Today I got myself into trouble when trying to use a DAO object inside of an event handler that was listening to a SQS queue.

Whenever my handler tried to consume a new message from the queue I got this ‘No session currently bound to execution context’ exception.

My handler was registered in the SQSListener which is provided by the sqs-dropwizard plugin.

The problem here is that the Handler is not managed by Dropwizard, what causes the hibernate session not to be bound to any context.

To solve the problem and get all the dropwizard magic to work inside the handler I had to manually bind the session to a ManagedSessionContext.

The idea is to create a method that binds a new session to the ManagedSessionContext and that takes a consumer function that will execute the event handling logic.

import org.hibernate.CacheMode;
import org.hibernate.FlushMode;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.context.internal.ManagedSessionContext;

import java.util.function.Consumer;

interface EventHandler {
    /* Necessary to wrap event handlers that needs to access the DB.         */
    /* EventHandlers are not dropwizard managed objects and thus they don't  */
    /* get a hibernate session bound to the session context.                 */
    /* This causes any attempt to use a DAO object to fail and that is why   */
    /* we need to manually bind a new session to a ManagedSessionContext so  */
    /* we can get Dropwizard magic on event handlers                         */
    default void executeWithSession(
      SessionFactory sessionFactory,
      Message message,
      Consumer<Message> consumer
    ) {
        Session session = sessionFactory.openSession();
        // DropWizard magic enabled from this point.


        // DropWizard magic disabled from this point.

And then, in your handler, you just have to wrap the code that consumes messages from the queue in a call to the executeWithSession method.

public void handle(Message message) {
  executeWithSession(sessionFactory, message, (msg) -> {
    //do whatever you need with the message in here