public abstract class InterceptorDataSource {
   private final InvocationHandler handler;

   protected InterceptorDataSource(final DataSource delegate) {
      this.handler = new InvocationHandler() {
         public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            return (method.getName().equals("getConnection")) ? getConnection(delegate) : method.invoke(delegate, args);
         }
      };
   }

   protected Connection getConnection(final DataSource delegate) throws SQLException {
      return delegate.getConnection();
   }

   public static DataSource wrapInterceptor(InterceptorDataSource instance) {
      return (DataSource) Proxy.newProxyInstance(instance.getClass().getClassLoader(), new Class[] { DataSource.class }, instance.handler);
   }
}

// Use case for intercepting getConnection() from HikariDataSource to do something on every
// borrow from the pool
//
HikariDataSource hikariDS = new HikariDataSource();
...
DataSource wrappedDS = InterceptorDataSource.wrapInterceptor(new InterceptorDataSource(hikariDS) {
   @Override
   protected Connection getConnection(DataSource delegate) throws SQLException {
      final Connection c = super.getConnection(delegate);
      System.out.println("Look mom, I'm wrapping HikariDataSource.getConnection() before it is given to the user");
      return c;
   }
});
...

// Use case for intercepting getConnection() from the real DataSource to do something on every
// connection creation (before be added to the pool)
PGSimpleDataSource realDS = new PGSimpleDataSource(); // real DataSource to intercept
DataSource wrappedDS = InterceptorDataSource.wrapInterceptor(new InterceptorDataSource(realDS) {
   @Override
   protected Connection getConnection(DataSource delegate) throws SQLException {
      final Connection c = super.getConnection(delegate);
      System.out.println("Look mom, I'm intercepting PGSimpleDataSource.getConnection() before it reaches the pool");
      return c;
   }
});

HikariDataSource hikariDS = new HikariDataSource();
hikariDS.setDataSource(wrappedDS);
...