public WxSimpleResult addKfAccountTest() {
        // my_access_value 是我的 access_token 的值
        String url = "https://api.weixin.qq.com/customservice/kfaccount/add?access_token=my_access_value";
        
        HttpHeaders httpHeaders = new HttpHeaders();
        // Json 穿擦
        httpHeaders.setContentType(MediaType.APPLICATION_JSON);


        
        // 第一中请求方式
        HashMap<String, String> parameters = new HashMap<>();
        // 我添加的客服微信的账号
        parameters.put("kf_wx", "my_wx_account_value");
        HttpEntity<HashMap<String, String>> entity = new HttpEntity<>(parameters, httpHeaders);
        //  class WxSimpleResult 对象字段结构如：{"errcode":0,"errmsg":"ok"}
        ResponseEntity<WxSimpleResult> response = restTemplate.postForEntity(url, entity, WxSimpleResult.class);




        // 第二种请求方式
        MultiValueMap<Object, Object> body2 = new LinkedMultiValueMap<>();
        body2.add("kf_wx", "my_wx_account_value");
        HttpEntity<MultiValueMap<Object, Object>> entity2 = new HttpEntity<>(body2, httpHeaders);
        ResponseEntity<WxSimpleResult> response2 = restTemplate.postForEntity(url, entity2, WxSimpleResult.class);




        // 第三中请求方式，使用对象包装参数（ AddKfRequest 类中字段 kf_wx,business_id）
        AddKfRequest body3 = AddKfRequest.create("my_wx_account_value", null);
        HttpEntity<AddKfRequest> entity3 = new HttpEntity<>(body3, httpHeaders);
        ResponseEntity<WxSimpleResult> response3 = restTemplate.postForEntity(url, entity3, WxSimpleResult.class);


        return null;
}
*** 以上三种参数封装方式传参 都响应 412 Precondition Failed: [no body]  ***

// #######################  参数和返回值实体类 #############################
// 返回值接收对象
@Getter
@Setter
public class WxSimpleResult implements Serializable {
    @Serial
    private static final long serialVersionUID = 1L;
    /**
     * 错误响应码,成功时返回 0
     *
     */
    private Integer errcode;
    /**
     * 错误响应消息,成功时返回 ok
     */
    private String errmsg;
}
// 请求参数对象
@Getter
@Setter
public class AddKfRequest implements Serializable {
    @Serial
    private static final long serialVersionUID = 1L;
    private String kf_wx;
    private Integer business_id;


    public static AddKfRequest create(String kfWx, String businessId) {
        AddKfRequest addKfRequest = new AddKfRequest();
        addKfRequest.setKf_wx(kfWx);
        if (null != businessId && !businessId.isBlank()) {
            addKfRequest.setBusiness_id(Integer.valueOf(businessId));
        }
        return addKfRequest;
    }

}

代码截图如下：

********** 如上三种 参数封装的方式请求，均为异常响应 412 Precondition Failed: [no body] *********