获取小程序二维码，实现PC端微信扫码登录

柔光的暖阳◎ 2024-03-24 20:52 210阅读 0赞

思路：

1.前端生成随机字符串（有数字或字母组成，最好不要有特殊字符，不是所有的特殊字符都支持）

2.PC端调用后端接口，获取小程序二维码，并开始轮询访问接口获取小程序授权的信息

3.微信扫码登录，获取包含在二维码中的参数key（上面的随机字符串），将key和用户信息作为请求参数，调用授权接口

public WxTokenResponse getToken() {
            if (wxTokenResponse != null &&
                    !StringUtils.isEmpty(wxTokenResponse.getAccessToken())) {
                Date curDate = new Date();
                int span = (int) ((curDate.getTime() - updateTime.getTime()) / 1000);
                if (span < wxTokenResponse.getExpiresIn() - 15) {
                    return wxTokenResponse;
                }
            }
    
            Map<String, Object> params = new HashMap<String, Object>();
            params.put("grant_type", "client_credential");
            params.put("appid", wxPayConfig.getAppid());
            params.put("secret", wxPayConfig.getSecret());
            wxTokenResponse = null;
            String jsonStr = apiService.invokeGet(weChartConfig.getUrl(), "cgi-bin/token", null, params);
            if (!StringUtils.isEmpty(jsonStr)) {
                wxTokenResponse = JSONObject.parseObject(jsonStr, new TypeReference<WxTokenResponse>() {
                });
                updateTime = new Date();
                return wxTokenResponse;
            }
            return null;
        }
    
    
    /**
         * 
         * @param request
         * @param resp
         * @param key
         * @param path 不传的话，默认跳转小程序的主页，只有在跳转的页面才能获得自定义的参数
         */
        public void getAppletCodeStream(HttpServletRequest request, HttpServletResponse resp, String key, String path) {
            wxTokenResponse = getToken();
           
            String accessToken = wxTokenResponse.getAccessToken();
           
            //获取小程序码
            String codeUrl = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=ACCESS_TOKEN"
                    .replace("ACCESS_TOKEN", accessToken);
            Map<String, Object> map = new HashMap<>();
            map.put("scene", key);
            if (path != null && !path.equals("")) {
                map.put("page", key);
            }
            try {
                CloseableHttpResponse response = null;
                try {
                    ObjectMapper objectMapper = new ObjectMapper();
                    HttpPost httpPost = new HttpPost(codeUrl);
                    httpPost.addHeader("Content-type", "application/json; charset=utf-8");
                    httpPost.setEntity(new StringEntity(objectMapper.writeValueAsString(map),
                            ContentType.create("text/json", "UTF-8")));
                    response = HttpClients.createDefault().execute(httpPost);
                    if (response.getStatusLine().getStatusCode() == 200) {
                        HttpEntity entity = response.getEntity();
                        if (entity != null) {
                            //这里不一定需要转为byte，根据你的项目自己选择
                            BufferedImage read = ImageIO.read(entity.getContent());
                            ImageIO.write(read, "JPEG", resp.getOutputStream());
                            
                        }
                    }
                } finally {
                    if (response != null) {
                        response.close();
                    }
                }
            } catch (Exception e) {
                LoggerUtil.logError("调用HttpUtils.sendPostRequest Exception, url=" + codeUrl + ",map=" + map, e);
            }
    
        }

private static final Map<String, UserToken> AUTH_KEY = new ConcurrentHashMap();
    
        @ApiOperation(value = "获取小程序二维码图片流", notes = "", produces = "application/json")
        @RequestMapping(value = "/getAppletCodeStream", method = RequestMethod.POST)
        public void getAppletCodeStream(HttpServletRequest request, HttpServletResponse response,
                                        @ApiParam(name = "key", value = "唯一的识别码", required = true) @RequestParam String key,
                                        @ApiParam(name = "path", value = "路径", required = true) @RequestParam String path) throws Exception {
    
            //设置相应类型,告诉浏览器输出的内容为图片
            response.setContentType("image/jpeg");
            //设置响应头信息，告诉浏览器不要缓存此内容
            response.setHeader("Pragma", "No-cache");
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expire", 0);
            response.setHeader("key", request.getSession().getId());
            wxCommonService.getAppletCodeStream(request, response, key, path);
    
        }
    
        @ApiOperation(value = "9-小程序授权登录", notes = "", produces = "application/json")
        @RequestMapping(value = "/appletPutAuth", method = RequestMethod.POST)
        public Response<String> appletPutAuth(
                @ApiParam(name = "request", value = "请求参数", required = true) @RequestBody Request<TokenQuery> request) throws Exception {
            TokenQuery entity = request.getEntity();
            ParamUtil.INSTANCE.checkObjectNull(entity, "entity")
                    .checkStrNull(entity.getKey(), "key")
                    .checkObjectNull(entity.getToken(), "token");
    
            UserToken token = entity.getToken();
            Long expire = System.currentTimeMillis() + 60 * 1000;
            token.setExpire(expire);
            AUTH_KEY.put(entity.getKey(), entity.getToken());
    
            return ResponseUtil.outSuccess();
        }
    
        @ApiOperation(value = "10-获取小程序授权", notes = "", produces = "application/json")
        @RequestMapping(value = "/getAppletAuth")
        public Response<UserToken> getAppletAuth(
                @ApiParam(name = "key", value = "唯一的识别码", required = true) @RequestParam String key) throws Exception {
            ParamUtil.INSTANCE.checkStrNull(key, "key");
            if (!AUTH_KEY.containsKey(key)) {
                throw new CustomerException("key已经过期");
            }
            UserToken userToken = AUTH_KEY.get(key);
            if (userToken.getExpire() < System.currentTimeMillis()) {
                throw new CustomerException("key已经过期");
            }
    
            AUTH_KEY.remove(key);
            return ResponseUtil.out(userToken);
        }
    
        @Scheduled(cron = "0 0/1 * * * ?")
        private void clearnAuthKey() {
    
            for (String key : AUTH_KEY.keySet()) {
                UserToken userToken = AUTH_KEY.get(key);
                if (userToken.getExpire() < System.currentTimeMillis()) {
                    AUTH_KEY.remove(key);
                }
    
            }
        }

总结：至于为什么要获取图片流直接传给前端 ，是因为获取到的小程序二维码的图片流比较大，刚开始尝试将它转成base64，却因为转出来的字符串太长被java自动添加了许多换行符，回车符，以致于转出来的图片不能显示，后来就干脆转成了图片流，前端显示也很简单使用blob就可以，参照[vue：前端接收并展示后端返回的一个图片对象（文件流）\_vue接收后端返回的对象\_奶绿走糖的博客-CSDN博客][vue_vue_-CSDN]

[vue_vue_-CSDN]: https://blog.csdn.net/ljtjianting/article/details/122458611