how to eliminate auto generated select queries when executing EntityManager.merge

[vonrosen]

I'm fairly new to Spring so please bear with me. I have two Spring MVC Controllers, a Register controller and EditProfile controller. The Register controller allows a user to register (inserts a new User using entityManager.persist) and the EditProfile controller updates a logged in user (using entityManager.merge). When a user's profile is updated using merge, two select queries are automatically issued before the SQL update. I believe this is to reattach the user object to the PersistenceContext since merge (I believe) works only on attached objects. My question is: How can I eliminate the two select queries from being issued? This seems like an unecessary performance hit.

Here is my EditProfile controller.

package com.idream.servlet;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;

import com.idream.manager.StateManager;
import com.idream.manager.UserManager;
import com.idream.model.Role;
import com.idream.model.User;

@Controller
@RequestMapping(value="/editprofile")
public class EditProfile {

	@Autowired
	private UserManager userManager;
	
	@Autowired
	private StateManager stateManager;
	
	@RequestMapping(method = RequestMethod.GET)
	public String setupForm(Model model, HttpServletRequest request) {
		
		model.addAttribute("stateList", stateManager.getStatesForDropdown());
		model.addAttribute("user", request.getSession().getAttribute("user"));
		
		return "editprofile/edit";
	}	
	
	
	private void updateSessionUser(User user, HttpServletRequest request) {
		
		User sessionUser = (User)request.getSession().getAttribute("user");
		
		sessionUser.setFirstName(user.getFirstName());
		sessionUser.setLastName(user.getLastName());
		sessionUser.setAddress1(user.getAddress1());
		sessionUser.setAddress2(user.getAddress2());
		sessionUser.setCity(user.getCity());
		sessionUser.setState(user.getState());
		sessionUser.setZipCode(user.getZipCode());
		sessionUser.setAutoSave(user.getAutoSave());
		
		
	}
	
	private void 
			fixUpModelUser(User springModelUser, 
					User sessionUser) {

		/**
		 * update the spring model user so that it can be persisted.
		 * it needs the fields that aren't updated by the form (email password)
		 * and the user id (so that jpa can detect that's it's already
		 * there and update not insert)
		 */
		springModelUser.setUserId(sessionUser.getUserId());
		springModelUser.setEmail(sessionUser.getEmail());
		springModelUser.setPassword(sessionUser.getPassword());
		
		Role r = new Role();
		r.setRoleId(1);
		springModelUser.setRole(r); //set role to customer
		
		
	}
	
	@RequestMapping(method = RequestMethod.POST)
	/**
	public String onSubmit(@ModelAttribute("user") User user, BindingResult result, Model model,
			HttpServletRequest request) {
	 */
	
	public String onSubmit(@ModelAttribute("user") User user, BindingResult result, Model model,
				HttpServletRequest request) {
		
		
		
		fixUpModelUser(user, (User)request.getSession().getAttribute("user"));
		//updateSessionUser(user, request);
		
		//User u = (User)request.getSession().getAttribute("user");
		
		//user.setUserId(u.getUserId()); //update the spring user so it has a user id, this way
		
		//it can be updated by jpa
		
		//System.out.println(u.getUserId());
		
		model.addAttribute("stateList", stateManager.getStatesForDropdown());
		
		if (user.getState() != null && user.getState().trim().equals("NONE")) {
			user.setState(null);
		}
		
		userManager.mergeUser(user);
		//userManager.flush();
		
		//update session user to have new values that were entered into the form
		
		updateSessionUser(user, request);		
		
		return "editprofile/edit";
	}
	
}

Here is the UserManager

package com.idream.manager;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;
import javax.persistence.Query;

import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import com.idream.model.User;


@Transactional
public class UserManager {

	//@PersistenceContext(type=PersistenceContextType.TRANSACTION)
	@PersistenceContext
	private EntityManager em;
	

	@PersistenceContext public void setEntityManager(EntityManager em) { this.em = em; }
	
	//@Transactional(readOnly = true)
	@SuppressWarnings("unchecked")
	public User getUserByEmail(String email) {
		Query query = this.em.createQuery("SELECT user FROM User user where user.email = :email1 ");
		
		query.setParameter("email1", email);
		
		List list = query.getResultList();
		
		if (list == null || list.size() == 0) return null;
		
		return (User)list.get(0);
	}


	
	public void persistUser(User user) {
		
		this.em.persist(user);
		
		
	}
	
	//@Transactional(propagation = Propagation.REQUIRED)

	public User mergeUser(User user) {
		
	
		//EntityTransaction t = em.getTransaction();
		
		
		
		User merged = this.em.merge(user);
		this.em.flush();
		
		
		return merged;
	}
	
	public void flush() {
		this.em.flush();		
	}
	
	
	
}

Here is the sql logging of the queries that are issued when the merge and flush occurs:

Hibernate: select user0_.user_id as user1_1_0_, user0_.address1 as address2_1_0_, user0_.address2 as address3_1_0_, user0_.auto_save as auto4_1_0_, user0_.city as city1_0_, user0_.date_saved as date6_1_0_, user0_.email as email1_0_, user0_.first_name as first8_1_0_, user0_.last_name as last9_1_0_, user0_.password as password1_0_, user0_.role_id as role14_1_0_, user0_.state as state1_0_, user0_.verified as verified1_0_, user0_.zip_code as zip13_1_0_ from User user0_ where user0_.user_id=?
Hibernate: select role0_.role_id as role1_4_0_, role0_.date_saved as date2_4_0_, role0_.role_name as role3_4_0_ from Role role0_ where role0_.role_id=?
Hibernate: update User set address1=?, address2=?, auto_save=?, city=?, date_saved=?, email=?, first_name=?, last_name=?, password=?, role_id=?, state=?, verified=?, zip_code=? where user_id=?

The code that generates the log messages is in the UserManager.

public User mergeUser(User user) {
		
		User merged = this.em.merge(user);
		this.em.flush();
		
		
		return merged;
	}