GraphQL 既是一種用於 API 的查詢語言也是一個滿足你數據查詢的運行時。GraphQL 對你的 API 中的數據提供了一套易於理解的完整描述,使得客戶端能夠準確地獲得它需要的數據,而且沒有任何冗餘,也讓 API 更容易地隨着時間推移而演進,還能用於構建強大的開發者工具。
——出自 https://graphql.cn
HotChocolate可以通過自定義Directive來對字段的值進行轉換和處理,下在的例子就是給字符串給字符串類型的值轉大寫和替換。
using HotChocolate;
using HotChocolate.Data;
using HotChocolate.Execution;
using HotChocolate.Types;
using System;
using System.Collections.Generic;
using System.Reflection;
namespace GraphQLBase003
{
class Program
{
static void Main(string[] args)
{
DirectiveDemo.Run();
}
}
public class DirectiveDemo
{
public static void Run()
{
var schema = SchemaBuilder.New()
.AddProjections()
.AddQueryType<Query>()
.AddDirectiveType<UpperDirectiveType>()
.AddDirectiveType<ReplaceDirectiveType>()
.Create();
var executor = schema.MakeExecutable();
Console.WriteLine("原name=abcde ");
Console.WriteLine("--------------轉大寫-------------------");
Console.WriteLine(executor.Execute("{ student{id name @upper(name:\"this is test\") age} }").ToJson());
Console.WriteLine("--------------a替換成1 -------------------");
Console.WriteLine(executor.Execute("{ student{id name @replace(old:\"a\",new:\"1\") age} }").ToJson());
Console.WriteLine("--------------然後全部轉大寫-.a替換成1 -------------------");
Console.WriteLine(executor.Execute("{ student{id name @upper(name:\"this is test\") @replace(old:\"a\",new:\"1\") age} }").ToJson());
Console.WriteLine("--------------a替換成1.然後全部轉大寫-------------------");
Console.WriteLine(executor.Execute("{ student{id name @replace(old:\"a\",new:\"1\") @upper(name:\"this is test\") age} }").ToJson());
}
public class Query
{
[UseProjection]
public Student GetStudent()
{
return new Student
{
Id = 1,
Name = "abcde",
Age = 234
};
}
[UseProjection]
public List<Student> GetStudents()
{
return new List<Student>{
new Student
{
Id = 100,
Name = "aBcD",
Age=10
},
new Student
{
Id = 101,
Name = "EFGH",
Age=20
}
};
}
}
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
public class UpperDirectiveType : DirectiveType<UpperDirective>
{
protected override void Configure(IDirectiveTypeDescriptor<UpperDirective> descriptor)
{
descriptor.Name("upper");
descriptor.Location(DirectiveLocation.Field);
descriptor.Use(next => context =>
{
foreach (var directive in context.FieldSelection.Directives)
{
if (directive.Name.Value == "upper")
{
if (context.Field.Member.MemberType == System.Reflection.MemberTypes.Property)
{
var pro = context.Field.Member as PropertyInfo;
var obj = context.GetType().GetMethod("Parent").MakeGenericMethod(context.ObjectType.RuntimeType).Invoke(context, new object[0]);
var value = pro.GetValue(obj);
pro.SetValue(obj, value.ToString().ToUpper());
}
}
}
return next.Invoke(context);
});
}
}
public class UpperDirective
{
public string Name
{
get;
set;
}
}
public class ReplaceDirectiveType : DirectiveType<ReplaceDirective>
{
protected override void Configure(IDirectiveTypeDescriptor<ReplaceDirective> descriptor)
{
descriptor.Name("replace");
descriptor.Location(DirectiveLocation.Field);
descriptor.Use(next => context =>
{
foreach (var directive in context.FieldSelection.Directives)
{
if (directive.Name.Value == "replace")
{
var dir = new Dictionary<string, object>();
foreach (var item in directive.Arguments)
{
dir.Add(item.Name.Value?.ToLower(), item.Value.Value);
}
if (context.Field.Member.MemberType == System.Reflection.MemberTypes.Property)
{
var s = context.Parent<Student>();
var pro = context.Field.Member as PropertyInfo;
var obj = context.GetType().GetMethod("Parent").MakeGenericMethod(context.ObjectType.RuntimeType).Invoke(context, new object[0]);
var value = pro.GetValue(obj);
pro.SetValue(obj, value.ToString().Replace(dir["old"].ToString(), dir["new"].ToString()));
}
}
}
return next.Invoke(context);
});
}
}
public class ReplaceDirective
{
public string Old
{
get;
set;
}
public string New
{
get;
set;
}
}
}
}
upper和replace兩個Directive處理的還比較粗糙,這裏主要說明Directive的定義方式;在調用這些Directive時,按照前後順序調用,多個Directive可以同時生效,和asp.net core的中間件原理相近,上例的後兩個調用 name @upper @replace和name @replace @upper返回的結果是不一樣的。