Merge pull request #590 from mtambara/concurrent

Add test to demonstrate concurrency problem

src/test/java/com/zaxxer/hikari/pool/ConcurrentCloseConnectionTest.java

@@ -0,0 +1,57 @@
+package com.zaxxer.hikari.pool;
+
+import com.zaxxer.hikari.HikariConfig;
+import org.junit.Test;
+
+import com.zaxxer.hikari.HikariDataSource;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+/**
+ * @author Matthew Tambara (matthew.tambara@liferay.com)
+ */
+public class ConcurrentCloseConnectionTest
+{
+   @Test
+   public void testConcurrentClose() throws Exception
+   {
+	  HikariConfig config = new HikariConfig();
+      config.setDataSourceClassName("com.zaxxer.hikari.mocks.StubDataSource");
+
+	  try (HikariDataSource ds = new HikariDataSource(config);
+	      final Connection connection = ds.getConnection()) {
+
+		  ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+		  List<Future> futures = new ArrayList<>();
+
+		  for (int i = 0; i < 500; i++) {
+			  final PreparedStatement preparedStatement =
+				  connection.prepareStatement("");
+
+			  futures.add(executorService.submit(new Callable<Void>() {
+
+				  @Override
+				  public Void call() throws Exception {
+					  preparedStatement.close();
+
+					  return null;
+				  }
+
+			  }));
+		  }
+
+		  executorService.shutdown();
+
+		  for (Future future : futures) {
+			  future.get();
+		  }
+	  }
+   }
+}