1. 编写目的

简单介绍微信小程序登录的实现。

2. 重要说明

由于之前做微信网页授权登录，容易被之前的思路误导。
微信小程序登录流程如官网图片：

需要说明的就是，获得用户信息并不是后端再次提交数据给微信端，获得用户信息，而是登录后在小程序内授权获得用户信息。

3. 具体代码

首先需要添加maven依赖包 httpclient 与 fastjson

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient --><dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.7</version></dependency><!-- https://mvnrepository.com/artifact/com.alibaba/fastjson --><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.56</version></dependency>

package cn.ailanglang.diary.login.controller;import com.alibaba.fastjson.JSONObject;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.client.utils.URIBuilder;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.util.EntityUtils;import org.springframework.beans.factory.annotation.Value;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import java.net.URI;/** * @author smileyan */@RestController@RequestMapping("/wechat")public class WeChatLoginController {    @Value("${wechat.appid}")    private String appid;    @Value("${wechat.appsecret}")    private String appsecret;        private String openid;    private String session_key;    @GetMapping("/index")    private String login(String code) {        // 创建Httpclient对象        CloseableHttpClient httpclient = HttpClients.createDefault();        String resultString = "";        CloseableHttpResponse response = null;        String url="https://api.weixin.qq.com/sns/jscode2session?appid="+appid+"&secret="+appsecret+"&js_code="+code+"&grant_type=authorization_code";        try {            // 创建uri            URIBuilder builder = new URIBuilder(url);            URI uri = builder.build();            // 创建http GET请求            HttpGet httpGet = new HttpGet(uri);            // 执行请求            response = httpclient.execute(httpGet);            // 判断返回状态是否为200            if (response.getStatusLine().getStatusCode() == 200) {                resultString = EntityUtils.toString(response.getEntity(), "UTF-8");            }        } catch (Exception e) {            e.printStackTrace();        }        // 解析json        JSONObject jsonObject = (JSONObject) JSONObject.parse(resultString);        session_key = jsonObject.get("session_key")+"";        openid = jsonObject.get("openid")+"";        System.out.println("session_key=="+session_key);        System.out.println("openid=="+openid);        return resultString;    }}

4. 测试方法

可以在微信开发者工具中调用js的wx.login然后获得code，用console.log(code);方法输出到控制台上，然后用浏览器访问自己后端的这个路径，就可以看到json格式的返回值。

微信小程序登录完成。

Smileyan 2019年2月27日