前言

最近在做小程序相关的项目，之前也在网上找过很多资料，遇到不少坑，和大家分享一下成果。

简介

小程序获取二维码有官网三种接口：

POST https://api.weixin.qq.com/cgi-bin/wxaapp/createwxaqrcode?access_token=ACCESS_TOKEN：获取小程序二维码，适用于需要的码数量较少的业务场景。
POST https://api.weixin.qq.com/wxa/getwxacode?access_token=ACCESS_TOKEN：获取小程序码，适用于需要的码数量较少的业务场景。
POST https://api.weixin.qq.com/wxa/getWXACodeUnlimit?access_token=ACCESS_TOKEN：获取小程序码，适用于需要的码数量极多的业务场景。
这三种方案前提都是要获取access_token，大家可根据各自需求选择。

获取access_token

核心代码如下：

private static AppletTokenResult getAppletToken(String key){AppletTokenResult tokenResult = new AppletTokenResult();String getaccess_tokenurl = "https://api.weixin.qq.com/cgi-bin/token?" +"grant_type=client_credential" +"&appid=" + APPID +"&secret=" + SECRET;RestTemplate restTpl = new RestTemplate();String tokenDataStr = restTpl.getForObject(getaccess_tokenurl, String.class);if(StringUtil.isEmpty(tokenDataStr)){throw new CommonException("小程序获取token失败！");}tokenResult = new Gson().fromJson(tokenDataStr, AppletTokenResult.class);if(StringUtil.isEmpty(tokenResult.getAccess_token())){throw new CommonException("小程序获取token失败！");}int expire = 2 * 60 * 55;int temp = tokenResult.getExpires_in();expire = temp == 0 ? expire : temp- 5 * 60;redisCache.put(key, (Serializable) tokenResult, expire);return tokenResult;}

AppletTokenResult类定义请求微信平台access_token返回信息：

import java.io.Serializable;/** * 小程序获取token返回数据 * @author 0200759 * */public class AppletTokenResult implements Serializable{/** *  */private static final long serialVersionUID = 2537928824643088525L;/** * 小程序token */private String access_token;/** * token有效时间 */private int expires_in;public int getExpires_in() {return expires_in;}public void setExpires_in(int expires_in) {this.expires_in = expires_in;}public String getAccess_token() {return access_token;}public void setAccess_token(String access_token) {this.access_token = access_token;}}

由于小程序token存在有效时间，超过这个时间需要重新从微信平台取，我这里把token放入redis缓存里并设置了缓存有效时间(比小程序token有效时间略小)。

获取二维码

代码如下：

/** * 小程序接口 * @author 0200759 * */@Controller@RequestMapping("/applet")public class AppletController {/** * @param res * 调用二维码接口2(https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=ACCESS_TOKEN) */ @RequestMapping("/getQRCode") public void getQRCode(HttpServletResponse res) {        RestTemplate rest = new RestTemplate();        InputStream inputStream = null;        try {        AppletTokenResult appletTokenResult = CacheAppletUtil.get(Constants.APPLET_TOKEN);        if(appletTokenResult == null || StringUtil.isEmpty(appletTokenResult.getAccess_token())){        throw new CommonException("小程序token获取失败！");        }            String url = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token="              +appletTokenResult.getAccess_token();            Map<String, Object> param= new HashMap<String, Object>();            param.put("scene", "xxxx");            param.put("page", "pages/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);            HttpHeaders headers = new HttpHeaders();            headers.setContentType(MediaType.APPLICATION_JSON);            HttpEntity<String> requestEntity = new HttpEntity<String>(new Gson().toJson(param), headers);            ResponseEntity<byte[]> entity = rest.exchange(url, HttpMethod.POST,             requestEntity, byte[].class, new Object[0]);            byte[] result = entity.getBody();            inputStream = new ByteArrayInputStream(result);                        IOUtils.copy(inputStream, res.getOutputStream());        } catch (Exception e) {            new CommonException("调用小程序生成微信永久小程序码URL接口异常!");        } finally {            if(inputStream != null){                try {                    inputStream.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

这里使用的二维码方式是方案三getwxacodeunlimit，有以下几点需注意：