From 4a36bf08cb1e89f361eecd05cc194bf2f96b6125 Mon Sep 17 00:00:00 2001
From: Mark Fisher <markfisher@vmware.com>
Date: Mon, 3 Dec 2007 00:43:35 +0000
Subject: [PATCH] Added message source adapters for polling sources.

---
 .../AbstractPollingMessageSource.java         | 66 ++++++++++++++++++
 .../AbstractPrefetchingMessageSource.java     | 68 +++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPollingMessageSource.java
 create mode 100644 spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPrefetchingMessageSource.java

diff --git a/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPollingMessageSource.java b/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPollingMessageSource.java
new file mode 100644
index 0000000000..66c19ada67
--- /dev/null
+++ b/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPollingMessageSource.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2002-2007 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.integration.endpoint;
+
+import org.springframework.integration.MessageSource;
+import org.springframework.integration.message.Message;
+import org.springframework.integration.message.MessageMapper;
+import org.springframework.integration.message.SimplePayloadMessageMapper;
+import org.springframework.util.Assert;
+
+/**
+ * A {@link MessageSource} adapter for any source that can be polled for
+ * objects.
+ * 
+ * @author Mark Fisher
+ */
+public abstract class AbstractPollingMessageSource implements MessageSource {
+
+	private MessageMapper mapper = new SimplePayloadMessageMapper();
+
+
+	public void setMapper(MessageMapper mapper) {
+		Assert.notNull(mapper, "mapper must not be null");
+		this.mapper = mapper;
+	}
+
+	public Message receive() {
+		return this.receive(-1);
+	}
+
+	public Message receive(long timeout) {
+		long start = System.currentTimeMillis();
+		while (timeout <= 0 || System.currentTimeMillis() - start < timeout) {
+			Object o = this.pollForObject();
+			if (o != null) {
+				return this.mapper.toMessage(o);
+			}
+			if (timeout == 0) {
+				return null;
+			}
+		}
+		return null;
+	}
+
+
+	/**
+	 * Method for subclasses to implement. Returns an object to be mapped to a
+	 * {@link Message} by the message mapper.
+	 */
+	protected abstract Object pollForObject();
+
+}
diff --git a/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPrefetchingMessageSource.java b/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPrefetchingMessageSource.java
new file mode 100644
index 0000000000..f8b157358b
--- /dev/null
+++ b/spring-eai-core/src/main/java/org/springframework/integration/endpoint/AbstractPrefetchingMessageSource.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2002-2007 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.integration.endpoint;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.springframework.integration.MessageSource;
+import org.springframework.integration.message.Message;
+
+/**
+ * A {@link MessageSource} adapter for any source that can be polled for
+ * objects. This version allows for pre-fetching multiple results so that
+ * subsequent calls to {@link #pollForObject()} may be more efficient.
+ * 
+ * @author Mark Fisher
+ */
+public abstract class AbstractPrefetchingMessageSource extends AbstractPollingMessageSource {
+
+	private BlockingQueue<Object> queue = new LinkedBlockingQueue<Object>();
+
+
+	public Object pollForObject() {
+		Object o = queue.poll();
+		if (o == null) {
+			this.prefetch();
+			o = queue.poll();
+		}
+		return o;
+	}
+
+	private void prefetch() {
+		Object[] results = this.pollForObjects();
+		if (results != null) {
+			try {
+				for (Object o : results) {
+					queue.put(o);
+				}
+			}
+			catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+				return;
+			}
+		}
+	}
+
+
+	/**
+	 * Method for subclasses to implement. Returns objects to be mapped to
+	 * {@link Message Messages} by the message mapper.
+	 */
+	protected abstract Object[] pollForObjects();
+
+}