GraphQL 模型在 System.Text.Json.JsonException 中挣扎

如何解决GraphQL 模型在 System.Text.Json.JsonException 中挣扎

我创建了一个新的 .NET Core 项目并安装了 GraphQL、GraphiQL 和 GraphQL.SystemTextJson 包。

运行应用程序时，这是我得到的

除了异常消息之外，GraphiQL 无法找到架构文档。

首先我有两个实体，用户和任务。

public sealed class User
{
    public Guid Id { get; set; }
}

public sealed class Task
{
    public Guid Id { get; set; }
}

并且它们都有自己的表示图类型

public sealed class UserType : ObjectGraphType<User>
{
    public UserType()
    {
        Name = nameof(User);
        Field(user => user.Id).Description("The user id.");
    }
}

public sealed class TaskType : ObjectGraphType<Task>
{
    public TaskType()
    {
        Name = nameof(Task);
        Field(task => task.Id).Description("The task id.");
    }
}

我创建了包含客户端可以执行的所有“操作”的查询

public sealed class GraphQLQuery : ObjectGraphType
{
    private readonly List<User> _users = new List<User>();
    private readonly List<Task> _tasks = new List<Task>();

    public GraphQLQuery()
    {
        Field<ListGraphType<UserType>>(
            "users","Returns a collection of users.",resolve: context => _users);

        Field<ListGraphType<TaskType>>(
            "tasks","Returns a collection of tasks.",resolve: context => _tasks);
    }
}

并为架构注册该查询

public sealed class GraphQLSchema : GraphQL.Types.Schema
{
    public GraphQLSchema(GraphQLQuery graphQLQuery,IServiceProvider serviceProvider) : base(serviceProvider)
    {
        Query = graphQLQuery;
    }
}

在 ConfigureServices 的启动文件中，我添加了此代码以在调用 services.AddControllers() 之前注册所有必需的服务

serviceCollection
        .AddSingleton<IDocumentExecuter,DocumentExecuter>()
        .AddSingleton<IDocumentWriter,DocumentWriter>()
        .AddSingleton<ISchema,GraphQLSchema>()
        .AddSingleton<GraphQLQuery>()

在 Configure 方法中，我首先调用 app.UseGraphiQl()。

对应的GraphQL请求DTO

public sealed class GraphQLRequest
{
    public string OperationName { get; set; }
    public string Query { get; set; }

    [JsonConverter(typeof(ObjectDictionaryConverter))]
    public Dictionary<string,object> Variables { get; set; }
}

最后我实现了 API 控制器

[ApiController]
[Route("[controller]")]
public sealed class GraphQLController : Controller
{
    private readonly ISchema _schema;
    private readonly IDocumentExecuter _documentExecuter;

    public GraphQLController(ISchema schema,IDocumentExecuter documentExecuter)
    {
        _schema = schema;
        _documentExecuter = documentExecuter;
    }

    public async Task<IActionResult> Post([FromBody] GraphQLRequest graphQlRequest)
    {
        Executionoptions executionoptions = new Executionoptions()
        {
            Schema = _schema,Query = graphQlRequest.Query,Inputs = graphQlRequest.Variables?.ToInputs()
        };

        ExecutionResult executionResult = await _documentExecuter.ExecuteAsync(executionoptions);

        if (executionResult.Errors != null)
            return BadRequest(executionResult);

        return Ok(executionResult);
    }
}

有人知道这里出了什么问题吗？我看不到循环依赖等问题。

---

运行应用程序时，graphQlRequest 包含以下值

• 操作名称：IntrospectionQuery
• 查询：

.

query IntrospectionQuery {
  __schema {
    queryType { name }
    mutationType { name }
    subscriptionType { name }
    types {
      ...FullType
    }
    directives {
      name
      description
      locations
      args {
        ...InputValue
      }
    }
  }
}

fragment FullType on __Type {
  kind
  name
  description
  fields(includeDeprecated: true) {
    name
    description
    args {
      ...InputValue
    }
    type {
      ...TypeRef
    }
    isDeprecated
    deprecationReason
  }
  inputFields {
    ...InputValue
  }
  interfaces {
    ...TypeRef
  }
  enumValues(includeDeprecated: true) {
    name
    description
    isDeprecated
    deprecationReason
  }
  possibleTypes {
    ...TypeRef
  }
}

fragment InputValue on __InputValue {
  name
  description
  type { ...TypeRef }
  defaultValue
}

fragment TypeRef on __Type {
  kind
  name
  ofType {
    kind
    name
    ofType {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
              }
            }
          }
        }
      }
    }
  }
}

