Spring Data JPA Merge Updated Entity

Question

I have tried for quite sometime to update an entity using Spring Boot + Spring Data JPA. I get all the right views returned to me. My edit view returns the correct entity to me by ID. Everything is moving fine .. until I actually try to save/merge/persist the object. every single time I get back a new Entity with a new ID. I just don't know why. I have looked at examples online plus the links of duplicate questions you're probably going to refer me to. So where in these pieces of code am I making the mistake?

    package demo;

    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
    import javax.persistence.Table;

    @Entity
    @Table(name = "ORDERS")
    public class Order {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private Integer id;

        @Column(name = "ORDER_NAME")
        private String name;

        @Column(name = "ORDER_DESCRIPTION")
        private String description;

        @Column(name = "ORDER_CONTENT")
        private String content;

        public Order() {}

        public Order(String name, String description, String content) {
            this.name = name;
            this.description = description;
            this.content = content;
        }

        public String getContent() {
            return content;
        }

        public String getDescription() {
            return description;
        }

        public String getName() {
            return name;
        }

        public Integer getId() {
            return this.id;
        }

        public void setContent(String content) {
            this.content = content;
        }

        public void setDescription(String description) {
            this.description = description;
        }

        public void setName(String name) {
            this.name = name;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Order other = (Order) obj;
            if (content == null) {
                if (other.content != null)
                    return false;
            } else if (!content.equals(other.content))
                return false;
            if (description == null) {
                if (other.description != null)
                    return false;
            } else if (!description.equals(other.description))
                return false;
            if (id == null) {
                if (other.id != null)
                    return false;
            } else if (!id.equals(other.id))
                return false;
            if (name == null) {
                if (other.name != null)
                    return false;
            } else if (!name.equals(other.name))
                return false;
            return true;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((content == null) ? 0 : content.hashCode());
            result = prime * result
                    + ((description == null) ? 0 : description.hashCode());
            result = prime * result + ((id == null) ? 0 : id.hashCode());
            result = prime * result + ((name == null) ? 0 : name.hashCode());
            return result;
        }

        @Override
        public String toString() {
            return "Order [id=" + id + ", name=" + name + ", description="
                    + description + ", content=" + content + "]";
        }

    }





    package demo;

    import org.springframework.data.jpa.repository.JpaRepository;

    public interface OrderRepository extends JpaRepository<Order, Integer> {

        public Order findByName(String name);


    }

package demo;

    import javax.persistence.EntityManager;
    import javax.persistence.PersistenceContext;
    import javax.transaction.Transactional;

    import org.springframework.stereotype.Service;

    @Service("customJpaService")
    public class CustomJpaServiceImpl implements CustomJpaService{

        @PersistenceContext
        private EntityManager em;

        @Transactional
        public Order saveOrUpdateOrder(Order order) {

            if (order.getId() == null) {
                em.persist(order);
            } else {
                em.merge(order);
            }
            return order;
        }

    }

package demo;

    import java.util.List;

    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.validation.BindingResult;
    import org.springframework.web.bind.annotation.ModelAttribute;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.servlet.ModelAndView;
    import org.springframework.web.servlet.mvc.support.RedirectAttributes;

    @Controller
    public class OrderController {

        //refactor to service with 
        //logging features
        @Autowired
        OrderRepository orderRepo;

        @Autowired
        CustomJpaService customJpaService;

        @RequestMapping(value="/orders", method=RequestMethod.GET)
        public ModelAndView listOrders() {

            List<Order> orders = orderRepo.findAll();

            return new ModelAndView("orders", "orders", orders);

        }

        @RequestMapping(value="/orders/{id}", method=RequestMethod.GET)
        public ModelAndView showOrder(@PathVariable Integer id, Order order) {
            order = orderRepo.findOne(id);
            return new ModelAndView("showOrder", "order", order);
        }

        @RequestMapping(value="/orders/edit/{id}", method=RequestMethod.GET)
        public ModelAndView editForm(@PathVariable("id") Integer id) {
            Order order = orderRepo.findOne(id);
            return new ModelAndView("editOrder", "order", order);
        }

        @RequestMapping(value="/updateorder", method=RequestMethod.POST)
        public String updateOrder(@ModelAttribute("order") Order order, BindingResult bindingResult, final RedirectAttributes redirectattributes) {

            if (bindingResult.hasErrors()) {
                return "redirect:/orders/edit/" + order.getId();
            }

            customJpaService.saveOrUpdateOrder(order);
            redirectattributes.addFlashAttribute("successAddNewOrderMessage", "Order updated successfully!");
            return "redirect:/orders/" + order.getId();
        }


        @RequestMapping(value="/orders/new", method=RequestMethod.GET)
        public ModelAndView orderForm() {
            return new ModelAndView("newOrder", "order", new Order());
        }

        @RequestMapping(value="/orders/new", method=RequestMethod.POST)
        public String addOrder(Order order, final RedirectAttributes redirectAttributes) {
            orderRepo.save(order);
            redirectAttributes.addFlashAttribute("successAddNewOrderMessage", "Success! Order " + order.getName() + " added successfully!");
            return "redirect:/orders/" + order.getId();
        }

    }

After this code. My view returns me to the proper URL but with an ID of 4 <-- that is a new entity. It should say 3 with the updated properties.

Answer 1

You need to store the entity somewhere between the GET request and the POST request. Your options:

1. Reload the entity from the database at the beginning of the POST and copy its properties from the POSTed entity
2. Store the entity info in hidden form variables
3. Store the entity in session

3 is the easiest solution, as it allows for optimistic concurrency control, and is more secure than hidden form vars.

2 can be good if you HMAC the hidden form variables and check that it is correct

Add @SessionAttributes("modelAttributeName") at the top of your controller, and a SessionStatus parameter to your POST handler method. Call sessionStatus.setComplete() when done. See Spring MVC: Validation, Post-Redirect-Get, Partial Updates, Optimistic Concurrency, Field Security for a working example.