Introduce SynchronizedItemStreamWriter

Issue #842

spring-batch-docs/asciidoc/readersAndWriters.adoc

@@ -3000,6 +3000,7 @@ Spring Batch includes the following decorators:
 
 * <<synchronizedItemStreamReader>>
 * <<singleItemPeekableItemReader>>
+* <<synchronizedItemStreamWriter>>
 * <<multiResourceItemWriter>>
 * <<classifierCompositeItemWriter>>
 * <<classifierCompositeItemProcessor>>
@@ -3023,6 +3024,13 @@ NOTE: SingleItemPeekableItemReader's peek method is not thread-safe, because it
 be possible to honor the peek in multiple threads. Only one of the threads that peeked
 would get that item in the next call to read.
 
+[[synchronizedItemStreamWriter]]
+===== `SynchronizedItemStreamWriter`
+When using an `ItemWriter` that is not thread safe, Spring Batch offers the
+`SynchronizedItemStreamWriter` decorator, which can be used to make the `ItemWriter`
+thread safe. Spring Batch provides a `SynchronizedItemStreamWriterBuilder` to construct
+an instance of the `SynchronizedItemStreamWriter`.
+
 [[multiResourceItemWriter]]
 ===== `MultiResourceItemWriter`
 The `MultiResourceItemWriter` wraps a `ResourceAwareItemWriterItemStream` and creates a new

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/SynchronizedItemStreamWriter.java

@@ -0,0 +1,69 @@
+/*
+ * 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.support;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.batch.item.ItemStreamWriter;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+import java.util.List;
+
+/**
+ * An {@link ItemStreamWriter} decorator with a synchronized
+ * {@link SynchronizedItemStreamWriter#write write()} method
+ *
+ * @author Dimitrios Liapis
+ *
+ * @param <T> type of object being written
+ */
+public class SynchronizedItemStreamWriter<T> implements ItemStreamWriter<T>, InitializingBean {
+
+	private ItemStreamWriter<T> delegate;
+
+	public void setDelegate(ItemStreamWriter<T> delegate) {
+		this.delegate = delegate;
+	}
+
+	/**
+	 * This delegates to the write method of the <code>delegate</code>
+	 */
+	@Override
+	public synchronized void write(List<? extends T> items) throws Exception {
+		this.delegate.write(items);
+	}
+
+	@Override
+	public void open(ExecutionContext executionContext) throws ItemStreamException {
+		this.delegate.open(executionContext);
+	}
+
+	@Override
+	public void update(ExecutionContext executionContext) throws ItemStreamException {
+		this.delegate.update(executionContext);
+	}
+
+	@Override
+	public void close() throws ItemStreamException {
+		this.delegate.close();
+	}
+
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		Assert.notNull(this.delegate, "A delegate item writer is required");
+	}
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/builder/SynchronizedItemStreamWriterBuilder.java

@@ -0,0 +1,44 @@
+/*
+ * 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.support.builder;
+
+import org.springframework.batch.item.ItemStreamWriter;
+import org.springframework.batch.item.support.SynchronizedItemStreamWriter;
+import org.springframework.util.Assert;
+
+/**
+ * Creates a fully qualified {@link SynchronizedItemStreamWriter}.
+ *
+ * @author Dimitrios Liapis
+ */
+public class SynchronizedItemStreamWriterBuilder<T> {
+
+	private ItemStreamWriter<T> delegate;
+
+	public SynchronizedItemStreamWriterBuilder<T> delegate(ItemStreamWriter<T> delegate) {
+		this.delegate = delegate;
+
+		return this;
+	}
+
+	public SynchronizedItemStreamWriter<T> build() {
+		Assert.notNull(this.delegate, "A delegate is required");
+
+		SynchronizedItemStreamWriter<T> writer = new SynchronizedItemStreamWriter<>();
+		writer.setDelegate(this.delegate);
+		return writer;
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/support/AbstractSynchronizedItemStreamWriterTests.java

