整体流程如下：

- 1.获取code

- 2.用步骤1获取到的临时code换取用户唯一标识OpenId和会话密钥 session_key

- 3.获取用户手机号，进行登录

请求地址：GET https://api.weixin.qq.com/sns/jscode2session?appid=APPID&secret=SECRET&js_code=JSCODE&grant_type=authorization_code

请求参数：

请求参数：

返回值：

开发前准备（必须）

appid：wx4c1d53****7a671

appsecret：fc9f99c08dcb2a0****eb26376c65eae

小程序代码：

login.js

// pages/login/login.wxml.js
const app = getApp();
Page({

  /**
   * 页面的初始数据
   */
  data: {
      // 判断小程序的API，回调，参数，组件等是否在当前版本可用。
      canIUse: wx.canIUse(\'button.open-type.getPhoneNumber\'),
      wechat: \'微信快捷登录\',
      isShow: false
  },

  /**
   * 生命周期函数--监听页面加载
   */
  onLoad: function (options) {
      // 从缓存中取手机号
      console.log("获取手机号！")
      try {
        var value = wx.getStorageSync(\'phoneNumber\')
        if (value) { // 说明已登录 跳转 页面
          console.log("获取缓存："+value)
          wx.navigateTo({
            url: \'../login?param=\' + value
          })
        }else{// 未登录 显示 微信授权页面
          this.setData({
            isShow: true
          })
        }
      } catch (e) {

      }
      // 解决第一次获取手机号失败问题
      wx.login({
        success: res => {
          if(res.code){
            console.log("code->", res.code)
          }
        }
      })
    },

      // 0.获取手机号授权
  getPhoneNumber: function(e) {
    // 用户拒绝授权
    if(e.detail.errMsg == "getPhoneNumber:fail user deny") {
      wx.showToast({
        icon: "none",
        title: \'请允许获取手机号，否则功能不可用！\',
      })
      return
    }
  //  console.log("e->detail", e.detail)
    /// 用户允许授权
    // console.log("iv->", e.detail.iv); //包括敏感数据在内的完整用户信息的加密数据,需要解密
    // console.log("encryptedData->", e.detail.encryptedData); //加密算法的初始向量，解密需要用到

    /// 获取手机号
    // 1.获取临时登录凭证code
    wx.login({
      success: res => {
        if(res.code){
          this.code = res.code;
          console.log("code->", res.code)
          console.log("encryptedData->", encodeURIComponent(e.detail.encryptedData))
          console.log("iv->", e.detail.iv)
          this.getSessionKey(res.code, e.detail.encryptedData, e.detail.iv);
        }
      }
    })
    },
  // 2.访问登录凭证校验接口获取session_key（后续改成后台实现）
  getSessionKey: function(js_code, encryptedData, iv) {
    // 3. 解密获取手机号
    wx.request({
      url: \'http://localhost:8082/wechat/appletLogin\',
      data: {
          \'encryptedData\': encodeURIComponent(encryptedData),//需要进行编码
          \'iv\': iv,
          \'jscode\': js_code
      },
      method: \'POST\', 
      header: {
          \'content-type\': \'application/json\'
      }, // 设置请求的 header
      success: function(data2) {
          var data = data2.data
          console.log(data)
          if(data.resultCode == 200) { 
            if(data.data.user.phone==undefined){
              // 获取手机号失败 跳转到 常规 用户登录页面（通过webview）
              wx.navigateTo({
                url: \'用户登录页\'
              })
              return
            }
            // 存储数据到缓存
            wx.setStorage({
              key:"phoneNumber",
              data:data.data.user.phone
            })
            // 4.跳转页面
          }
      },
      fail: function(err) {
          console.log(err);
          wx.showToast({
            icon: "none",
            title: \'获取手机号失败，请重试！\',
          })
      }
    })
  },
  

