Capture RowStreamImpl endHandler in a synchronized block (#1581)

* Capture RowStreamImpl endHandler in a synchronized block

Follows-up on #1577

The endHandler was no longer captured safely after changes in the previous PR.

Signed-off-by: Thomas Segismont <[email protected]>

* RowStream handler should be invoked out the synchronized block

It's safer not to hold a lock on the stream instance while invoking user code.

Signed-off-by: Thomas Segismont <[email protected]>

---------

Signed-off-by: Thomas Segismont <[email protected]>

Author: tsegismont

vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/RowStreamImpl.java

@@ -174,13 +174,13 @@ private void checkPending() {
       emitting = true;
     }
     while (true) {
+      Handler handler;
+      Object event;
       synchronized (RowStreamImpl.this) {
         if (demand == 0L) {
           emitting = false;
           break;
         }
-        Handler handler;
-        Object event;
         if (result != null) {
           handler = rowHandler;
           event = result.next();
@@ -203,8 +203,9 @@ private void checkPending() {
               break;
             } else {
               cursor.close();
+              Handler<Void> eh = endHandler;
               handler = v -> {
-                endHandler.handle(null);
+                eh.handle(null);
                 synchronized (RowStreamImpl.this) {
                   cursor = null;
                 }