Introduce SynchronizedItemStreamWriter

Issue #842

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;
+	}
+}