java - JSon字符串转JSON对象？

Question

String userStr=readJSONString(request);

        System.out.println(userStr);//能输出
        JSONObject jsonObj = JSONObject.fromObject(userStr);//我感觉这有问题

        System.out.println(jsonObj.getInt("userid"));//后台没输出
        System.out.println(jsonObj.getString("username"));
        输出结果如下

Answer 1

should be JSONObject import错了，或者是版本不对吧，我本地用的是 json-lib-2.4 net.sf.json.JSONObject, which is OK.

Answer 2

If the frontend transmits json type data, then the backend receives json type data, and there is no need to transfer it anymore

Answer 3

1. First confirm whether your userStr is a json string:
For example: String jstr="{'json':'jsonvalue','bool':true,'int':1,'double':'20.5'} ";
2. Then check whether the JOSNObject you are using is the json.jar package.
3. Confirm whether your json package is imported correctly.

Answer 4

First take a look at the package introduction of the net.sf.json.JSONObject version mentioned by taomaokun, and then check whether your json string is written correctly. This is generally available