public static void main(String[] args) {
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("touser", "oie5e5G_jjjb4z5JEjkf27CV14FQ");
    paramMap.put("template_id", "1G49fb3tAyhbqzLoh-WnBcv51-UKqXMbeDsOQT-c6uM");
    paramMap.put("page", "/");
    paramMap.put("data", "{\"thing1\":{\"value\":\"会议提醒\"},\"time2\":{\"value\":\"2021年8月12日 15:30\"}}");
    paramMap.put("lang", "zh_CN");
    paramMap.put("miniprogram_state", "developer");
    StringEntity entity = new StringEntity(JacksonUtils.toJsonString(paramMap), "UTF-8");
    entity.setContentType("application/json");
    HttpUriRequest httpUriRequest = RequestBuilder.post()
            .setUri("https://api.weixin.qq.com/cgi-bin/message/subscribe/send")
            .addParameter("access_token", "48_-bhIkyWJvb0vH8Kc0S95H8veVuUqhOAwI0YP8YIQKJNQjyCBzz5pETdPzmArJjK9V1f1A6ONby70asT8zhOqKNCdIWUbvGPPC5EwvFhiwL43Cz5O_PHgwEdmZ2d6-U6QGlhctzssCMf9VvvvKCAjAEAOGE")
            .setEntity(entity)
            .build();
    Map result = LocalHttpClient.executeJsonResult(httpUriRequest, Map.class);
    System.out.println(JacksonUtils.toJsonString(result));
}

测试代码如上, 日志打印如下

weixin.popular.client.LocalHttpClient    : URI[2c62b401-776a-4120-bb47-f7dcaf51de71] https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token=48_-bhIkyWJvb0vH8Kc0S95H8veVuUqhOAwI0YP8YIQKJNQjyCBzz5pETdPzmArJjK9V1f1A6ONby70asT8zhOqKNCdIWUbvGPPC5EwvFhiwL43Cz5O_PHgwEdmZ2d6-U6QGlhctzssCMf9VvvvKCAjAEAOGE Content-Type: application/json ContentLength:259 Content:{"touser":"oie5e5G_jjjb4z5JEjkf27CV14FQ","data":"{\"thing1\":{\"value\":\"会议提醒\"},\"time2\":{\"value\":\"2021年8月12日 15:30\"}}","template_id":"1G49fb3tAyhbqzLoh-WnBcv51-UKqXMbeDsOQT-c6uM","miniprogram_state":"developer","page":"/","lang":"zh_CN"}

URI[2c62b401-776a-4120-bb47-f7dcaf51de71] elapsed time:310 ms RESPONSE DATA:{"errcode":47003,"errmsg":"argument invalid! data.thing1.value is emtpy rid: 6114d3f7-146e9c54-6d9740c1"}