1、axios请求提交数据

const headers = {
    'Content-Type': 'text/plain'
};
var json = '{"json_data":"{\"value\":\"hello world\"}';
axios.post('test', json, { headers: headers })
    .then(function (response) {alert(response)}

2、后台接收POST数据API

1）API方法

[ApiController]
[Route("[controller]")]
public class TestController : ControllerBase
{
    [HttpPost]
    public async Task<IActionResult> Post([FromBody]string json)
    {
        return this.Ok();
    }
}

2）使用自定义纯文本输入格式化器

public class TextPlainInputFormatter : TextInputFormatter
{
    public TextPlainInputFormatter()
    {
        SupportedMediaTypes.Add("text/plain");
        SupportedEncodings.Add(UTF8EncodingWithoutBOM);
        SupportedEncodings.Add(UTF16EncodingLittleEndian);
    }
    protected override bool CanReadType(Type type)
    {
        return type == typeof(string);
    }
    public override async Task<InputFormatterResult> ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)
    {
        string data = null;
        using (var streamReader = new StreamReader(context.HttpContext.Request.Body))
        {
            data = await streamReader.ReadToEndAsync();
        }
        return InputFormatterResult.Success(data);
    }
}

3）在ConfigureServices(IServiceCollection services) 中添加配置

services.AddControllers(opt => opt.InputFormatters.Insert(0, new TextPlainInputFormatter()));