  /**
   * 生命周期函数--监听页面初次渲染完成
   */
  onReady: function () {

  },

  /**
   * 生命周期函数--监听页面显示
   */
  onShow: function () {

  },

  /**
   * 生命周期函数--监听页面隐藏
   */
  onHide: function () {

  },

  /**
   * 生命周期函数--监听页面卸载
   */
  onUnload: function () {

  },

  /**
   * 页面相关事件处理函数--监听用户下拉动作
   */
  onPullDownRefresh: function () {

  },

  /**
   * 页面上拉触底事件的处理函数
   */
  onReachBottom: function () {

  },

  /**
   * 用户点击右上角分享
   */
  onShareAppMessage: function () {

  }
})

login.json

{
  "usingComponents": {}
}

login.wxml

<!--pages/login.wxml-->
<view class="modal-mask" catchtouchmove="preventTouchMove" wx:if="{{isShow}}"></view>
  <view class="modal-dialog" wx:if="{{isShow}}">
  <view class="modal-content">
    <view><image src=\'../images/show.png\' class=\'show\'></image></view>
    <!-- <view>绑定手机号</view>
    <view>请先绑定手机号在进行此操作</view>   -->
    <button class="show" type="primary" lang="zh_CN"
    open-type=\'getPhoneNumber\' bindgetphonenumber="getPhoneNumber" >
      微信用户一键登录
    </button>
  </view>
</view>

login.wxss

/* pages/login/login.wxml.wxss */
.show{
  display: block;
  border-radius: 8rpx;
  margin: 20rpx 20rpx 20rpx 20rpx;
  font-size: 35rpx;
}

.container{
  position: fixed;  /*关键属性，设置为fixed*/
  display: flex;
  flex-direction: column;
  width: 100%;
  height: 100%;
}

后端代码

WxLoginController.java

@RestController
@RequestMapping("/wechat")
public class WxLoginController {

    private Logger logger = LoggerFactory.getLogger(WxLoginController.class);
    
    @Autowired
    UserDao userDao;
    
    @Value("${wechat.appid}")
    private String appid;
    @Value("${wechat.appsecret}")
    private String appsecret;
    
    private Map<String, Object> userMap = new HashMap<>();
    
    @GetMapping("/appletLogin")
    public ResultBean appletLogin(String encryptedData, String iv, String jscode) {
        System.out.println(encryptedData);
        ResultBean resultBean = new ResultBean();
        // jscode
        if (StringUtils.isEmpty(jscode)) {
            resultBean.setResultCode(-10001);
            resultBean.setResultMessage("鉴权失败！");
            return resultBean;
        }
        // sign
        if (StringUtils.isEmpty(encryptedData)) {
            resultBean.setResultCode(-10001);
            resultBean.setResultMessage("鉴权失败！");
            return resultBean;
        }
        if(StringUtils.isBlank(iv)) {
            resultBean.setResultCode(-10002);
            resultBean.setResultMessage("鉴权失败！");
            return resultBean;
        }

        // 创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();
        String resultString = "";
        CloseableHttpResponse response = null;
        String url =WxContants.url.replace(WxContants.APPID, appid).
                replace(WxContants.SECRET, appsecret).replace(WxContants.JSCODE, jscode);

        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);
        String session_key = jsonObject.getString("session_key");
        String openid = jsonObject.getString("openid");

        System.out.println("session_key："+session_key + ",openid："+openid);
        if (StringUtils.isEmpty(session_key)) {
            resultBean.setResultCode(-10003);
            resultBean.setResultMessage("获取sessionkey失败！");
            return resultBean;
        }