@@ -0,0 +1,84 @@
+/*
+ * 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.support;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mock;
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamWriter;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static org.mockito.Mockito.verify;
+import static org.mockito.MockitoAnnotations.initMocks;
+
+/**
+ * Common parent class for {@link SynchronizedItemStreamWriterTests} and
+ * {@link org.springframework.batch.item.support.builder.SynchronizedItemStreamWriterBuilderTests}
+ *
+ * @author Dimitrios Liapis
+ *
+ */
+public abstract class AbstractSynchronizedItemStreamWriterTests {
+
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
+
+	@Mock
+	protected ItemStreamWriter<Object> delegate;
+
+	private SynchronizedItemStreamWriter<Object> synchronizedItemStreamWriter;
+	private final List<Object> testList = Collections.unmodifiableList(new ArrayList<>());
+	private final ExecutionContext testExecutionContext = new ExecutionContext();
+
+	abstract protected SynchronizedItemStreamWriter<Object> createNewSynchronizedItemStreamWriter();
+
+	@Before
+	public void init() {
+		initMocks(this);
+		synchronizedItemStreamWriter = createNewSynchronizedItemStreamWriter();
+	}
+
+	@Test
+	public void testDelegateWriteIsCalled() throws Exception {
+		synchronizedItemStreamWriter.write(testList);
+		verify(delegate).write(testList);
+	}
+
+	@Test
+	public void testDelegateOpenIsCalled() {
+		synchronizedItemStreamWriter.open(testExecutionContext);
+		verify(delegate).open(testExecutionContext);
+	}
+
+	@Test
+	public void testDelegateUpdateIsCalled() {
+		synchronizedItemStreamWriter.update(testExecutionContext);
+		verify(delegate).update(testExecutionContext);
+	}
+
+	@Test
+	public void testDelegateCloseIsClosed() {
+		synchronizedItemStreamWriter.close();
+		verify(delegate).close();
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/support/SynchronizedItemStreamWriterTests.java

@@ -0,0 +1,42 @@
+/*
+ * 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.support;
+
+import org.junit.Test;
+import org.springframework.beans.factory.InitializingBean;
+
+/**
+ *
+ * @author Dimitrios Liapis
+ *
+ */
+public class SynchronizedItemStreamWriterTests extends AbstractSynchronizedItemStreamWriterTests {
+
+
+	@Override
+	protected SynchronizedItemStreamWriter<Object> createNewSynchronizedItemStreamWriter() {
+		SynchronizedItemStreamWriter<Object> synchronizedItemStreamWriter = new SynchronizedItemStreamWriter<>();
+		synchronizedItemStreamWriter.setDelegate(delegate);
+		return synchronizedItemStreamWriter;
+	}
+
+	@Test
+	public void testDelegateIsNotNullWhenPropertiesSet() throws Exception {
+		expectedException.expect(IllegalArgumentException.class);
+		expectedException.expectMessage("A delegate item writer is required");
+		((InitializingBean) new SynchronizedItemStreamWriter<>()).afterPropertiesSet();
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/support/builder/SynchronizedItemStreamWriterBuilderTests.java

@@ -0,0 +1,43 @@
+/*
+ * 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.support.builder;
+
+import org.junit.Test;
+import org.springframework.batch.item.support.AbstractSynchronizedItemStreamWriterTests;
+import org.springframework.batch.item.support.SynchronizedItemStreamWriter;
+
+/**
+ *
+ * @author Dimitrios Liapis
+ *
+ */
+public class SynchronizedItemStreamWriterBuilderTests extends AbstractSynchronizedItemStreamWriterTests {
+
+
+	@Override
+	protected SynchronizedItemStreamWriter<Object> createNewSynchronizedItemStreamWriter() {
+		return new SynchronizedItemStreamWriterBuilder<>()
+				.delegate(delegate)
+				.build();
+	}
+
+	@Test
+	public void testBuilderDelegateIsNotNull() {
+		expectedException.expect(IllegalArgumentException.class);
+		expectedException.expectMessage("A delegate is required");
+		new SynchronizedItemStreamWriterBuilder<>().build();
+	}
+}