A simple service using spring's @transactional and dependency injection.

FakeService.java

package au.com.permeance.service;

public interface FakeService {

    void doStuff() throws Exception;

}

FakeServiceImpl.java

package au.com.permeance.service.impl;

import au.com.permeance.service.FakeService;
import com.liferay.portal.service.UserLocalService;
import com.liferay.portal.util.Portal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class FakeServiceImpl implements FakeService {

    private final Portal portal;

    private final UserLocalService userLocalService;

    @Autowired
    public FakeServiceImpl(Portal portal,
                           UserLocalService userLocalService) {
        this.portal = portal;
        this.userLocalService = userLocalService;
    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public void doStuff() throws Exception {
        userLocalService.getDefaultUser(portal.getDefaultCompanyId());
        throw new RuntimeException("Don't really delete that user");
    }

}