RestTemplate rest = new RestTemplate();

String token="";
String url = "https://api.weixin.qq.com/wxa/msg_sec_check?access_token="+token;
Map<String,Object> param = new HashMap<String,Object>();
param.put("content", "特3456书yuuo莞6543李zxcz蒜7782法fgnv级完2347全dfji试3726测asad感3847知qwez到");

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);

HttpEntity requestEntity = new HttpEntity(param, headers);
ResponseEntity<byte[]> entity = rest.exchange(url, HttpMethod.POST, requestEntity, byte[].class, new Object[0]);

System.out.println(new String(entity.getBody(),"utf-8"));