Fixes #793 introduce new methods for scheduled executor service that

takes/returns ScheduledExecutorService interface instances.

src/main/java/com/zaxxer/hikari/HikariConfig.java

@@ -16,6 +16,10 @@
 
 package com.zaxxer.hikari;
 
+import static com.zaxxer.hikari.util.UtilityElf.getNullIfEmpty;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -25,6 +29,7 @@ import java.lang.reflect.Modifier;
 import java.util.Properties;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
 
@@ -40,11 +45,6 @@ import com.codahale.metrics.health.HealthCheckRegistry;
 import com.zaxxer.hikari.metrics.MetricsTrackerFactory;
 import com.zaxxer.hikari.util.PropertyElf;
 
-import static java.util.concurrent.TimeUnit.MINUTES;
-import static java.util.concurrent.TimeUnit.SECONDS;
-
-import static com.zaxxer.hikari.util.UtilityElf.getNullIfEmpty;
-
 public class HikariConfig implements HikariConfigMXBean
 {
    private static final Logger LOGGER = LoggerFactory.getLogger(HikariConfig.class);
@@ -90,7 +90,7 @@ public class HikariConfig implements HikariConfigMXBean
    private DataSource dataSource;
    private Properties dataSourceProperties;
    private ThreadFactory threadFactory;
-   private ScheduledThreadPoolExecutor scheduledExecutor;
+   private ScheduledExecutorService scheduledExecutor;
    private MetricsTrackerFactory metricsTrackerFactory;
    private Object metricRegistry;
    private Object healthCheckRegistry;
@@ -718,9 +718,10 @@ public class HikariConfig implements HikariConfigMXBean
     *
     * @return the executor
     */
+   @Deprecated
    public ScheduledThreadPoolExecutor getScheduledExecutorService()
    {
-      return scheduledExecutor;
+      return (ScheduledThreadPoolExecutor) scheduledExecutor;
    }
 
    /**
@@ -728,11 +729,32 @@ public class HikariConfig implements HikariConfigMXBean
     *
     * @param executor the ScheduledExecutorService
     */
+   @Deprecated
    public void setScheduledExecutorService(ScheduledThreadPoolExecutor executor)
    {
       this.scheduledExecutor = executor;
    }
 
+   /**
+    * Get the ScheduledExecutorService used for housekeeping.
+    *
+    * @return the executor
+    */
+   public ScheduledExecutorService getScheduledExecutor()
+   {
+      return scheduledExecutor;
+   }
+
+   /**
+    * Set the ScheduledExecutorService used for housekeeping.
+    *
+    * @param executor the ScheduledExecutorService
+    */
+   public void setScheduledExecutor(ScheduledExecutorService executor)
+   {
+      this.scheduledExecutor = executor;
+   }
+   
    public String getTransactionIsolation()
    {
       return transactionIsolationName;

src/main/java/com/zaxxer/hikari/pool/HikariPool.java

@@ -41,6 +41,7 @@ import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
@@ -92,7 +93,7 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
    private final ProxyLeakTask leakTask;
    private final SuspendResumeLock suspendResumeLock;
 
-   private ScheduledThreadPoolExecutor houseKeepingExecutorService;
+   private ScheduledExecutorService houseKeepingExecutorService;
    private ScheduledFuture<?> houseKeeperTask;
 
    /**
@@ -537,20 +538,21 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
 
    private void initializeHouseKeepingExecutorService()
    {
-      if (config.getScheduledExecutorService() == null) {
+      if (config.getScheduledExecutor() == null) {
          final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElse(new DefaultThreadFactory(poolName + " housekeeper", true));
-         this.houseKeepingExecutorService = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
-         this.houseKeepingExecutorService.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
-         this.houseKeepingExecutorService.setRemoveOnCancelPolicy(true);
+         final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
+         executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
+         executor.setRemoveOnCancelPolicy(true);
+         this.houseKeepingExecutorService = executor;
       }
       else {
-         this.houseKeepingExecutorService = config.getScheduledExecutorService();
+         this.houseKeepingExecutorService = config.getScheduledExecutor();
       }
    }
 
    private void destroyHouseKeepingExecutorService()
    {
-      if (config.getScheduledExecutorService() == null) {
+      if (config.getScheduledExecutor() == null) {
          houseKeepingExecutorService.shutdownNow();
       }
    }