Odata Webapi - 如何在 7.0 核心中注入(inject) ODataResourceDeserializer？

Question

文档非常稀少，我尝试的所有结果都注入(inject)了反序列化器，但正常的 odata url 不再起作用。

https://github.com/OData/WebApi/issues/158有 5.6 的解决方案。

最后的相关评论是:

@dbenzhuser - In that commit, look at ODataFormatterTests.cs for how inject a custom deserializer/deserializer provider. You can still use a custom DeserializerProvider but it's injected through DI instead of injecting it through ODataMediaTypeFormatters.

这是毫无意义的。我在那里尝试了代码，但正如我所说，它破坏了 URL。

现在我的 Odata 设置很简单:

    services.AddMvc()
        .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    services.AddOData();

\UnitTest\Microsoft.AspNet.OData.Test.Shared\Formatter\ODataFormatterTests.cs

有注入(inject)它们的示例(如第 379-383 行)

        config.MapODataServiceRoute("IgnoredRouteName", null, builder =>
            builder.AddService(Microsoft.OData.ServiceLifetime.Singleton, sp => ODataTestUtil.GetEdmModel())
                .AddService<ODataSerializerProvider>(ServiceLifetime.Singleton, sp => new CustomSerializerProvider())
                .AddService<IEnumerable<IODataRoutingConvention>>(ServiceLifetime.Singleton, sp =>
                    ODataRoutingConventions.CreateDefaultWithAttributeRouting("IgnoredRouteName", config)));

但如果不删除核心 odata 路由，我似乎无法使其正常工作。

有人知道如何在不破坏基本功能的情况下将其用于当前版本吗？

Answer 1

如果要维护基本功能，则需要三个步骤:

您的 DeserializerProvider 实现应默认为您的自定义 Deserializer 无法管理的所有场景的基本实现。在以下示例中，自定义反序列化器仅对资源而不是集合进行操作:

public class EntityTypeDeserializerProvider : DefaultODataDeserializerProvider
{
    private readonly DataContractDeserializer _dataContractDeserializer;
    public EntityTypeDeserializerProvider(IServiceProvider rootContainer)
        : base(rootContainer)
    {
        _dataContractDeserializer = new DataContractDeserializer(this);
    }

    public override ODataEdmTypeDeserializer GetEdmTypeDeserializer(IEdmTypeReference edmType)
    {
        if(edmType.Definition.TypeKind == EdmTypeKind.Complex || edmType.Definition.TypeKind == EdmTypeKind.Entity)
            return _dataContractDeserializer;
        else 
            return base.GetEdmTypeDeserializer(edmType);
    }
}

与提供者一样，您的自定义 _Deserializer 应该为您不需要自定义的所有内容调用基本实现。在下面的实现中，我们只尝试强制执行反序列化的属性的顺序以及调用 DataContract OnDeserializing和 OnDeserialized方法，其余的反序列化不受影响:

/// <summary>
/// OData serializer that oberys the DataMember Order Attribute and OnDeserializing and OnDeserialized attributes on the resource definition
/// </summary>
public class DataContractDeserializer : ODataResourceDeserializer
{
    public DataContractDeserializer(ODataDeserializerProvider provider)
        : base(provider) { }

    public override object CreateResourceInstance(IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)
    {
        var resource = base.CreateResourceInstance(structuredType, readContext);
        var type = resource.GetType();
        if(type.GetCustomAttributesData().Any(x => x.AttributeType == typeof(DataContractAttribute)))
        {
            // manually call OnDeserializing
            var init = type.GetMethods(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic).FirstOrDefault(x => x.GetCustomAttributesData().Any(a => a.AttributeType == typeof(OnDeserializingAttribute)));
            if(init != null)
            {
                init.Invoke(resource, new object[] { new StreamingContext(StreamingContextStates.Remoting, readContext ) });
            }
        }
        return resource;
    }

    public override object ReadResource(ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)
    {
        var resource = base.ReadResource(resourceWrapper, structuredType, readContext);
        var type = resource.GetType();
        if (type.GetCustomAttributesData().Any(x => x.AttributeType == typeof(DataContractAttribute)))
        {
            // manually call OnDeserialized
            var final = type.GetMethods(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic).FirstOrDefault(x => x.GetCustomAttributesData().Any(a => a.AttributeType == typeof(OnDeserializedAttribute)));
            if (final != null)
            {
                final.Invoke(resource, new object[] { new StreamingContext(StreamingContextStates.Remoting, readContext) });
            }
        }
        return resource;
    }
    public override void ApplyStructuralProperties(object resource, ODataResourceWrapper resourceWrapper, IEdmStructuredTypeReference structuredType, ODataDeserializerContext readContext)
    {
        var type = resource.GetType();
        var memberDescriptors = type.GetProperties().Where(x => x.HasAttribute<DataMemberAttribute>());
        if (memberDescriptors.Any())
        {
            var orderedProperties = from p in resourceWrapper.Resource.Properties
                                    let clsProperty = memberDescriptors.FirstOrDefault(m => m.Name == p.Name)
                                    let memberAtt = (DataMemberAttribute)(clsProperty?.GetCustomAttributes(true).FirstOrDefault(a => a.GetType() == typeof(DataMemberAttribute)))
                                    orderby (memberAtt?.Order).GetValueOrDefault()
                                    select p;
            foreach (var property in orderedProperties)
            {
                ApplyStructuralProperty(resource, property, structuredType, readContext);
            }
        }
        else
            base.ApplyStructuralProperties(resource, resourceWrapper, structuredType, readContext);
    }
}

最后，您需要将默认的 DeserializerProvider 注册替换为自己的，以下是重载到 MapODataServiceRoute 的示例它注册了前面 2 个示例中的 DeserializerProvider。
我已经注释掉了注册特定 SerializerProvider 的示例

private static ODataRoute MapODataServiceRoute(this HttpConfiguration configuration, string routeName,
    string routePrefix, IEdmModel model, ODataBatchHandler batchHandler = null, ODataUriResolver uriResolver = null, IList<IODataRoutingConvention> routingConventions = null)
{
     return configuration.MapODataServiceRoute(routeName, routePrefix, builder =>
         builder
             .AddService(ServiceLifetime.Singleton, sp => model)
             //.AddService<ODataSerializerProvider>(ServiceLifetime.Singleton, sp => new DefaultODataSerializerProvider(sp))
             .AddService<ODataDeserializerProvider>(ServiceLifetime.Singleton, sp => new EntityTypeDeserializerProvider(sp))
             .AddService(ServiceLifetime.Singleton, sp => batchHandler ?? new DefaultODataBatchHandler(GlobalConfiguration.DefaultServer))
             .AddService(ServiceLifetime.Singleton, sp => uriResolver ?? new ODataUriResolver())
             .AddService<IEnumerable<IODataRoutingConvention>>(ServiceLifetime.Singleton, sp =>
                     routingConventions ??
                         ODataRoutingConventions.CreateDefaultWithAttributeRouting(routeName, configuration)
                    )
                );
    }