DATACASS-253 - Add synchronization to CachedPreparedStatementCreator.

CachedPreparedStatementCreator is now thread-safe and synchronizes concurrent calls to statement preparation. The synchronization prevents multiple calls to Session.prepare(…) for the same session, CQL statement and keyspace.

spring-cql/src/test/java/org/springframework/cassandra/core/CachedPreparedStatementCreatorUnitTests.java

@@ -0,0 +1,187 @@
+/*
+ * Copyright 2016 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.cassandra.core;
+
+import static edu.umd.cs.mtc.TestFramework.*;
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.*;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+
+import com.datastax.driver.core.PreparedStatement;
+import com.datastax.driver.core.Session;
+
+import edu.umd.cs.mtc.MultithreadedTestCase;
+
+/**
+ * Unit tests for {@link CachedPreparedStatementCreator}.
+ * 
+ * @author Mark Paluch
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class CachedPreparedStatementCreatorUnitTests {
+
+	PreparedStatement preparedStatement;
+	@Mock Session sessionMock;
+
+	@Before
+	public void before() throws Exception {
+
+		preparedStatement = newProxy(PreparedStatement.class, new TestInvocationHandler());
+		when(sessionMock.prepare(anyString())).thenReturn(preparedStatement);
+	}
+
+	/**
+	 * @see DATACASS-253
+	 */
+	@Test(expected = IllegalArgumentException.class)
+	public void shouldRejectEmptyCql() {
+		new CachedPreparedStatementCreator("");
+	}
+
+	/**
+	 * @see DATACASS-253
+	 */
+	@Test(expected = IllegalArgumentException.class)
+	public void shouldRejectNullCql() {
+		new CachedPreparedStatementCreator(null);
+	}
+
+	/**
+	 * @see DATACASS-253
+	 */
+	@Test
+	public void shouldCreatePreparedStatement() {
+
+		CachedPreparedStatementCreator cachedPreparedStatementCreator = new CachedPreparedStatementCreator("my cql");
+
+		PreparedStatement result = cachedPreparedStatementCreator.createPreparedStatement(sessionMock);
+
+		assertThat(result, is(sameInstance(preparedStatement)));
+		verify(sessionMock).prepare("my cql");
+	}
+
+	/**
+	 * @see DATACASS-253
+	 */
+	@Test
+	public void shouldCacheCreatePreparedStatement() {
+
+		CachedPreparedStatementCreator cachedPreparedStatementCreator = new CachedPreparedStatementCreator("my cql");
+
+		cachedPreparedStatementCreator.createPreparedStatement(sessionMock);
+		cachedPreparedStatementCreator.createPreparedStatement(sessionMock);
+		PreparedStatement result = cachedPreparedStatementCreator.createPreparedStatement(sessionMock);
+
+		assertThat(result, is(sameInstance(preparedStatement)));
+		verify(sessionMock, times(1)).prepare("my cql");
+	}
+
+	/**
+	 * @see DATACASS-253
+	 * @throws Throwable
+	 */
+	@Test
+	public void concurrentAccessToCreateStatementShouldBeSynchronized() throws Throwable {
+
+		CreatePreparedStatementIsThreadSafe concurrentPrepareStatement = new CreatePreparedStatementIsThreadSafe(
+				preparedStatement, new CachedPreparedStatementCreator("my cql"));
+
+		runManyTimes(concurrentPrepareStatement, 5);
+	}
+
+	@SuppressWarnings("unused")
+	private static class CreatePreparedStatementIsThreadSafe extends MultithreadedTestCase {
+
+		final CachedPreparedStatementCreator preparedStatementCreator;
+		final Session session;
+		final AtomicInteger atomicInteger = new AtomicInteger();
+
+		public CreatePreparedStatementIsThreadSafe(final PreparedStatement preparedStatement,
+				CachedPreparedStatementCreator preparedStatementCreator) {
+
+			this.preparedStatementCreator = preparedStatementCreator;
+
+			this.session = newProxy(Session.class, new TestInvocationHandler() {
+
+				@Override
+				public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+
+					if (method.getName().equals("prepare") && args.length == 1) {
+
+						waitForTick(2);
+						atomicInteger.incrementAndGet();
+						return preparedStatement;
+					}
+
+					return super.invoke(proxy, method, args);
+				}
+			});
+		}
+
+		public void thread1() {
+
+			waitForTick(1);
+
+			preparedStatementCreator.createPreparedStatement(session);
+
+			assertThat(atomicInteger.get(), is(1));
+
+		}
+
+		public void thread2() {
+
+			waitForTick(1);
+
+			preparedStatementCreator.createPreparedStatement(session);
+
+			assertThat(atomicInteger.get(), is(1));
+		}
+	}
+
+	private static class TestInvocationHandler implements InvocationHandler {
+
+		@Override
+		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+
+			if (method.getName().equals("hashCode")) {
+				return hashCode();
+			}
+
+			if (method.getName().equals("equals") && args.length == 1) {
+				return equals(args[0]);
+			}
+
+			return null;
+		}
+	}
+
+	private static <T> T newProxy(Class<T> theClass, InvocationHandler invocationHandler) {
+		return (T) Proxy.newProxyInstance(CachedPreparedStatementCreatorUnitTests.class.getClassLoader(),
+				new Class[] { theClass }, invocationHandler);
+	}
+}