Solution to using json.tojsonstring to display question marks in Chinese in Servlet

problem ：

stay Servlet Use in fastjson Will pass through

JSON.toJSONString()

Method to convert the object to JSON After the string , stay IDEA The converted data printed in Chinese is normal , But the client and web Among the data received , Chinese is displayed as a question mark ?. What's going on here ？

Problem analysis ：

I believe what I thought at the first time was that there was a problem with transcoding . So in which link did the transcoding go wrong ？
Because in IDEA The console prints the converted JSON The string is displayed normally , You may feel that the returned data should also be normal , But in the use of

response.getWriter().write(jsonString);

After outputting the data to the client , The data received by the client is indeed the question mark displayed in Chinese ?. So at this time, we should consider whether we are using

response.getWriter().write(jsonString);

There is something wrong with the output . In fact, the problem lies here . So how to solve it ？

resolvent ：

After analyzing the problem , Roughly determine the location of the problem , Then it's easy to solve .
Here are two solutions .

Scheme 1 ：

We know that Chinese garbled code may appear when the client transmits parameters to the background , The corresponding solution is right request Deal with it accordingly , For example, deal with post The Chinese garbled code of request parameters can be set as follows ：

request.setCharacterEncoding("UTF-8");

Sending data to the client uses response, that response Is there such a method ？ The answer is clearly yes , So you can set ：

response.setCharacterEncoding("UTF-8");

To solve the problem of Chinese garbled code when sending data to the client .

Option two ：

In fact, there is another way to solve , Is set response Of contentType as follows ：

response.setContentType("text/html;charset=utf-8");

It can also solve the problem of Chinese garbled code when sending data to the client .
Last , I hope I can help code friends in need .