Allow data source to be reinitialized at runtime

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

@@ -33,6 +33,8 @@ public interface HikariPoolMXBean
 
    void softEvictConnections();
 
+   void reinitializeDataSource();
+
    void suspendPool();
 
    void resumePool();

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

@@ -350,6 +350,11 @@ public final class HikariPool extends PoolBase implements HikariPoolMXBean, IBag
       connectionBag.values().forEach(poolEntry -> softEvictConnection(poolEntry, "(connection evicted)", false /* not owner */));
    }
 
+   @Override
+   public void reinitializeDataSource() {
+      initializeDataSource();
+   }
+
    /** {@inheritDoc} */
    @Override
    public synchronized void suspendPool()

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

@@ -81,7 +81,7 @@ abstract class PoolBase
    private int defaultTransactionIsolation;
    private int transactionIsolation;
    private Executor netTimeoutExecutor;
-   private DataSource dataSource;
+   private AtomicReference<DataSource> dataSource;
 
    private final String catalog;
    private final String schema;
@@ -114,6 +114,7 @@ abstract class PoolBase
       this.connectionTimeout = config.getConnectionTimeout();
       this.validationTimeout = config.getValidationTimeout();
       this.lastConnectionFailure = new AtomicReference<>();
+      this.dataSource = new AtomicReference<>();
 
       initializeDataSource();
    }
@@ -193,7 +194,7 @@ abstract class PoolBase
 
    public DataSource getUnwrappedDataSource()
    {
-      return dataSource;
+      return dataSource.get();
    }
 
    // ***********************************************************************
@@ -254,7 +255,7 @@ abstract class PoolBase
    long getLoginTimeout()
    {
       try {
-         return (dataSource != null) ? dataSource.getLoginTimeout() : SECONDS.toSeconds(5);
+         return (dataSource != null) ? dataSource.get().getLoginTimeout() : SECONDS.toSeconds(5);
       } catch (SQLException e) {
          return SECONDS.toSeconds(5);
       }
@@ -324,7 +325,7 @@ abstract class PoolBase
    /**
     * Create/initialize the underlying DataSource.
     */
-   private void initializeDataSource()
+   void initializeDataSource()
    {
       final String jdbcUrl = config.getJdbcUrl();
       final String username = config.getUsername();
@@ -356,7 +357,7 @@ abstract class PoolBase
          createNetworkTimeoutExecutor(dataSource, dsClassName, jdbcUrl);
       }
 
-      this.dataSource = dataSource;
+      this.dataSource.set(dataSource);
    }
 
    /**
@@ -373,7 +374,7 @@ abstract class PoolBase
          String username = config.getUsername();
          String password = config.getPassword();
 
-         connection = (username == null) ? dataSource.getConnection() : dataSource.getConnection(username, password);
+         connection = (username == null) ? dataSource.get().getConnection() : dataSource.get().getConnection(username, password);
          if (connection == null) {
             throw new SQLTransientConnectionException("DataSource returned null unexpectedly");
          }