js java into the Chinese can not be displayed, Chinese display position (?)

Today encountered such a problem, call the java with js get request, json data obtained Chinese does not display properly, jsp files are stated utf-8 format, a lot of inquiries, found problems in the @ResponseBody

@ResponseBody default encoding format ISO-8859-1, needs to be modified, added content produces in the @GetMapping

Reference: SpringMVC @ResponseBody distortion, UTF-8 format compatible

java code

@Controller
public class ExamController {
    @Autowired
    private ExamService examService;
    
    @GetMapping(value = "/getPaper", produces = "application/json; charset=utf-8")
    @ResponseBody
    public String getPaper(HttpSession session) {
        Paper paper = null;
        try {
            paper = this.examService.getPaper();
        }catch(SystemException e){
            session.setAttribute("msg", e.getMessage());
        }catch(Exception e1) {
            e1.printStackTrace();
        }
        System.out.println(paper.toString());
        return paper.toString();
    }
}