c# - System.Text.Json API 是否有类似 IContractResolver 的东西

Question

在新的 System.Text.Json 中；命名空间是否有类似 IContractResolver 的东西，我正在尝试将我的项目从 Newtonsoft 迁移出去。

这是我试图移动的类(class)之一:

public class SelectiveSerializer : DefaultContractResolver
{
private readonly string[] fields;

public SelectiveSerializer(string fields)
{
  var fieldColl = fields.Split(',');
  this.fields = fieldColl
      .Select(f => f.ToLower().Trim())
      .ToArray();
}

protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
  var property = base.CreateProperty(member, memberSerialization);
  property.ShouldSerialize = o => fields.Contains(member.Name.ToLower());

  return property;
}
}

Answer 1

The equivalent types in System.Text.Json -- JsonClassInfo and JsonPropertyInfo -- are internal. There is an open enhancementEquivalent of DefaultContractResolver in System.Text.Json #31257asking for a public equivalent. – dbc Nov 25 at 19:11

Github 问题:

Open up metadata infrastructure of System.Text.Json #34456

Equivalent of DefaultContractResolver.CreateProperties override in System.Text.Json #60518

Equivalent of DefaultContractResolver in System.Text.Json #31257

请试试这个:
我将其作为 System.Text.Json 的扩展编写，以提供缺少的功能: https://github.com/dahomey-technologies/Dahomey.Json 。
您将找到对编程对象映射的支持。
定义您自己的 IObjectMappingConvention 实现:

public class SelectiveSerializer : IObjectMappingConvention
{
    private readonly IObjectMappingConvention defaultObjectMappingConvention = new DefaultObjectMappingConvention();
    private readonly string[] fields;

    public SelectiveSerializer(string fields)
    {
        var fieldColl = fields.Split(',');
        this.fields = fieldColl
            .Select(f => f.ToLower().Trim())
            .ToArray();
    }

    public void Apply<T>(JsonSerializerOptions options, ObjectMapping<T> objectMapping) where T : class
    {
        defaultObjectMappingConvention.Apply<T>(options, objectMapping);
        foreach (IMemberMapping memberMapping in objectMapping.MemberMappings)
        {
            if (memberMapping is MemberMapping<T> member)
            {
                member.SetShouldSerializeMethod(o => fields.Contains(member.MemberName.ToLower()));
            }
        }
    }
}

定义你的类:

public class Employee
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
}

通过在 JsonSerializerOptions 上调用命名空间 Dahomey.Json 中定义的扩展方法 SetupExtensions 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().RegisterConvention(
    typeof(Employee), new SelectiveSerializer("FirstName,Email,Id"));

然后使用常规 Sytem.Text.Json API 序列化您的类:

Employee employee = new Employee
{
    Id = 12,
    FirstName = "John",
    LastName = "Doe",
    Email = "john.doe@acme.com"
};
        
string json = JsonSerializer.Serialize(employee, options);
// {"Id":12,"FirstName":"John","Email":"john.doe@acme.com"};