在dart:io中使用json content-type的Http POST请求

Question

如何使用控制台dart应用程序执行HTTP POST(使用dart:io或可能是package:http库.我这样做:

import 'package:http/http.dart' as http;
import 'dart:io';

  http.post(
    url,
    headers: {HttpHeaders.CONTENT_TYPE: "application/json"},
    body: {"foo": "bar"})
      .then((response) {
        print("Response status: ${response.statusCode}");
        print("Response body: ${response.body}");
      }).catchError((err) {
        print(err);
      });

但是得到以下错误:

Bad state: Cannot set the body fields of a Request with content-type "application/json".

Answer 1

这是一个完整的例子.您必须使用json.encode(...)将请求的主体转换为JSON.

import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:io';


var url = "https://someurl/here";
var body = json.encode({"foo": "bar"});

Map headers = {
  'Content-type' : 'application/json', 
  'Accept': 'application/json',
};

final response =
    http.post(url, body: body, headers: headers);
final responseJson = json.decode(response.body);
print(responseJson);

通常建议您使用a Future来满足您的要求,这样您就可以尝试类似的东西

import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:io';

Future<http.Response> requestMethod() async {
    var url = "https://someurl/here";
    var body = json.encode({"foo": "bar"});

    Map<String,String> headers = {
      'Content-type' : 'application/json', 
      'Accept': 'application/json',
    };

    final response =
        await http.post(url, body: body, headers: headers);
    final responseJson = json.decode(response.body);
    print(responseJson);
    return response;
}

语法的唯一区别是async和await关键字.

Answer 2

来自http.dart:

/// [body] sets the body of the request. It can be a [String], a [List<int>] or
/// a [Map<String, String>]. If it's a String, it's encoded using [encoding] and
/// used as the body of the request. The content-type of the request will
/// default to "text/plain".

所以自己生成JSON主体(使用JSON.encodefrom dart:convert).