source, java]
+----
+@Bean
+public JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton(JobRegistry jobRegistry) {
+    return new JobRegistrySmartInitializingSingleton(jobRegistry);
+}
+----
+
+XML::
++
+The following example shows how to define a `JobRegistrySmartInitializingSingleton` in XML:
++
+.XML Configuration
+[source, xml]
+----
+<bean class="org.springframework.batch.core.configuration.support.JobRegistrySmartInitializingSingleton">
+    <property name="jobRegistry" ref="jobRegistry" />
+</bean>
+----
+
+====
+
 [[automaticjobregistrar]]
 === AutomaticJobRegistrar