Question

I have a problem with persisting data via play-framework. Maybe it’s not possible to achive that result, but it would be really nice if it would work.

Simple: I have a complex Model (Shop with Addresses) and I want to change the shop with addresses at once and store them in the same way (shop.save()). But the error detached entity passed to persistoccurs.

Udate History
05.11

• 05.11

  • update Model Shop with attribute mappedBy="shop"
  • update link to google user group

• 09.11

  • find a workaround, but it’s ot generic

• 16.11

  • update example html form, thanks to @Pavel
  • update workaround (update 09.11) to a generic method, thanks to @mericano1
• 21.11
  • I gave up trying to find a solution and waiting for play 2.0…

Dateil:
I try to cut down the problem to a minimum:

Model:

@Entity
public class Shop extends Model {

    @Required(message = "Shopname is required")
    public String shopname;

    @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="shop")
    public List<Address> addresses;

}

@Entity
public class Address extends Model {

    @Required
    public String location;

    @ManyToOne
    public Shop shop;
}

now my Frontendcode:

#{extends 'main.html' /}

#{form @save(shop?.id)}

    <input type="hidden" name="shop.id" value="${shop?.id}"/>

    #{field 'shop.shopname'}
        <label for="shopName">Shop name:</label>
        <input type="text" name="${field.name}" 
            value="${shop?.shopname}" class="${field.errorClass}" />
    #{/field}

    <legend>Addressen</legend>
    #{list items: shop.addresses, as: "address"}
        <input type="hidden" name="shop.addresses[${address_index - 1}].id" value="${address.id}"/>
        <label>Location</label>
        <input name="shop.addresses[${address_index - 1}].location" type="text" value="${address.location}"/>
    #{/list}

     <input type="submit" class="btn primary" value="Save changes" />
#{/form}

I have just the Id from the Shop itself and the shopname to deliver via POST like: ?shop.shopname=foo

The interssting part is the list of addresses and there I have the Id and the location from the address and the result would be somthin like: ?shop.shopname=foo&shop.addresses[0].id=1&shop.addresses[0].location=bar.

Now the Controller part for the data:

public class Shops extends CRUD {

public static void form(Long id) {

    if (id != null) {
        Shop shop = Shop.findById(id);
        render(shop);
    }
    render();
}

public static void save(Long id, Shop shop) {

    // set owner manually (dont edit from FE)
    User user = User.find("byEmail", Security.connected()).first();
    shop.owner = user;

    // Validate
    validation.valid(shop);
    if (validation.hasErrors()) 
        render("@form", shop);

    shop.save();
    index();
}

Now the problem: When i change the address data the code reaches the shop.save(); the object shop is filled with all data and everything looks fine, but when hibernate tryes to persist the data, the error detached entity passed to persist occurs 🙁

I tried to change the fetch mode, the cascadetype and i also tried:

Shop shop1 = shop.merge();
shop1.save();

Unfortunately nothing worked, either the error occurs, or no address data will be stored.
Is there a way to store the data in that way?

If there is somthing not clear please write to me, I would be glad to give as much information as possible.

Update 1
I also put the problem on the google user group

Update 2 + 3
With the help of the user group (thanks to bryan w.) and an Answer from mericano1 here I found a generic workaround.

First you have to remove cascade=CascadeType.ALL from attribute addresses in shop.class. Then you have to change the method save within shops.class.

public static void save(Long id, Shop shop) {

    // set owner manually (dont edit from FE)
    User user = User.find("byEmail", Security.connected()).first();
    shop.owner = user;

    // store complex data within shop
    storeData(shop.addresses, "shop.addresses");
    storeData(shop.links, "shop.links");

    // Validate
    validation.valid(shop);
    if (validation.hasErrors()) 
        render("@form", shop);

    shop.save();
    index();
}

the generic method to store the data looks like that:

private static <T extends Model> void  storeData(List<T> list, String parameterName) {
    for(int i=0; i<list.size(); i++) {
        T relation = list.get(i);

        if (relation == null)
            continue;

        if (relation.id != null) {
            relation = (T)Model.Manager.factoryFor(relation.getClass()).findById(relation.id);
            StringBuffer buf = new StringBuffer(parameterName);
            buf.append('[').append(i).append(']');
            Binder.bind(relation, buf.toString(), request.params.all());
        }

        // try to set bidiritional relation (you need an interface or smth)
        //relation.shop = shop;
        relation.save();
    }
}

I added in Shop.class a list of Links, but I won’t update the other code snippets, so be warned if compiling errors occur.

Answer 1

When you update a complex instance in Hibernate you need to make sure it is coming from the database (fetch it first, then update that same instance) to avoid this ‘detached instance’ problem.

I generally prefer to always fetch first and then only update specific fields I’m expecting from the UI.

You can make your code a bit more generic using

(T)Model.Manager.factoryFor(relation.getClass()).findById(relation.id);