Add GemFire Support

Fixes GH PR #148 and PR #308 implementing a GemFire Adapter to support
clustered HttpSessions in Spring Session.

* Resolve SGF-373 - Implement a Spring Session Adapter for GemFire backing
a HttpSession similar to the Redis support.
* Add Spring Session annotation to enable GemFire support with
@EnableGemFireHttpSession.
* Add extesion of SpringHttpSessionConfiguration to configure GemFire using
GemFireHttpSessionConfiguration.
* Add implementation of SessionRepository to access clustered, replicated
HttpSession state in GemFire with GemFireOperationsSessionRepository.
* Utilize GemFire Data Serialization framework to both replicate
HttpSession state information as well as handle deltas.
* Utilize GemFire OQL query to lookup arbitrary Session attributes by name,
and in particular the user authenticated principal name.
* Implment unit and integration tests, and in particular, tests for both
peer-to-peer (p2p) and client/server topologies.
* Set initial Spring Data GemFire version to 1.7.2.RELEASE, which depends
on Pivotal GemFire 8.1.0.
* Add documentation, Javadoc and samples along with additional Integration
Tests.

Fixes gh-148

samples/httpsession-gemfire-clientserver-xml/src/main/java/sample/Application.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2002-2015 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 sample;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.ImportResource;
+
+// tag::class[]
+@Configuration // <1>
+@ImportResource("META-INF/spring/session-server.xml") // <2>
+public class Application {
+
+	public static void main(final String[] args) {
+		new AnnotationConfigApplicationContext(Application.class).registerShutdownHook();
+	}
+}
+// tag::end[]

samples/httpsession-gemfire-clientserver-xml/src/main/java/sample/GemFireCacheServerReadyBeanPostProcessor.java

@@ -0,0 +1,151 @@
+/*
+ * Copyright 2002-2015 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 sample;
+
+import java.io.IOException;
+import java.net.Socket;
+import java.util.Properties;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import javax.annotation.Resource;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.data.gemfire.client.PoolFactoryBean;
+import org.springframework.session.data.gemfire.support.GemFireUtils;
+import org.springframework.util.Assert;
+
+import com.gemstone.gemfire.cache.client.Pool;
+import com.gemstone.gemfire.management.membership.ClientMembership;
+import com.gemstone.gemfire.management.membership.ClientMembershipEvent;
+import com.gemstone.gemfire.management.membership.ClientMembershipListenerAdapter;
+
+public class GemFireCacheServerReadyBeanPostProcessor implements BeanPostProcessor {
+
+	static final long DEFAULT_WAIT_DURATION = TimeUnit.SECONDS.toMillis(20);
+	static final long DEFAULT_WAIT_INTERVAL = 500l;
+
+	static final CountDownLatch latch = new CountDownLatch(1);
+
+	static final String DEFAULT_SERVER_HOST = "localhost";
+
+	@Value("${spring.session.data.gemfire.port:${application.gemfire.client-server.port}}")
+	int port;
+
+// tag::class[]
+	static {
+		ClientMembership.registerClientMembershipListener(new ClientMembershipListenerAdapter() {
+			public void memberJoined(final ClientMembershipEvent event) {
+				if (!event.isClient()) {
+					latch.countDown();
+				}
+			}
+		});
+	}
+
+	@SuppressWarnings("all")
+	@Resource(name = "applicationProperties")
+	private Properties applicationProperties;
+
+	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
+		if (bean instanceof PoolFactoryBean || bean instanceof Pool) {
+			String host = getServerHost(DEFAULT_SERVER_HOST);
+			Assert.isTrue(waitForCacheServerToStart(host, port), String.format(
+				"GemFire Server failed to start [host: '%1$s', port: %2$d]%n", host, port));
+		}
+
+		return bean;
+	}
+
+	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+		if (bean instanceof PoolFactoryBean || bean instanceof Pool) {
+			try {
+				latch.await(DEFAULT_WAIT_DURATION, TimeUnit.MILLISECONDS);
+			}
+			catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+			}
+		}
+
+		return bean;
+	}
+// tag::end[]
+
+	interface Condition {
+		boolean evaluate();
+	}
+
+	String getServerHost(String defaultServerHost) {
+		return applicationProperties.getProperty("application.gemfire.client-server.host", defaultServerHost);
+	}
+
+	boolean waitForCacheServerToStart(String host, int port) {
+		return waitForCacheServerToStart(host, port, DEFAULT_WAIT_DURATION);
+	}
+
+	/* (non-Javadoc) */
+	boolean waitForCacheServerToStart(final String host, final int port, long duration) {
+		return waitOnCondition(new Condition() {
+			AtomicBoolean connected = new AtomicBoolean(false);
+
+			public boolean evaluate() {
+				Socket socket = null;
+
+				try {
+					// NOTE: this code is not intended to be an atomic, compound action (a possible race condition);
+					// opening another connection (at the expense of using system resources) after connectivity
+					// has already been established is not detrimental in this use case
+					if (!connected.get()) {
+						socket = new Socket(host, port);
+						connected.set(true);
+					}
+				}
+				catch (IOException ignore) {
+				}
+				finally {
+					GemFireUtils.close(socket);
+				}
+
+				return connected.get();
+			}
+		}, duration);
+	}
+
+	@SuppressWarnings("unused")
+	boolean waitOnCondition(Condition condition) {
+		return waitOnCondition(condition, DEFAULT_WAIT_DURATION);
+	}
+
+	@SuppressWarnings("all")
+	boolean waitOnCondition(Condition condition, long duration) {
+		final long timeout = (System.currentTimeMillis() + duration);
+
+		try {
+			while (!condition.evaluate() && System.currentTimeMillis() < timeout) {
+				synchronized (condition) {
+					TimeUnit.MILLISECONDS.timedWait(condition, DEFAULT_WAIT_INTERVAL);
+				}
+			}
+		}
+		catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+		}
+
+		return condition.evaluate();
+	}
+}

samples/httpsession-gemfire-clientserver-xml/src/main/java/sample/SessionServlet.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2002-2015 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 sample;
+
+import java.io.IOException;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+// tag::class[]
+public class SessionServlet extends HttpServlet {
+
+	@Override
+	protected void doPost(HttpServletRequest request, HttpServletResponse response)
+			throws ServletException, IOException {
+		String attributeName = request.getParameter("attributeName");
+		String attributeValue = request.getParameter("attributeValue");
+		request.getSession().setAttribute(attributeName, attributeValue);
+		response.sendRedirect(request.getContextPath() + "/");
+	}
+
+	private static final long serialVersionUID = 2878267318695777395L;
+}
+// tag::end[]