Remove the lazy proxy creation of batch artifacts in batch configuration

The lazy proxy creation of batch artifacts was intended to prevent
configuration cycles from happening. However, this is implemented in
SimpleBatchConfiguration but not in ModularBatchConfiguration.

Removing this laziness in the configuration process does not introduce
any regression neither in tests nor in samples. This commit makes
SimpleBatchConfiguration consistent with ModularBatchConfiguration.

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/annotation/SimpleBatchConfiguration.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.batch.core.configuration.annotation;
 
+import java.util.Collection;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.aopalliance.intercept.MethodInterceptor;
@@ -34,11 +35,8 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.transaction.PlatformTransactionManager;
 
 /**
- * Base {@code Configuration} class providing common structure for enabling and using Spring Batch. Customization is
- * available by implementing the {@link BatchConfigurer} interface. The main components are created as lazy proxies that
- * only initialize when a method is called. This is to prevent (as much as possible) configuration cycles from
- * developing when these components are needed in a configuration resource that itself provides a
- * {@link BatchConfigurer}.
+ * Base {@code Configuration} class providing common structure for enabling and using Spring Batch.
+ * Customization is available by implementing the {@link BatchConfigurer} interface.
  *
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
@@ -51,98 +49,36 @@ public class SimpleBatchConfiguration extends AbstractBatchConfiguration {
 	@Autowired
 	private ApplicationContext context;
 
-	private boolean initialized = false;
-
-	private AtomicReference<JobRepository> jobRepository = new AtomicReference<>();
-
-	private AtomicReference<JobLauncher> jobLauncher = new AtomicReference<>();
-
-	private AtomicReference<JobRegistry> jobRegistry = new AtomicReference<>();
-
-	private AtomicReference<PlatformTransactionManager> transactionManager = new AtomicReference<>();
-
-	private AtomicReference<JobExplorer> jobExplorer = new AtomicReference<>();
+	@Autowired(required = false)
+	private Collection<BatchConfigurer> configurers;
 
 	@Override
 	@Bean
 	public JobRepository jobRepository() throws Exception {
-		return createLazyProxy(jobRepository, JobRepository.class);
+		return getConfigurer(configurers).getJobRepository();
 	}
 
 	@Override
 	@Bean
 	public JobLauncher jobLauncher() throws Exception {
-		return createLazyProxy(jobLauncher, JobLauncher.class);
+		return getConfigurer(configurers).getJobLauncher();
 	}
 
 	@Override
 	@Bean
 	public JobRegistry jobRegistry() throws Exception {
-		return createLazyProxy(jobRegistry, JobRegistry.class);
+		return new MapJobRegistry();
 	}
 
 	@Override
 	@Bean
-	public JobExplorer jobExplorer() {
-		return createLazyProxy(jobExplorer, JobExplorer.class);
+	public JobExplorer jobExplorer() throws Exception {
+		return getConfigurer(configurers).getJobExplorer();
 	}
 
 	@Override
 	public PlatformTransactionManager transactionManager() throws Exception {
-		return createLazyProxy(transactionManager, PlatformTransactionManager.class);
-	}
-
-	private <T> T createLazyProxy(AtomicReference<T> reference, Class<T> type) {
-		ProxyFactory factory = new ProxyFactory();
-		factory.setTargetSource(new ReferenceTargetSource<>(reference));
-		factory.addAdvice(new PassthruAdvice());
-		factory.setInterfaces(new Class<?>[] { type });
-		@SuppressWarnings("unchecked")
-		T proxy = (T) factory.getProxy();
-		return proxy;
-	}
-
-	/**
-	 * Sets up the basic components by extracting them from the {@link BatchConfigurer configurer}, defaulting to some
-	 * sensible values as long as a unique DataSource is available.
-	 *
-	 * @throws Exception if there is a problem in the configurer
-	 */
-	protected void initialize() throws Exception {
-		if (initialized) {
-			return;
-		}
-		BatchConfigurer configurer = getConfigurer(context.getBeansOfType(BatchConfigurer.class).values());
-		jobRepository.set(configurer.getJobRepository());
-		jobLauncher.set(configurer.getJobLauncher());
-		transactionManager.set(configurer.getTransactionManager());
-		jobRegistry.set(new MapJobRegistry());
-		jobExplorer.set(configurer.getJobExplorer());
-		initialized = true;
-	}
-
-	private class PassthruAdvice implements MethodInterceptor {
-
-		@Override
-		public Object invoke(MethodInvocation invocation) throws Throwable {
-			return invocation.proceed();
-		}
-
-	}
-
-	private class ReferenceTargetSource<T> extends AbstractLazyCreationTargetSource {
-
-		private AtomicReference<T> reference;
-
-		public ReferenceTargetSource(AtomicReference<T> reference) {
-			this.reference = reference;
-		}
-
-		@Override
-		protected Object createObject() throws Exception {
-			initialize();
-			return reference.get();
-		}
+		return getConfigurer(configurers).getTransactionManager();
 	}
 
 }