Attribute unavailable & available if request

[patcharees]

Attribute unavailable & available if request

[bkoelman]

This can be done using a resource definition. See json-api-dotnet/JsonApiDotNetCore.MongoDb#54 for an example. The second commit backports to the version you're using.

[bkoelman]

There's no looping in the code. You can ensure fields are always returned using the .Including method, which works similarly.

More importantly, JSON:API is loved by clients because it allows them to specify exactly what data to fetch and return. A server that is sending fields the client never asked for negates that optimized network bandwidth experience (between client and server, as well as between server and database). A better approach would be to break down your data structure into smaller parts, so you won't need to include/exclude so many fields.

[patcharees]

I’m newbie.
I have a lot of fields to exclude/include. Is there a better way to implement this than looping one by one?

public override SparseFieldSetExpression? OnApplySparseFieldSet(SparseFieldSetExpression? existingSparseFieldSet)
    {
        if (!_queryStringAccessor.Query.ContainsKey("fields[books]"))
        {
            return existingSparseFieldSet
                .Excluding<Book>(book => book.Refs1, ResourceGraph)
                .Excluding<Book>(book => book.Refs2, ResourceGraph)
                .Excluding<Book>(book => book.Refs3, ResourceGraph);
        }

        return existingSparseFieldSet;
    }

[patcharees]

I got it. Thanks :)

[patcharees]

I created the following method to

1. return all DefaultAttributes (primitive & string)
2. return all DefaultAttributes + specific fields by fields[]

The first case works well. But the 2nd returns only the specific fields, even though I add more attributes into existingSparseFieldSet. Do you know why?

public override SparseFieldSetExpression? OnApplySparseFieldSet(SparseFieldSetExpression? existingSparseFieldSet)
{
    //var resourceContext = ResourceGraph.GetResourceContext<TResource>();
    // set default attribute first
    var attributes = _resourceGraph.GetResourceContext<TResource>().Attributes;
    var fields = "fields[" + _resourceGraph.GetResourceContext<TResource>().PublicName + "]";

    var defaultAttributes = (IReadOnlyCollection<ResourceFieldAttribute>)
        attributes.Where(a => PageConfigurableDefinition<TResource>.IsDefaultAttribute(a)).ToList();

    if (_queryStringAccessor.Query.ContainsKey(fields) && existingSparseFieldSet != null) 
    {
        HashSet<ResourceFieldAttribute> fieldSet = existingSparseFieldSet.Fields.ToHashSet();
        foreach (var attr in defaultAttributes)
            fieldSet.Add(attr);
        return new SparseFieldSetExpression(fieldSet);
    }
    else
    {
        return new SparseFieldSetExpression(defaultAttributes);
    }
}

[patcharees]

This does not work

    public override SparseFieldSetExpression? OnApplySparseFieldSet(SparseFieldSetExpression? existingSparseFieldSet)
    {
        return existingSparseFieldSet
                .Including<Book>(t => t.bookId, ResourceGraph)
                .Including<Book>(t => t.bookGroup, ResourceGraph)
                .Including<Book>(t => t.bookGroupName, ResourceGraph);
    }

[bkoelman]

You're right, using .Including() doesn't add extra fields to the JSON response. I assumed it would, but that's not the case. It is actually by design and documented at https://www.jsonapi.net/api/JsonApiDotNetCore.Resources.IResourceDefinition-2.html#JsonApiDotNetCore_Resources_IResourceDefinition_2_OnApplySparseFieldSet_JsonApiDotNetCore_Queries_Expressions_SparseFieldSetExpression__remarks:

Including extra fields from this method will retrieve them, but not include them in the json output. This enables you to expose calculated properties whose value depends on a field that is not in the sparse fieldset.

So in that case, what you want is not possible. You'll just need to send the desired fields in the query string.