使用新的 .net-core-3 json 序列化程序进行依赖注入

Question

我使用这个合约解析器进行依赖注入 Autofac 和 Json.NET：

public class AutofacContractResolver : DefaultContractResolver
{
    private readonly IComponentContext _container;

    public AutofacContractResolver(IComponentContext context)
    {
        _container = context ?? throw new ArgumentNullException(nameof(context));
    }

    protected override JsonObjectContract CreateObjectContract(Type objectType)
    {
        var contract = base.CreateObjectContract(objectType);

        // use Autofac to create types that have been registered with it
        if (_container.IsRegistered(objectType))
        {
            contract.DefaultCreator = () => _container.Resolve(objectType);
        }

        return contract;
    }
}

然后，我用它和 DI 来初始化 JsonSerializer:

var contractResolver = ctx.Resolve<IContractResolver>(); // ctx = Autofac's IComponentContext

var jsonSerializer = new JsonSerializer
{
    ContractResolver = contractResolver, // <-- AutofacContractResolver 
};

---

这种技术与net-core-3.0 中的新System.Text.Json 的等价物是什么——如果已经有的话？我无法弄清楚这一点，也找不到任何与此类似的接口。

Answer 1

请尝试我作为 System.Text.Json 的扩展编写的这个库，以提供缺少的功能：https://github.com/dahomey-technologies/Dahomey.Json。

您会发现对编程对象映射的支持。

定义您自己的 IObjectMappingConvention 实现：

public class AutofacObjectMappingConvention : IObjectMappingConvention
{
    private readonly IComponentContext _container;

    public AutofacObjectMappingConvention(IComponentContext context)
    {
        _container = context ?? throw new ArgumentNullException(nameof(context));
    }


    public void Apply<T>(JsonSerializerOptions options, ObjectMapping<T> objectMapping) where T : class
    {
        defaultObjectMappingConvention.Apply<T>(options, objectMapping);

        // use Autofac to create types that have been registered with it
        if (_container.IsRegistered(objectType))
        {
            objectMapping.MapCreator(o => _container.Resolve<T>());
        }
    }
}

实现 IObjectMappingConventionProvider 以将多个类型与约定关联：

public class AutofacObjectMappingConventionProvider : IObjectMappingConventionProvider
{
    public IObjectMappingConvention GetConvention(Type type)
    {
        // here you could filter which type should be instantiated by autofac and return null for other types
        return new AutofacObjectMappingConvention();
    }
}

通过调用命名空间 Dahomey.Json 中定义的扩展方法 SetupExtensions 的 JsonSerializerOptions 来设置 json 扩展：

JsonSerializerOptions options = new JsonSerializerOptions();
options.SetupExtensions();

为类注册新的对象映射约定：

options.GetObjectMappingConventionRegistry().RegisterProvider(new AutofacObjectMappingConventionProvider());

然后使用常规的 Sytem.Text.Json API 序列化您的类：

string json = JsonSerializer.Serialize(myClass, options);