Add a builder for the JpaItemWriter

Resolves BATCH-2714.

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/database/builder/JpaItemWriterBuilder.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.batch.item.database.builder;
+
+import javax.persistence.EntityManagerFactory;
+
+import org.springframework.batch.item.database.JpaItemWriter;
+import org.springframework.util.Assert;
+
+/**
+ * A builder for the {@link JpaItemWriter}.
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ * @see JpaItemWriter
+ */
+public class JpaItemWriterBuilder<T> {
+
+	private EntityManagerFactory entityManagerFactory;
+
+	/**
+	 * The JPA {@link EntityManagerFactory} to obtain an entity manager from. Required.
+	 *
+	 * @param entityManagerFactory the {@link EntityManagerFactory}
+	 * @return this instance for method chaining
+	 * @see JpaItemWriter#setEntityManagerFactory(EntityManagerFactory)
+	 */
+	public JpaItemWriterBuilder<T> entityManagerFactory(EntityManagerFactory entityManagerFactory) {
+		this.entityManagerFactory = entityManagerFactory;
+
+		return this;
+	}
+
+	/**
+	 * Returns a fully built {@link JpaItemWriter}.
+	 *
+	 * @return the writer
+	 */
+	public JpaItemWriter<T> build() {
+		Assert.state(this.entityManagerFactory != null,
+				"EntityManagerFactory must be provided");
+
+		JpaItemWriter<T> writer = new JpaItemWriter<>();
+		writer.setEntityManagerFactory(this.entityManagerFactory);
+
+		return writer;
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/database/builder/JpaItemWriterBuilderTests.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.batch.item.database.builder;
+
+import java.util.Arrays;
+import java.util.List;
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import org.springframework.batch.item.database.JpaItemWriter;
+import org.springframework.orm.jpa.EntityManagerHolder;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+import static org.mockito.Mockito.verify;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class JpaItemWriterBuilderTests {
+
+	@Mock
+	private EntityManagerFactory entityManagerFactory;
+
+	@Mock
+	private EntityManager entityManager;
+
+	@Before
+	public void setUp() {
+		MockitoAnnotations.initMocks(this);
+		TransactionSynchronizationManager.bindResource(this.entityManagerFactory,
+				new EntityManagerHolder(this.entityManager));
+	}
+
+	@After
+	public void tearDown() {
+		TransactionSynchronizationManager.unbindResource(this.entityManagerFactory);
+	}
+
+	@Test
+	public void testConfiguration() throws Exception {
+		JpaItemWriter<String> itemWriter = new JpaItemWriterBuilder<String>()
+				.entityManagerFactory(this.entityManagerFactory)
+				.build();
+
+		itemWriter.afterPropertiesSet();
+
+		List<String> items = Arrays.asList("foo", "bar");
+
+		itemWriter.write(items);
+
+		verify(this.entityManager).merge(items.get(0));
+		verify(this.entityManager).merge(items.get(1));
+	}
+
+	@Test
+	public void testValidation() {
+		try {
+			new JpaItemWriterBuilder<String>()
+					.build();
+			fail("Should fail if no EntityManagerFactory is provided");
+		}
+		catch (IllegalStateException ise) {
+			assertEquals("Incorrect message", "EntityManagerFactory must be provided", ise.getMessage());
+		}
+	}
+}