spring mvc 返回json数据的三种方式

/*
     * 返回ModelAndView类型的结果
     * 检查用户名的合法性,如果用户已经存在，返回false，否则返回true(返回json数据，格式为{"valid",true})
     */
    @RequestMapping(value = "/checkNameExistsMethod2", produces = "application/json;charset=UTF-8") //这里的produces值在不设置的情况下将根据返回结果自动决定
    public @ResponseBody
    ModelAndView checkNameValidMethod2(@RequestParam String name) {
        boolean result = true;
       //...
        Map<String, Boolean> map = new HashMap<>();
        map.put("valid", result);
        return new ModelAndView(new MappingJackson2JsonView(), map);
    }

    /*
     * 返回String类型的结果
     * 检查用户名的合法性,如果用户已经存在，返回false，否则返回true(返回json数据，格式为{"valid",true})
     */
    @RequestMapping(value = "/checkNameExistsMethod1", produces = "application/json;charset=UTF-8")
    public @ResponseBody
    String checkNameValidMethod1(@RequestParam String name) {
        boolean result = true;
        //...
        map.put("valid", result);
        ObjectMapper mapper = new ObjectMapper();
        String resultString = "";
        try {
            resultString = mapper.writeValueAsString(map);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return resultString;
    }

@RequestMapping(value = "/findEmployeebyName")
    public @ResponseBody
    Employee findEmployeebyName(String name) {
        List<Employee> lstEmployees = employeeService.getAllEmployees();
        for (Employee employee : lstEmployees) {
            if (employee.getName().equals(name))
                return employee;
        }
        return null;
    }