        // 解码
        try {
            encryptedData = URLDecoder.decode(encryptedData,"UTF-8");
        } catch (UnsupportedEncodingException e) {
            logger.error("encryptedData，decode失败！", e);
            resultBean.setResultCode(-10003);
            resultBean.setResultMessage("encryptedData，decode失败！");
            return resultBean;
        }
        String decryptData = WechatDecryptDataUtil.decryptData(encryptedData, session_key, iv);
        JSONObject userInfo = JSONObject.parseObject(decryptData);
        // 存入redis+数据库，判断是否存在redis中，存在直接从redis返回
        // 本地使用Map模拟
        if (!userMap.containsKey(openid)) {
            // 判断用户是否存在系统中
            String phoneNumber = userInfo.getString("phoneNumber");
            User user = userDao.findByPhone(phoneNumber);
            if (user == null) {
                resultBean.setResultCode(200);
                resultBean.setResultMessage("此用户不存在，请先注册！");
                return resultBean;
            }
            user.setOpenId(openid);
            userDao.save(user);
            userMap.put(openid, user);
        }
        User user = (User) userMap.get(openid);
        resultBean.setResultCode(200);
        resultBean.setResultMessage("成功！");
        resultBean.setData(user);
        return resultBean;
    }
}    

UserDao.java

public interface UserDao extends JpaRepository<User, Long> {

    User findByPhone(String phone);

    User findByOpenId(String openId);
}

User.java

@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String openId;
    private String phone;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getOpenId() {
        return openId;
    }

    public void setOpenId(String openId) {
        this.openId = openId;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

WechatDecryptDataUtil.java

public class WechatDecryptDataUtil {
	private static Logger logger = LogManager.getLogger(WechatDecryptDataUtil.class);

    public static void main(String[] args) {
        String result = decryptData(
                "BLY05rL1qLzGdqn+m4s4KfnM9CbMCm2sTZmgIcUJUpoOVeZkKKYh06ATVm2BgX8HUsH1a93811fhwr70MTh2Pk2qw9rPBzvos3husUJdVfaZgBk3Afp6wNFS0/kcoyt+7q2eMrIHMe6wkc4J0hgbbkxdUwZag/pyKXwe4pUzSQfta7dfBHy3DLu+REvwHiDNfvI3KJbZ0l8/9vRjfSmT4Q==",
                "C9Z59YjFkCDT8+9NQ3OxcA==",
                "oOWTpbZ80evG/GQqRdUu3w=="
        );
        System.out.println("result = " + result);
    }

    public synchronized static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
    	String res = null;
    	try {
    		res = new String(
                    decryptOfDiyIV(
                            Base64.decode(encryptDataB64),
                            Base64.decode(sessionKeyB64),
                            Base64.decode(ivB64)
                    )
            );
		} catch (Exception e) {
			logger.error("encryptDataB64:"+encryptDataB64+"\n"+"sessionKeyB64:"+sessionKeyB64+"\n"+"ivB64:"+ivB64);
		}

        return res;
    }

    private static final String KEY_ALGORITHM = "AES";
    private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
    private static Key key;
    private static Cipher cipher;

    private static void init(byte[] keyBytes) {
        // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
        int base = 16;
        if (keyBytes.length % base != 0) {
            int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
            byte[] temp = new byte[groups * base];
            Arrays.fill(temp, (byte) 0);
            System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
            keyBytes = temp;
        }
        // 初始化
        Security.addProvider(new BouncyCastleProvider());
        // 转化成JAVA的密钥格式
        key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
        try {
            // 初始化cipher
            cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 解密方法
     *
     * @param encryptedData 要解密的字符串
     * @param keyBytes      解密密钥
     * @param ivs           自定义对称解密算法初始向量 iv
     * @return 解密后的字节数组
     */
    private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
        byte[] encryptedText = null;
        init(keyBytes);
        try {
            cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
            encryptedText = cipher.doFinal(encryptedData);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return encryptedText;
    }

}

WxContants.java

public interface WxContants {

    String APPID = "APPID";
    String SECRET = "SECRET";
    String JSCODE = "JSCODE";
    String TRADE_TYPE = "JSAPI";
    String url = "https://api.weixin.qq.com/sns/jscode2session?appid=APPID&secret=SECRET&js_code=JSCODE&grant_type=authorization_code";
}