Example SDL Tridion .Net templates to create a JSON file as a package item and then publish it as a binary variant

CreateTestData.cs

using Tridion.ContentManager.Templating;
using Tridion.ContentManager.Templating.Assembly;

namespace Test.JsonTemplates
{
    class CreateTestData : ITemplate
    {
        public void Transform(Engine engine, Package package)
        {
            string JSON = "{\"h3title\":\"09/04/2013\"}";
            var jsonItem = package.CreateStringItem(ContentType.Unknown, JSON);
            jsonItem.Properties.Add(Item.ItemPropertyFileName, "test");
            jsonItem.Properties.Add(Item.ItemPropertyFileNameExtension, "json");
            package.PushItem("test.json", jsonItem);
        }
    }
}

PublishJsonFiles.cs

using System;
using Tridion.ContentManager;
using Tridion.ContentManager.CommunicationManagement;
using Tridion.ContentManager.Templating;
using Tridion.ContentManager.Templating.Assembly;

namespace Test.JsonTemplates
{
    [TcmTemplateTitle("Publish JSON package items as Variants")]
    public class PublishJsonFiles : ITemplate
    {
        public void Transform(Engine engine, Package package)
        {
            //Get all items of unknown type from the package
            var items = package.GetAllByType(ContentType.Unknown);

            //Remove all items that are NOT JSON files
            foreach (var item in items)
            {
                if (!item.Properties[Item.ItemPropertyFileNameExtension].Equals("json", StringComparison.OrdinalIgnoreCase))
                {
                    items.Remove(item);
                }
            }

            //Check the package values for an optional structure group ID to publish to
            var optionalStructureGroupId = package.GetValue("jsonStructureGroup");
            StructureGroup jsonStructureGroup = null;

            //Go get the structure group from Tridion if an Id has been specified
            if (!String.IsNullOrWhiteSpace(optionalStructureGroupId))
            {
                var structureGroupTcmUri = new TcmUri(
                    Convert.ToInt32(optionalStructureGroupId),
                    ItemType.StructureGroup,
                    engine.PublishingContext.RenderedItem.ResolvedItem.Item.Id.PublicationId);
                jsonStructureGroup = (StructureGroup)engine.GetObject(structureGroupTcmUri);
            }

            //Publish out the JSON files
            foreach (var item in items)
            {
                var filename = item.Properties[Item.ItemPropertyFileName] + "." + item.Properties[Item.ItemPropertyFileNameExtension];

                //If no structure group has been specified, publish to the default images directory configured for the publication
                if (jsonStructureGroup == null)
                {
                    engine.PublishingContext.RenderedItem.AddBinary(
                        item.GetAsStream(),
                        filename,
                        filename,
                        null,
                        "application/json");
                }
                else
                {
                    engine.PublishingContext.RenderedItem.AddBinary(
                        item.GetAsStream(),
                        filename,
                        jsonStructureGroup,
                        filename,
                        null,
                        "application/json");
                }
            }
        }
    }
}