[jdbc-driver] Synchronize access to the handlers map (#93)

jdbc-driver/src/main/java/acolyte/jdbc/Driver.java

@@ -1,5 +1,7 @@
 package acolyte.jdbc;
 
+import java.util.Collections;
+import java.util.Map;
 import java.util.Properties;
 import java.util.HashMap;
 
@@ -31,8 +33,8 @@ public final class Driver implements java.sql.Driver {
     /**
      * Handler registry
      */
-    public static final HashMap<String,ConnectionHandler> handlers =
-        new HashMap<String,ConnectionHandler>();
+    public static final Map<String,ConnectionHandler> handlers =
+        Collections.synchronizedMap(new HashMap<String,ConnectionHandler>());
 
     // --- Shared ---
 

jdbc-driver/src/test/scala/acolyte/jdbc/DriverSpec.scala

@@ -1,10 +1,12 @@
 package acolyte.jdbc
 
-import java.util.ServiceLoader
+import java.util.{ ServiceLoader, UUID }
+import java.util.concurrent.Executors
 
 import java.sql.{ Driver ⇒ JdbcDriver, DriverManager }
 
 import scala.reflect.ClassTag
+import scala.concurrent.{ Await, ExecutionContext, ExecutionContextExecutorService, Future }
 
 import org.specs2.mutable.Specification
 
@@ -139,6 +141,26 @@ object DriverSpec extends Specification with DriverUtils with DriverFixtures {
         getStatementHandler aka "handler" mustEqual h
 
     }
+
+    "handle multi-threaded access" in {
+      import scala.concurrent.duration._
+
+      implicit val ec: ExecutionContextExecutorService =
+        ExecutionContext.fromExecutorService(Executors.newFixedThreadPool(16))
+
+      val futures =
+        (1 to 1000).map { _ =>
+          Future {
+            val handlerId = UUID.randomUUID().toString
+            acolyte.jdbc.Driver.register(handlerId, new CompositeHandler())
+            handlerId
+          }.map { handlerId =>
+            acolyte.jdbc.Driver.handlers.get(handlerId) mustNotEqual null
+          }
+        }
+
+      Await.result(Future.sequence(futures), 5.seconds)
+    }
   }
 }