Hibernate - force entity to fetch id from database

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.transaction.annotation.Transactional;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

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import javax.persistence.EntityManager;

​

@Controller

public class UserController {

​

    @Autowired

    private EntityManager entityManager;

​

    @RequestMapping(value = "/users/some-action", method = {RequestMethod.GET}, produces = "text/javascript")

    @ResponseBody

    @Transactional // <----------- MUST BE @Transactional to use entityManager.refresh(entity)

    public String someAction() throws Exception {

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        UserEntity userEntity = new UserEntity();

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        // id is null

        Long idBefore = userEntity.getId();

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        entityManager.refresh(userEntity); // <-----------

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        // id is not null

        Long idAfter = userEntity.getId();

​

    }

}