CODEWITHSUNDEEP
c#.netnhibernatecachingserialization
Gabriel Monteiro Nepomuceno
Gabriel Monteiro Nepomuceno

Reputation: 1244

Serializing Nhibernate entities to json serialize too much

I have a problem I'm already trying to solve for some time.

The scenario is as follows

The person will make an insertion of a new entity in the database.

To begin insertion is necessary that I make a costly transformation from an xml file to fill some basic properties.

I wanted to process this xml before and store the object already transformed as o object in some short of cache.

After that, the process of filling the other properties of this object is very time consuming and I want the person could stop in the middle and back to end it after. however I can not save this object in the database incomplete, due to some validations that are made in the database when this object is inserted.

The solution I had tidied involved serialize the object when the person stop filling it, even if it is not done yet,than when the person come back to continue filling i would deserialize the object so the person could continue.

The problem is that when i try to serialize this object nihibernate serialize almost the entire database because of the lazy load and i get stackoverlow error ( lol it is funny to say this error here lol ).

Does anyone have any idea what I should do?

One of the things I had done was to keep the object in the cache (don't know how the /net 4 cache serialized it but seams to work) however everytime I retrieve the object it loses half of children objects, and always exactly half the children ....

if is live I have a order with 20 items if i try to get it back from the cache it will come back with 10 items if i try to retrieve it again I would got the order with only 5 itens.

Does anyone have any idea how to solve this?

already tries there

NHibernate serializing lazy-loaded entities with WCF

Serialize nHibernate query to JSON

Upvotes: 0

Views: 1958

Answers (1)

Rippo
Rippo

Reputation: 22424

One way is to project what you do want first then serialise the result into a DTO.

However by doing this you run into an issue where you are creating DTO's with lots of setters/getters. Wouldn't it be easier to create a simple anonymous type and serialise that instead? I have written a blog post that explains this. 

//first create our anonymous type DTO
var dto = new { 
    Id = 0L, 
    Source = string.Empty, 
    Destination = string.Empty, 
    Is301 = false
};

//notice the ListAs(dto) extension method
var model = Session.QueryOver<CmsRedirect>()
  .SelectList(s => s
    .Select(x => x.Id).WithAlias(() => dto.Id)
    .Select(x => x.Source).WithAlias(() => dto.Source)
    .Select(x => x.Destination).WithAlias(() => dto.Destination)
    .Select(x => x.Do301).WithAlias(() => dto.Is301)
  )
  .Take(take).Skip(page * pageSize)
  .ListAs(dto);

return Json(new { Total = total, List = model }, 
    JsonRequestBehavior.AllowGet);

ListAs is a simple(ish) extension method. (credit goes to Filip Kinský)

public static class NHibernateExtensions {
  public static IList<TRes> ListAs<TRes>(
      this IQueryOver qry, TRes resultByExample) {

    var ctor = typeof(TRes).GetConstructors().First();

    return qry.UnderlyingCriteria
      .SetResultTransformer(
        Transformers.AliasToBeanConstructor(
         (ConstructorInfo) ctor)
        ).List<TRes>();
  }
}

But be warned in my example I do not serialise children collections so you may need to handle this manually yourself.

Upvotes: 1

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