How to restrict the single root node in Access Group

Support
#1

Hi,
I am creating an application, where i want to restrict the user to create one single root node in access group. Now in the Access Group hierarchy, it has a possible of creating multiple root nodes. So, plz suggest me how to accomplish this…
Thank you…

#2

Hi Vimal,
Usually such tasks are performed by Entity Listeners. In your case, the problem is a bit more complicated, because you need an entity listener for the entity not belonging to your project - Group, which is provided by the platform.
So, when creating the listener in Studio, keep the Use for entities list empty:
image

To register the listener for the Group entity, make it also a listener of the AppContextInitializedEvent lifecycle event and register it in the EntityListenerManager. In the onBeforeInsert/onBeforeUpdate methods, check if a root group is already present and throw an exception. If you want to show a nice notification to users, create your own exception class and use Client-Level Exception Handlers to display an appropriate message.

package com.company.playground.listener;

import com.haulmont.cuba.core.EntityManager;
import com.haulmont.cuba.core.global.Events;
import com.haulmont.cuba.core.listener.BeforeInsertEntityListener;
import com.haulmont.cuba.core.listener.BeforeUpdateEntityListener;
import com.haulmont.cuba.core.sys.events.AppContextInitializedEvent;
import com.haulmont.cuba.core.sys.listener.EntityListenerManager;
import com.haulmont.cuba.security.entity.Group;
import org.springframework.context.event.EventListener;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import javax.inject.Inject;
import java.util.List;

@Component("playground_MyGroupEntityListener")
public class MyGroupEntityListener implements BeforeInsertEntityListener<Group>, BeforeUpdateEntityListener<Group> {

    @Inject
    private EntityListenerManager entityListenerManager;

    @EventListener(AppContextInitializedEvent.class) // notify after AppContext is initialized
    @Order(Events.LOWEST_PLATFORM_PRECEDENCE + 100)  // run after all platform listeners
    public void initEntityListeners() {
        entityListenerManager.addListener(Group.class, "playground_MyGroupEntityListener");
    }

    @Override
    public void onBeforeInsert(Group entity, EntityManager entityManager) {
        checkRootItemExists(entity, entityManager);
    }

    @Override
    public void onBeforeUpdate(Group entity, EntityManager entityManager) {
        checkRootItemExists(entity, entityManager);
    }

    private void checkRootItemExists(Group group, EntityManager entityManager) {
        if (group.getParent() != null)
            return;

        List<Group> list = entityManager.createQuery(
                "select g from sec$Group g where g.parent is null", Group.class).getResultList();
        if (!list.isEmpty() && !list.get(0).equals(group)) {
            throw new RuntimeException("A root group already exists");
        }
    }
}