public Map gen(String accessToken) {
RestTemplate rest = new RestTemplate();
    InputStream inputStream = null;
    OutputStream outputStream = null;
    try {
        String url = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token="+accessToken;
        Map<String,Object> param = new HashMap<>();
        param.put("scene", "");
        param.put("page", "pages/index/index");
        param.put("width", 430);
        param.put("auto_color", false);
        Map<String,Object> line_color = new HashMap<>();
        line_color.put("r", 0);
        line_color.put("g", 0);
        line_color.put("b", 0);
        param.put("line_color", line_color);
       
        MultiValueMap<String, String> headers = new LinkedMultiValueMap<>();
        HttpEntity requestEntity = new HttpEntity(param, headers);
        ResponseEntity<byte[]> entity = rest.exchange(url, HttpMethod.POST, requestEntity, byte[].class, new Object[0]);
        byte[] result = entity.getBody();
        
        FileOutputStream fs = new FileOutputStream("C:/Users/Administrator/Desktop/1.jpg");
        FileCopyUtils.copy(new ByteArrayInputStream(result), fs);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
    
    }
    return null;
}