使用 JavaScript 的 Fetch API 发送 POST 请求时 JSON 解析错误

Question

When I send the following POST request using fetch:

                fetch(requestUrl, {
                    method: 'POST',
                    headers: {
                        'id': 'my_id',
                        'secret': 'my_secret',
                        'Content-Type': 'application/json'
                    },
                    body: {
                      'username': '123',
                      'password': '456'
                    }
                })
                .then(function(response) {
                    return response.json();
                })
                .then(function(data) {
                    console.log(data);
                })
                .catch((error) => {
                    console.log(error);

                })

I get the following error:

   'JSON parse error: Unrecognized token \'object\': was expecting (\'true\', \'false\' or \'null\'); nested exception is com.fasterxml.jackson.core.JsonParseException: Unrecognized token \'object\': was expecting (\'true\', \'false\' or \'null\')\n at [Source: java.io.PushbackInputStream@f402d7e; line: 1, column: 9]',

I tried troubleshooting, and the error is caused by my headers and body that I'm trying to send with the request.

Does anyone know what exactly the error is related to?

Answer 1

JSON starts either with a { or a [ or a normal ascii char. You trying to do some kind of Mess and so the JSON parser is confused. No valid JSON no fun. It would be also helpful to show us the first few chars of the thing what you either send or what you receive before it happens. The JSON string HAS to be correct according JS documentation. If you try to send special chars like ]}\,'" inside the data sets it will also mix it up. In this case you has to escape those characters. If nothing help make a base64 string of the values. I just can guess that you has noot escaped the "\" char (should look like \ \ escaped ) or did you mean '\object\'? This looks a bit strange as you show it (wrong ' position at start). Some online JSON decoders also gives more helpful information on errors.The error is in anycase inside the JSON string. If some "header" would be wrong - nothing would be returned.