---

我现在迁移到 .NET 5 并收到此错误

---

我添加了一个复制库

https://github.com/olaf-svenson/graphql-net-reproduction

解决方法

这是对JSON解析器经典。如果你有导航属性或性质参考海誓山盟。

通常，这可以通过任一返回映射结果，或通过调节JSON序列设置固定的。

我不能确定是否这是固定在.net核心3.1 但你可以到startup.cs添加

安装Newtonsoft Json如果已经没有。

services
  .AddControllers()
  .AddNewtonsoftJson(options =>
  {
      options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
  });

希望这能解决它。

下面是关于这个问题的一些文章。

https://dotnetcoretutorials.com/2020/03/15/fixing-json-self-referencing-loop-exceptions/

.net core 3 not having ReferenceLoopHandling in AddJsonOptions

,

您在 .Net 5 中的错误与未注册的图形类型有关。如果您在调试设置中启用所有异常并禁用“仅我的代码”，您将看到此错误

System.InvalidOperationException: 'Required service for type API.GraphTypes.UserType not found'
This exception was originally thrown at this call stack:
    GraphQL.Utilities.ServiceProviderExtensions.GetRequiredService(System.IServiceProvider,System.Type) in ServiceProviderExtensions.cs
    GraphQL.Types.Schema.CreateTypesLookup.AnonymousMethod__68_1(System.Type) in Schema.cs
    GraphQL.Types.GraphTypesLookup.Create.AnonymousMethod__0(System.Type) in GraphTypesLookup.cs
    GraphQL.Types.GraphTypesLookup.AddTypeIfNotRegistered(System.Type,GraphQL.Types.TypeCollectionContext) in GraphTypesLookup.cs
    GraphQL.Types.GraphTypesLookup.HandleField(GraphQL.Types.IComplexGraphType,GraphQL.Types.FieldType,GraphQL.Types.TypeCollectionContext,bool) in GraphTypesLookup.cs
    GraphQL.Types.GraphTypesLookup.AddType(GraphQL.Types.IGraphType,GraphQL.Types.TypeCollectionContext) in GraphTypesLookup.cs
    GraphQL.Types.GraphTypesLookup.Create(System.Collections.Generic.IEnumerable<GraphQL.Types.IGraphType>,System.Collections.Generic.IEnumerable<GraphQL.Types.DirectiveGraphType>,System.Func<System.Type,GraphQL.Types.IGraphType>,GraphQL.Conversion.INameConverter,bool) in GraphTypesLookup.cs
    GraphQL.Types.Schema.CreateTypesLookup() in Schema.cs
    System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

将 UserType 和 TaskType 添加到 DI 容器可以解决此错误。

现在，您的原始问题是：您应该使用 IDocumentWriter 来编写响应，您不能仅通过返回 executionResult 来序列化 Ok(executionResult)。 使用此代码编写响应（从官方 graphql-dotnet/examples 存储库中窃取）：

private async Task WriteResponseAsync(HttpContext context,ExecutionResult result)
{
    context.Response.ContentType = "application/json";
    context.Response.StatusCode = result.Errors?.Any() == true ? (int)HttpStatusCode.BadRequest : (int)HttpStatusCode.OK;

    await _documentWriter.WriteAsync(context.Response.Body,result);
}

更新后的GraphQLController.cs

[ApiController]
[Route("[controller]")]
public sealed class GraphQLController : Controller
{
    private readonly ISchema _schema;
    private readonly IDocumentExecuter _documentExecuter;
    private readonly IDocumentWriter _documentWriter;

    public GraphQLController(ISchema schema,IDocumentExecuter documentExecuter,IDocumentWriter documentWriter)
    {
        _schema = schema;
        _documentExecuter = documentExecuter;
        _documentWriter = documentWriter;
    }

    public async Task Post([FromBody] GraphQLRequest graphQlRequest)
    {
        ExecutionOptions executionOptions = new ExecutionOptions()
        {
            Schema = _schema,Query = graphQlRequest.Query,Inputs = graphQlRequest.Variables?.ToInputs()
        };

        ExecutionResult executionResult = await _documentExecuter.ExecuteAsync(executionOptions);

        await WriteResponseAsync(HttpContext,executionResult);
    }

    private async Task WriteResponseAsync(HttpContext context,ExecutionResult result)
    {
        context.Response.ContentType = "application/json";
        context.Response.StatusCode = result.Errors?.Any() == true ? (int)HttpStatusCode.BadRequest : (int)HttpStatusCode.OK;
    
        await _documentWriter.WriteAsync(context.Response.Body,result);
    }
}